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Title: Ophthalmology lecture notes
Description: A very comprehensive and detailed set of notes covering all aspects of ophthalmology. Complete with a nice set of diagrams to aid learning. Useful for medical students.
Description: A very comprehensive and detailed set of notes covering all aspects of ophthalmology. Complete with a nice set of diagrams to aid learning. Useful for medical students.
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OPTHALMOLOGY LECTURE NOTES
VISUAL PATHWAYS
The retina is a light-‐sensitive layer of tissue, lining the inner surface of the eye
...
Light striking the retina initiates a cascade of chemical and electrical events that ultimately
trigger nerve impulses
...
This information is then processed and results in “vision”
...
The
only neurons that are directly sensitive to light are the photoreceptor cells
...
Rods function mainly in dim light (scotropic) and provide black-‐and-‐white
vision, while cones support daytime vision (phototropic) and the perception of colour
...
g pupillary light reflex) and also transmits information to the suprachiasmatic nuclei in
the hypothalamus (important for the bodies master circadian rhythm)
...
g
...
Several important features of visual
perception can be traced to the retinal encoding and processing of light
...
However, they are not sensitive to colour
...
Rods are primarily responsible for night/low light vision (scotopic vision) and black and
white vision
...
Cones mediate day
vision (photopic vision) and are sensitive to one of three different colors (green, red or
blue)
...
3 mm diameter rod-‐free area
with very thin, densely packed cones
...
The fovea
is responsible for sharp central vision (also called foveal vision), which is necessary in
humans for reading, driving, and any activity where visual detail is of primary importance
...
Approximately 50% of the nerve fibers in the optic nerve carry information from the fovea
(macula region), while the other 50% carry information from the rest of the retina
...
In the fovea, there are very few rods (with none at the
foveola)
...
The cones are also packed closer together here in the
fovea than in the rest of the retina
...
It comprises less than 1% of retinal size but takes up over 50% of the visual cortex in the
brain
...
If an object is large and thus covers a large angle,
the eyes must constantly shift their gaze to subsequently bring different portions of the
image into the fovea (as in reading)
...
This
allows the light to be sensed without any dispersion or loss e
...
so light has a direct path to
the photoreceptors
...
• The high spatial density of cones along with the absence of blood vessels at the fovea
accounts for the high visual acuity capability at the fovea
...
2 mm in diameter) -‐ a central pit where only
cone photoreceptors are present and there are virtually no rods
...
• At the foveola there is a unique 1 cone: 1 bipolar cell : 1 ganglion cell connection
...
We are not aware of this because
we instinctively direct our center of gaze to where we are looking
...
•
There are very few rods in the fovea and at the foveola, there are no rods at all
...
•
Moreover, in the fovea, the retinal ganglion cells have smaller receptive fields (therefore
better spatial resolution, occurs due to unique 1 cone to 1 bipolar cell conection), and in the
periphery, they have much larger receptive fields (multiple cones/rods synapse onto single
ganglio cell via bipolar neurones)
•
Curiously, despite the vitality of cones to our vision, we have 125 million rods and only 6
million cones
...
The peak density of cones is in our fovea
...
•
The fact that our vision has the highest acuity in the center of gaze does not mean that our
vision in the rest of the visual field is inferior -‐ it’s simply used for different things
...
•
Our foveal vision is optimized for fine details, and our peripheral vision is optimized for
coarser information
...
It receives visual information from
photoreceptors via two intermediate neuron types: bipolar cells and amacrine cells
...
g
...
•
Retinal ganglion cells vary significantly in terms of their size, connections, and responses to
visual stimulation but they all share the defining property of having a long axon that extends
into the brain
...
•
A small percentage of retinal ganglion cells contribute little or nothing to vision, but are
themselves photosensitive; their axons contribute to circadian rhythms and pupillary light
reflex
...
•
The appearance of an object depends primarily on the contrast between the object and its
background-‐ not the intensity of the light source
...
g
...
It can also be thought of as an "area in which
stimulation leads to response of a particular sensory neuron"
•
In the fovea, each ganglion cell only receives input from one cone (via a bipolar cell) which
results in a small receptive field
...
g
...
The receptive field of the
ganglion cell consists of information from many rods and cones e
...
the brain receives less
high spatial frequency information => lower visual acuity
•
The size of the receptive field governs the spatial frequency of the information: small
receptive fields (e
...
in the fovea) are stimulated by high spatial frequencies which provides
fine detail information; large receptive fields are stimulated by low spatial frequencies,
which provide coarse detail information
...
Therefore
small receptive fields are better at distinguishing finer details (analogous to smaller sensory
receptive fields in finger tips being able to sense fine discriminatory touch)
Central Visual Pathways
The retinal image and the visual field are not the same e
...
due to lens inversion
Retina is divided at the midline (fovea):
•
Nasal hemiretina (medial to the fovea) which receives the ipsilateral hemifield
•
Temporal hemiretina (lateral to fovea) which receives the contralateral hemifield
Retina is sub-‐divided into:
•
Superior quadrant
•
Inferior quadrant
The “visual field” is the view seen by the two eyes without movement of the head
•
The left and right halves of the field are simply defined when the foveas are fixed on a single
point
...
•
The pink dot (right half of the visual field) is imaged on the nasal (N) portion of the right eye
and the temporal portion (T) of the left eye
...
•
In mammals with forward facing eyes, e
...
primates and carnivores, the majority of axons
carrying information from the temporal retina projects ipsilaterally (i
...
does NOT
decussate) (light blue and pink) and those from the nasal retina decussate and travel
contralaterally (dark blue and pink)
...
g
...
•
Therefore the right visual field is received by the left visual cortex, and the left visual field
is received by the right visual cortex (as a result of the decussating and non-‐decussating
paths)
•
After the optic chiasm, the optic tracts feed into the dorsal lateral geniculate nucleus
(dLGN) of the thalamus, wehere the axons segregate into eye specific zones
...
Central projections from the retina
•
Axons of ganglion neurones exit the retina at the optic disc
•
They then become myelinated and form the optic nerve
•
The optic nerve (CN II) and retina is part of the CNS, developing as an outgrowth of the
ventral diencephalon (the optic nerve is commonly misclassified as a peripheral nerve)
•
The optic nerves travel to the optic chiasm where the axons are sorted and rearranged
(after decussation) into the optic tracts
The optic tracts project to subcortical regions in the brain
•
The optic tracts project to subcortical regions in the brain e
...
LGN of thalamus, pretectum
of midbrain and superior collicilus
•
Lateral Geniculate Nucleus of the thalamus: processes information and projects onto the
primary visual cortex via optic radiations
...
•
Pretectum (midbrain structure): controls pupillary reflexes e
...
The
pretectum area communicates bilaterally with the Edinger–Westphal nuclei (accessory
parasympathetic cranial nerve nuclei of the oculomotor nerve CN III) to bring about the
bilateral pupil reflexes
...
•
During development, each axon must therefore make an unerring decision about which side
of the brain to innervate when it reaches the optic chiasm!
•
Rememeber that the visual cortex receives an inverted image of the world due to lens
inversion – it then anti-‐inverts it!
•
It is also important to remember that the retina receives an inverted image of the real workd
– therefore a lesion of the superior retina will result in a lower visual field defect
The Lateral Geniculate Nucleus (LGN)
•
The Lateral Geniculate Nucleus (LGN) of the thalamus is the principal terminus for input to
the visual cortex
...
•
Approximately 90% of axons from the retina terminate in the LGN
•
Without this pathway visual perception is absent
•
In each LGN there is retinotopic representation of the the contralateral half of the visual
field
...
•
The fovea has the greatest density of ganglion cells and has a relatively greater
representation than does peripheral regions of the retina
•
The receptive fields of the LGN have a similar organization to that of retinal ganglion
neurones – concentric receptive fields with an antagonistic centre-‐surround measuring
contrast in light intensity
...
Receptive fields in the visual cortex
•
Neurones in V1 (primary visual cortex) respond to line or bar stimuli
•
Achieved by decomposing the outlines of a visual image into short line segments of various
orientations
...
•
Receptive fields of cells (simple) in the primary visual cortex are narrow elongated zones
with flanking zones of excitation or inhibition
...
A saccade is a fast eye motion, and because it is a motion
that is optimised for speed, there is inevitable blurring of the image on the retina, as the
retina is sweeping the visual field
...
Humans become effectively blind
during a saccade
...
•
Fixation intervals between saccades in which gaze is held almost stationary and fixated at
the point of interest
•
The saccade-‐fixation eye movements allow us to redirect our central vision rapidly to a
region of interest (for high visual acuity) and are visually directed
•
Why? Fovea has an astonishingly small angular diameter (0
...
025% of retinal surface
•
To see what we are looking at in detail require to move the eye so that object is centred on
the fovea
...
This is a closed velocity feedback loop
Gaze
•
The objective of the gaze control system is to move the eyes relative to space so that the
fovea, or line of sight, is placed and subsequently kept on a target of interest
...
•
Gaze = eye-‐in-‐head + head-‐in-‐space
•
The superior colliculus controls the direction and the amplitude of the entire gaze shift
Pretectal region
•
The pretectal region of the midbrain (mesencephalon) controls pupillary reflexes
•
Light shining in one eye causes constriction of both the ipsilateral pupil (direct response) and
contralateral pupil (consensual response)
•
The neural pathway mediating pupillary light reflexes starts in the retinal photosensitive
ganglion neurones that project to the midbrain (pretectum)
•
The neurones in this area project bilaterally to the pre-‐ganglioninic parasympathetic
neurones in the accessory CN III occulomotor nucleus (Edinger-‐Westphal nucleus)
•
The efferent outflow is in the occulomotor nerve (Cranial nerve III) to the ciliary ganglion
then onto and muscles of the iris (contrictor pupillae) via postganglion fibre
...
Similarly the consensual response will also be absent in
the left eye
...
May also have a blown out pupil (CN III nuclei damage)
...
•
Characteristic deficits in the visual field are associated with lesions at specific sites
1
...
Lesion in the optic chiasm results in loss of vision in the temporal halves of the visual fields-‐ a
bitemporal hemianopia
...
3
...
Left homonymous hemianopia due to lesion or pressure on right optic tract
...
g
...
No macular sparing
...
Left homonymous inferior quadrantanopia due to involvement of upper (due to lens inversion)
right optic radiations
...
6
...
No macular sparing
...
Left homonymous hemianopia due to lesion of right occipital lobe (primary visual cortex)
...
The periphery
is much less represented and therefore more easily destroyed by an individual lesion
...
NB: After processing in the Lateral Geniculate Nucleus (LGN) of the thalamus, axons representing
both retinas (from the same visual field) mix in the optic radiation
...
This is because the axons are dispersed in the optic radiations, resulting in partial or
incomplete defects in the contralateral visual hemifield
...
•
Accommodation acts like a reflex, but can also be consciously controlled
...
Note that the refractive power of the cornea is fixed
...
It is dependent on cranial nerve II (afferent limb of
reflex), superior centres, and cranial nerve III (parasympathetic innervations of the pupil
and ciliary muscles)
...
For example,
accommodation allows the eye to focus up close
...
•
To maintain stereoscopic vision for close objects the following processes have to occur:
! Accommodation (lens accommodation): The curvature of the lens is increased
(becomes more convex => greater convergence) producing accommodation
(increase of lens +ve dioptre power)
! Miosis (pupil accommodation): The pupil constricts (miosis) to mask the poor
image forming edges of the lens and increase a depth of field
...
•
The reflex, controlled by the parasympathetic nervous system, involves three responses;
pupil accommodation (miosis), lens accommodation (increase in lens +ve dioptre power
due to increasing convexity of lens), and convergence (vergence of eyes)
•
So we look for vergence and miosis – and also ASK the pt if they can still focus on the near
object
...
Changes in contraction of the ciliary muscles alter the focal distance (and
thus power) of the eye (lens), causing nearer or farther images to come into focus on the
retina; this process is known as accommodation
...
When moving focus from a distant to a near object, the
eyes converge
...
The pupil constricts in order to prevent diverging light rays from hitting the
periphery of the retina and resulting in a blurred image
...
(a) Schematic representation of suspensory ligaments extending from the ciliary muscle to the outer
edge of the lens
...
(d) When the ciliary muscle is contracted
(parasympathetic innervations), the suspensory ligaments become slack, reducing the tension on the
lens
...
Pupillary light reflex
•
•
Afferent = RETINA and CN II (optic nerve)
•
Efferent = CN III (oculomotor – parasympathetic fibres)
•
The pupillary light reflex is an automatic luminance control mechanism
...
•
The crystalline lens is a transparent, biconvex (convergent lens with a positive power)
structure in the eye that, along with the cornea, helps to refract light to be focused on the
retina
...
This adjustment of the lens is known as lens
accommodation
...
•
The iris is a thin, circular structure in the eye, responsible for controlling the diameter and
size of the pupil (aperture) and thus the amount of light reaching the retina
...
"
•
In optical terms, the pupil is the eye's aperture and the iris is the aperture stop
...
Refraction by convex and concave lenses
•
A lens with a convex surface (normal shape of lens in eye) will converge the rays (brings
them closer together)
...
g
...
Concave
lens have negative dioptre powers => diverge rays
•
The crystalline lens of the eye is a transparent, biconvex structure in the eye that, along with
the cornea, helps to refract light to be focused (converged) onto the retina
...
This adjustment of the lens is known as lens
accommodation
...
•
Power is proportional to 1/focal length (e
...
power is inversely proportional to focal length),
therefore increasing the convexity => decrease in focal length => increase the power
(positive power)
...
The lens can then assume a
stronger, rounder shape (more convex) because of its elasticity => decrease in focal length
=> increase the power (positive power) i
...
increase the +ve dioptre power
...
The lens is more flat on its anterior side than on its posterior side
...
External lens (glasses or contact lens) can be concave and diveregent (-‐ve dioptre
power)
...
•
A
...
•
B
...
A longer distance is required for a lens of a given strength to bend the
diverging rays from a near light source into focus compared to the parallel rays from a
distant light source
...
•
C
...
g
...
Basically this states that a
light ray entering a denser medium (higher refractive index) is bent towards a line
perpendicular to the surface
...
•
Parallel rays passing into a denser medium with a convex surface or less dense medium with
a concave surface are brought into focus as a function of:
! radius of curvature (determinant of focal length)
! ratio of refractive indices of the media
...
The corneas power is fixed (although provides largest refractive component),
whereas the lens can alter its power (through accommodation)
...
34
...
42
...
Dioptre units (D) are used to describe the refractive power of a lens (characterized as
1/focal length of the lens in metres => small focal lengths have large powers)
...
A 20
dioptre lens brings parallel rays of light to focus at 1/20 metre
...
•
The refractive power of the cornea alone is approximately 40-‐44 dioptres (not adjustable)
•
It is the variable refractive power of the lens which allows accommodation (changing of
lens dioptre power) to focus on distant and near objects
...
This ability to
adjust focus is called “accommodation
...
People over the age of 25 can
only increase the power by 10 diopters
...
This severe natural deterioration is what doctors call
presbyopia (age related longsightedness/hyperopia) e
...
as we age we get progressively
worse vision at looking at objects up close due the diminished ability to increase the power
of the lens (loss of accommodation)
...
Mammals, birds
and reptiles vary the optical power by changing the form of the elastic lens using the ciliary
body (in humans up to a maximum of 20 diopters in youth) which is under parasympathetic
(CN III) control
•
Lens is held between the zonules of Zinn (ring of fibrous strands connecting the ciliary body
with the crystalline lens of the eye)
•
The ciliary body is the circumferential tissue inside the eye composed of the ciliary muscle
(intra-‐ocular muscle) and ciliary processes
...
It changes the shape of the lens within
the eye, not the size of the pupil which is carried out by the sphincter pupillae and dilator
pupillae muscles of the iris
...
Contraction of the ciliary muscles
results in the suspensory ligaments (of the zonules of ZInn) to relax and the radial tension
around the lens is released-‐ allowing the natural tension of the lens to manifest
...
Refractive error disorders
•
It’s critical that the lens system is matched to the size of the eyeball
•
Emmetropia = normal eye where a far source focused on retina without accommodation
and a near source focused on retina with accommodation
•
Myopia = Short-‐sightedness (e
...
problems with distant vision): Eyeball too long or lens is
too strong
...
Near source focused on retina with accommodation
...
g
...
•
Hypermetropia (hyperopia) = Long-‐sightedness (problems with near vision): Eyeball too
short or lens is too weak
...
Corrected with convergent
convex lens (positive power e
...
Corrected with convex lens (positive power e
...
This process allows the eye to focus on near objects
...
The suspensory ligaments relax and the radial tension around the lens is released-‐ allowing
the natural tension of the lens to manifest
...
•
The maximum refractive power of the lens is approximately 20 dioptres in youth (which
gradually declines with age)
•
The focusing power of the lens is variable, its focal length range is limited by its elasticity and
the contractile power of the ciliary muscles
...
•
Correspondingly, the furthest point that can be focused on the retina is referred to as the far
point
...
07m and Y=infinity, thus the
amplitude of accommodation is 14 dioptres
...
To move closer than 9m the
curvature of the lens has to increase e
...
the lens becomes more convex
...
Summary
•
Light is refracted in the eye (by the cornea and lens)
•
Most of that refraction in the eye takes place at the first surface (cornea), since the
transition from the air into the cornea is the largest change in index of refraction which the
light experiences
...
•
However, while the inner lens is the smaller portion of the refraction, it is the total source
of the ability to accommodate the focus of the eye for the viewing of close objects
...
•
The lens focuses an inverted image on the retina and photoreceptors
•
Image formation has physical limitations
•
Visual defects include
! Myopia (short sightedness with a long eye) which is corrected with divergent
concave (negative power) lens
! Hypermetropia (hyperopia or long sightedness with a short eye) which is
corrected with a convergent convex (positive power) lens
! Presbyopia (age related longsightedness): With age the elastic properties of the
lens deteriorate so that the amplitude of accommodation is reduced
...
Therefore, most adults need reading
glasses (convergent convex lens with positive power) at age 40-‐45
...
The visual image (inverted) from the lens is
focused on the retina with minimal distortion
...
This
functions to absorb light which prevents light not captured by the retina being reflected
back
...
In addition, the fovea
region is avascular to enhance central visual acuity
...
There are no photoreceptors in this
region therefore we have a blind spot in the visual field
...
The retina has 3 classes of neurones
•
Photoreceptors: rods, cones and photosensitive ganglion cells
•
Interneurones which process signals from photoreceptors: bipolar, horizontal and amacrine
cells
•
Ganglion cells: output of retina whose axons form the optic nerve
Rods and cones are not evenly distributed across the retina
•
Cones are most densely packed in the fovea but still found at a reasonable density in the
periphery
...
Many rods are found in the periphery (and indeed are
the most numerous retinal neurone in total) and are most densely packed 12-‐15° into the
periphery
...
Filled with light absorbing visual pigments (rods only have one type)
•
Inner segment: located proximally-‐ contains nucleus and biosynthetic mechanisms
•
Synaptic terminal: communicates with photoreceptor’s target cells
Phototransduction
Visual phototransduction is a process by which light is converted into electrical signals in the rod
cells, cone cells and photosensitive ganglion cells of the retina of the eye
...
3 Stages:
•
Light is absorbed by and activates pigment molecules in the photoreceptor e
...
the pigments
rhodopsin (rods) and photopsins (cones)
...
•
Reduction in [cGMP] in the cytoplasm closes ion channels, resulting in a hyperpolarizing shift
of membrane potential
•
Very complicated process: lets not get carried away with the details!
Colour Vision
•
Colour vision requires ≥ 2 types of photoreceptors with different spectral sensitivities (e
...
•
Colour vision enriches visual perception, but in itself is a poor indicator of spatial detail
•
Full colour image gives information on variations in brightness and colour
•
Colour only (purely chromatic) image: spatial detail is poor and has no information regarding
brightness (cones)
•
Black and white image (achromatic) gives good information on spatial detail and regarding
variations in brightness (rods)
Colour blindness
•
Color blindness, or color vision deficiency, is the inability or decreased ability to see color, or
perceive color differences, under normal lighting conditions
...
•
There is no actual blindness but there is a deficiency of color vision
...
This type of color
blindness is usually a sex-‐linked condition (X linked) => highest prevalence in males
•
The genes that produce photopigments are mostly carried on the X chromosome; if some
of these genes are missing or damaged, color blindness will be expressed in males with a
higher probability than in females because males only have one X chromosome (in females,
a functional gene on only one of the two X chromosomes is sufficient to yield the needed
photopigments via random X linked inactivation)
...
These people
are dichromats, and they can only match any color they see with some mixture of just two
primary colors (whereas normally humans are trichromats and require three primary colors)
...
Reduction
in information can lead to confusion and can affect their lives on a daily basis
•
This is exploited by tests for colour blindness for example, the Ishihara test
•
In principle, there can be 3 subtypes types of dichromacy due to loss of each of the 3 types
of cone
...
•
Loss of L (red) cones is termed protanopia (red protons) – X linked
•
Loss of M (green) cones is termed deuteranopia (green neuter) – X linked
•
Protanopia and deuteranopia normally occur in males, frequency ~ 1%
...
Tritanopia affects males and females with equal frequency (1 in 10,0000) as the gene is on
chromosome 7 (autosmomal, not sex linked)
...
•
Formed by the cilliary body epithelium in the posterior chamber
•
It is located in the anterior and posterior chambers of the eye, the space between the lens
and the cornea
...
•
The posterior chamber is the narrow space posterior to the peripheral part of the iris, and in
front of the suspensory ligament of the lens and the ciliary processes
•
It helps maintain the shape of the eye and its circulation transports nutrients and waste
...
•
It contains ascorbate, a powerful antioxidant
...
It is produced by an energy
dependent process in the epithelial layer of the ciliary body into the posterior chamber of
the eye
...
A small amount diffuses through
the vitreous being absorbed across the retinal pigment epithelium
...
This is called ‘open’
angle glaucoma because the angle (iridoconreal angle) is clear
...
•
The figure below shows how the world might look to a person with glaucoma
...
Charachterised by
ARCUATE SCOTOMA
...
•
The aqueous humor is also the route for nutrient transport to the avascular lens
...
•
Outcome: net movement of Cl-‐ and Na+ through the cells from interstitial fluid to aqueous
humor is accompanied by water moving through ciliary epithelial cell water channels,
aquaporins and through the paracellular pathway down the osmotic gradient created by
solute movement
•
Therefore aqueous humour flows into the posterior chamber
•
This process can be blocked by CA inhibitors (used in treatment of glaucoma)
•
Intraocular pressure is mainly determined by the coupling of the production of aqueous
humor and the drainage of aqueous humor mainly through the trabecular meshwork located
in the anterior chamber
•
The balance between secretion and drainage maintains an intracocular pressure of
approximately 17 mmHg above atmospheric
•
Intraocular pressure (IOP) is the fluid pressure inside the eye
...
IOP is an important aspect in the evaluation of
patients at risk from glaucoma
...
Normal IOP = 10-‐21 mmHg
...
•
In the set of diseases termed ‘glaucoma’, raised intra-‐ocular pressure is caused by an
imbalance between the rates of secretion and removal of aqueous humor
...
•
Strategies for treatment of this condition are directed at reducing the rate of secretion of
the aqueous humor
•
Carbonic anhydrase inhibitors will reduce production of aqueous humor and are therefore
used to reduce intra-‐ocular pressure in glaucoma
! Dorzolamide is administered as eye drops (thus avoiding systemic side effects)
! Acetazolamide is administered orally (thus also targeting kidney causing a
metabolic acidosis and a compensatory respiratory alkalosis)
...
It is often referred to as the vitreous body
or simply "the vitreous"
...
•
This can permanently damage vision in the affected eye(s) and lead to blindness if left
untreated
...
•
Increasing intra-‐occular pressure (IOP) causes displacement of the lens backwards into the
vitrous humor
...
•
The outcome is that unless treated the neuronal elements of the retina and optic nerve
sustain damage
•
Disturbances of colour vision are common as cones seem to be more susceptible to damage
compared to rods
•
Glaucoma can be roughly divided into two main categories, "open-‐angle" and "closed-‐
angle" glaucoma
...
•
Closed-‐angle glaucoma can appear suddenly (acutely) and is often painful; visual loss can
progress quickly, but the severe discomfort/red eye often leads patients to seek medical
attention before permanent damage occurs
...
Primary open angle is most common type and because there are no
conspicuous structural changes in the anterior chamber it is hard to diagnose
...
Silent theif of sight
...
INTRODUCTION TO OPTHALMOLOGY
Anatomy
Orbit of the skull
•
The orbit is the cavity or socket of the skull in which the eye and its appendages are situated
...
•
The structures entering through the superior orbital fissure are as follows:
! Cranial nerves (CN) III, IV, and VI (3,4, and 6 makes the eye do tricks)
! CN V1: lacrimal, frontal and nasociliary branches of ophthalmic (V1)
...
It
is composed of non-‐keratinized, stratified columnar epithelium with goblet cells
...
It also contributes to immune surveillance and
helps to prevent the entrance of microbes into the eye
...
The sclera
is continuous with the cornea (which sits anterior to pupil and lens)
•
Cornea: The cornea is the transparent front part of the eye that covers the iris, pupil, and
anterior chamber
...
In humans,
the refractive power of the cornea is approximately +43 dioptres
...
The curvature of the lens, on
the other hand, can be adjusted to "tune" the focus depending upon the object's distance
...
•
Uvea (iris, ciliary body, choroid -‐ ICC): The uvea is the vascular middle layer of the eye
...
It is
traditionally divided into three areas, from front to back: iris, ciliary body and choroid
...
The color of the iris is
often referred to as "eye color
...
The cornea covers the iris and pupil
...
It is coated by a double
layer, the ciliary epithelium
...
There are three sets of ciliary muscles in the eye
...
The ciliary body
receives parasympathetic innervation from the oculomotor nerve (CN III)
...
It also anchors the
lens in place
...
This causes the lens to form a more spherical shape (more convex =>
more convergent => smaller focal length) achieving a higher level of refractive
power (positive), generally improving the focus for closer objects
...
One of the essential roles of the
ciliary body is also the production of the aqueous humor, which is responsible for
providing most of the nutrients for the lens and the cornea and involved in waste
management of these areas
...
g
...
CA inhibition leads to the lowering of aqueous humor
production and causes a subsequent drop in the intraocular pressure
...
g
...
The choroid provides oxygen and nourishment to the outer layers of
the retina
...
•
Lens: The crystalline lens is a transparent, biconvex (converegent with a positive dioptre
power) structure in the eye that, along with the cornea, helps to refract light to be focused
on the retina
...
This adjustment of the lens is known as
accommodation
...
•
Retina: light-‐sensitive layer of tissue, lining the inner surface of the eye
...
Light striking the retina initiates a cascade of chemical and electrical events that ultimately
trigger nerve impulses
...
•
Aqueous humour: transparent, gelatinous fluid similar to plasma, but containing low-‐protein
concentrations
...
It is located in the anterior and posterior chambers of the eye,
the space between the lens and the cornea
...
CA is an essential
enzyme for production of aqueous humour
...
Maintains the intraocular pressure and inflates the globe of the eye
...
g
...
•
Vitreous humour: clear gel that fills the space between the lens and the retina of the eyeball
of humans and other vertebrates
...
Duplex Retina
•
A duplex retina is a retina consisting of both rod cells and cone cells
...
g
...
The vessels of the optic disc leave the
disc nasally
...
g
...
g
...
Ocular adnexae
•
Lids: An eyelid is a thin fold of skin that covers and protects the eye
...
The orbicularis oculi (CN VII) is a muscle in the face that closes the eyelids
(NOT opens)
! Ptosis (drooping of upper or lower eyelid) occurs when the muscles that raise the
eyelid (levator palpebrae superioris and superior tarsal muscles) are not strong
enough to do so properly
...
e
...
! Ptosis does NOT occur in CN VII palsy (facial nerve controls orbicularis oculi and
frontalis – not the muscles for eye lid elevation)
•
Lacrimal gland: paired almond-‐shaped glands, one for each eye, that secrete the aqueous
layer of the tear film
...
•
Lacrimal sac: The lacrimal gland produces tears which then flow into canals that lead to the
lacrimal sac
...
The optic nerve is ensheathed in all three meningeal layers (dura, arachnoid, and
pia mater) rather than the epineurium, perineurium, and endoneurium found in peripheral
nerves
...
•
Optic chiasm: location where the optic nerves (CN II) partially decussate
...
Axons cross over to transmit the contralateral visual field to the opposite side of
the brain
...
The temporal retina images (nasal visual field), on the other hand, stay on the same
side
...
•
Visual cortex (close relation to calcarine sulcus in occipital lobe)
Pupillary light reflex
•
Afferent = Retina + CN II
•
Efferent = CN III (parasympathetic)
•
Light shone in one eye elicits a pupillary light reflex that causes both the ipsilateral and the
contralateral pupil to constrict (the direct and consensual reflex, respectively)
...
Instead, a
special subset of intrinsically photosensitive ganglion cells provide the afferent limb (CN II),
with axons that distribute bilaterally in the optic chiasm and terminate in the pretectal area
(midbrain)
...
•
Because light in either eye causes both the ipsilateral and the contralateral pupil to constrict
(direct and consensual reflexes, respectively), both pupils ordinarily will be pretty much the
same size under any given condition of illumination; if they are not (anisocoria), there likely
is a problem with the autonomic innervation or with the iris itself
...
•
CN IV Trochlear: innervates superior oblique muscle (SO4): intorsion and depression on
adduction
•
CN V Trigeminal:
! CN V1 (ophthalmic): Sensory innervation to the cornea, ciliary body, and iris; to
the lacrimal gland and conjunctiva; and to the skin of the upper eyelids, and
eyebrow
...
Stimulation should elicit both a direct and consensual response (response of the opposite eye)
...
1 second
...
The reflex is mediated by:
•
Afferent: ophthalmic branch (CN V1) of CN V (trigeminal nerve) sensing the stimulus on the
cornea, lid, or conjunctiva (avoid touching the cornea!)
•
Efferent: CN VII (Facial nerve) initiating the motor response (blinking) e
...
contraction of
obicularis occuli
Refractive Errors
•
Emmetropia: normal eyes with no refractive error
•
Hypermetropia or hyperopia (long sightedness with short eye): defect of vision caused by an
imperfection in the eye (often when the eyeball is too short or the lens cannot become
convex enough), causing difficulty focusing on near objects, and the image forming behind
the retina
...
•
Myopia (shortsightedness -‐ what I have – with long eye): condition of the eye where the light
that comes in does not directly focus on the retina but in front of it (often because eye is too
long or lens is too convex), causing the image that one sees when looking at a distant object
to be out of focus, but in focus when looking at a close object
...
•
Astigmatism: optical defect in which vision is blurred due to the inability of the optics of the
eye to focus a point object into a sharp focused image on the retina
...
Corrected with toric lens
...
The
ability to focus on near objects declines throughout life, from an accommodation of about
20 dioptres (ability to focus at 50 mm away) in a child, to 10 dioptres at age 25 (100 mm),
and levels off at 0
...
Corrected with convex (positive dioptre lens) e
...
reading glasses
...
g
...
Eye diseases such as cataracts,
macular degeneration and uveitis can cause glare
...
People with this
condition often first notice this when looking at mini-‐blinds in their home
...
g
...
Can occur as a result of several different medical conditions,
related to the eye or the nervous system including migraine headaches, cataracts, mild
traumatic brain injury (MTBI), meningitis, SAH, or severe ophthalmologic diseases such as
uveitis or corneal abrasion
...
•
Floaters: Floaters are deposits of various size, shape, consistency, refractive index, and
motility within the eye’s vitreous humour, which is normally transparent
...
At a
young age, the vitreous is transparent, but as one ages, imperfections gradually develop
...
Often associated with VH or RD
...
A more common cause of flashing lights is migraine
...
•
Oscillopsia: visual disturbance in which objects in the visual field appear to oscillate
...
Oscillopsia is an incapacitating condition experienced by many patients with neurological
disorders
...
A change in the size of the
vestibulo-‐ocular reflex due to vestibular disease can also lead to oscillopsia during rapid
head movements
...
e
...
It is usually the
result of impaired function of the extraocular muscles (EOMs), where both eyes are still
functional but they cannot converge to target the desired object
...
g
...
Diplopia is often one
of the first signs of a systemic disease, particularly to a muscular (myasthenia gravis or
thryroid eye disease) or neurological process (MS, INO, cerebellar disease or CN
dysfunction), and it may disrupt a person’s balance, movement, and/or reading abilities
...
g
...
•
Pain: can be localised or referred, perform SOCRATES
•
Discomfort / dryness / foreign body sensation
•
Abnormal appearance (red/swollen)
•
Itch
•
Discharge / watering / epiphora (overflow of tears onto the face)
General Medical History
•
Relevant systematic enquiry
•
Past medical history (e
...
DM, thyroid disease, HT, etc)
•
Past ophthalmic history
•
Family history (e
...
glaucoma, squint, thyroid disease)
•
Drug history and allergies
•
Social history: pets, travel history may be relevant, DRIVING, CONTACT HISTORY
•
Occupational history
Ophthalmic Examination
•
Work from anterior to deep
•
Facial appearance
•
Lids, lashes and lacrimal system (LLL)
•
Conjunctiva -‐ where is the redness?
•
Cornea: corneal reflex, opacity, fluorescein eye drops
•
Pupils: symmetry, shape, size, reflexes
•
Iris
•
Lens
•
Red reflex: reddish-‐orange reflection of light from the eye's retina that is observed when
using an ophthalmoscope or retinoscope from approximately 30 cm
...
Many eye problems may be detected by this
test, such as: cataracts (show leukocoria, an abnormal white reflection from the retina of
the eye) or retinoblastoma (shows leukocoria)
...
RD and VH can also cause dimished red reflex
...
•
Medical signs that can be detected from observation of eye fundus (generally by
funduscopy) include optic disc pathology, hemorrhages, exudates, cotton wool spots, blood
vessel abnormalities (tortuosity, pulsation and new vessels) and pigmentation
...
Examination: equipment
•
Acuity chart (Snellen chart) +/-‐ Ishihara colour perception tests
•
Pen torch
•
Magnifying aid
•
Ophthalmoscope
•
Eye drops for examination
! Fluorescein (orange liquid): Fluorescein sodium eyedrops is used extensively as a
diagnostic tool in the field of ophthalmology and optometry
...
It will temporarily stain any cells it enters
and therefore marks any damaged areas of the eye
...
Remember that the cornea is continuous with
the sclera
...
! Anaesthetic drops – particulary useful for removing foreign body
! Mydriatic drops: topical eye drops (e
...
tropicamide, cyclopentolate, atropine,
phenylephrine) which cause mydriasis (dilation of the pupil)
...
Purposely-‐induced mydriasis
via mydriatics is also used as a diagnostic test for Horner's Syndrome
...
g
...
Remember that the distance of measurement (usually 6 metres) is recorded
on the numerator
...
With
glasses, without glasses, with hat pin
...
Blindness = 3/60
...
•
Colour vision (Ishihara test)
•
Visual fields (by examination or with machine) including testing for visual neglect
•
Blind spot (with hat pin and small red and white object)
OCULAR TRAUMA
Ophthalmic Casualties
Physical or chemical injuries of the eye can be a serious threat to vision if not treated appropriately
and in a timely fashion
...
This
is not, however, universally true, as tiny metallic projectiles may cause neither symptom
...
Intraocular foreign bodies (IOFBs) do not cause pain because of the lack of nerve endings in the
vitreous humour and retina that can transmit pain sensations
...
Ideally, ointment would not be used when referring to an ophthalmologist,
since it diminishes the ability to carry out a thorough eye examination
...
g
...
•
Work related (often minor)
•
Household related e
...
DIY (hammering metal on metal)
•
Assault (blunt trauma in a fist fight)
•
Accidents around the home
•
Sports associated eye injury: Sporting balls such as cricket ball, lawn tennis ball, squash ball),
shuttle cock (from Badminton) and other high speed flying objects can strike the eye
•
Road traffic accidents (RTAs) with head and facial trauma may also have an eye injury -‐ these
are usually severe in nature with multiple lacerations, shards of glasses embedded in tissues,
orbital fractures, severe hematoma and penetrating open globe injuries with prolapse of eye
contents
...
Immediately irrigate
...
It
is used as a screening test for many corneal disorders including corneal post-‐trauma, corneal
perforation and corneal degeneration
...
At this point,
the fluorescein appears green in color
...
If the fluorescein strip turns pale upon
application to the corneal surface, the person tests positive for the corneal deformity he/
she is being tested for
...
•
Use fluorescein drops to identify area of epithelial loss – do this after Seidel test
•
Anaesthetic drops may be required
•
CN exam
Blunt trauma
Blowout fracture
•
Blowout fracture of the orbit is caused by blunt trauma, classically described for fist or ball
injury, leading to fracture of the floor or medial wall of the orbit due to sudden increased
pressure on the orbital contents
...
•
When an external force is applied to the orbital cavity from an object whose diameter is
larger than that of the orbit, the orbital contents are retropulsed and compressed
...
)
•
Motor vehicle accidents
•
Facial trauma
Traumatic uveitis
•
Uveitis is, broadly, inflammation of the uvea
...
Uveitis requires
an urgent referral and thorough examination by an ophthalmologist and urgent treatment to
control the inflammation
...
•
Anterior uveitis refers to an inflammation of the iris and ciliary body
...
•
Uveitis can be sight threatening => opthalmological emeregency
Clinical features of uveitis include:
•
Painful red eye: the pain can range from mild aching to intense discomfort, and reading or
other tasks that require you to focus your eye can make the pain worse blurred or cloudy
vision
•
Constricted pupil with cilliary spasm – contributes to pain (cycloplegics such as
cyclopentolate can help)
•
Redness (injection) is centred around the cornea => circumcorneal injection (ciliary flush)
...
The redness is also more
profound in uveitis
•
Loss of peripheral vision: the ability to see objects at the side of your field of vision
•
Seeing flashing lights (flashers)
•
Corneal haze and distortion
•
Sensitivity to light (photophobia)
•
Floaters: shadows that move across the field of vision
•
Iris synechiae (pupil distortion): sign of uveitis
•
Anterior chamber flare (inflammatory cells floating around the anterior chamber)
•
Hypopyon (if severe): seen as yellowish exudate in lower anterior chamber of eye
...
Hypopyon
•
Hypopyon = inflammatory cells in the anterior chamber of eye (cellular flare which have
settled down at bottom of chamber)
•
It is a leukocytic exudate, seen in the anterior chamber, usually accompanied by redness of
the conjunctiva and the underlying episclera
...
e
...
The exudate settles at the bottom due
to gravity
...
It may appear as a reddish
tinge, or it may appear as a small pool of blood at the bottom of the iris or in the cornea
•
Hyphemas are frequently caused by injury, and may partially or completely block vision
...
Other complications of blunt trauma
•
Tearing of intra-‐ocular structures
•
Blow out fracture of orbit
•
Dislocated lens (ectopia lentis)
•
Retinal detachment
•
Choroidal tear
•
Optic nerve avulsion
Penetrating trauma (large objects)
•
Lid laceration
•
Corneal laceration
•
Scleral laceration
•
Sympathetic ophthalmia
Sympathetic ophthalmia
•
Sympathetic ophthalmia (SO) is a bilateral diffuse granulomatous uveitis (a kind of
inflammation) of both eyes following trauma to one eye
...
•
Symptoms may develop from days to several years after a penetrating eye injury
...
•
The immune system, which normally is not exposed to ocular antigens, is introduced to the
contents of the eye following traumatic injury
...
The onset of this process can be from days to years
after the inciting traumatic event
•
A penetrating injury to one eye can result in exposure of intra-‐ocular antigens to the
immune system resulting in an immune response and generation of auto antibodies which
will attack both eyes
...
•
The disease may progress to severe uveitis with pain and photophobia
...
•
The retina, however, usually remains uninvolved, although perivascular cuffing of the retinal
vessels with inflammatory cells may occur
...
A hollow
structure, the bulbus oculi is composed of a wall enclosing a cavity filled with fluid with three
coats: the Sclera, Choroid, and the Retina
...
Its
anterior surface, transparent and more curved, is known as the cornea of the bulbus oculi
...
•
IOFB can be caused by fast moving particles e
...
hammer and chisel injuries
•
Don’t apply pressure to eye in suspected IOFB => risk of rupture
•
Always X-‐ray potential IOFBs (good history)
•
GOOD HISTORY CAN HELP DECIDE LIKLEYHOOD OF IOFB
CT scan is best
Chemical burns
Alkali:
•
Easy, rapid penetration
•
Cicatrising (scarring) changes to conjunctiva and cornea
•
Penetrates the intra-‐ocular structures
Acid:
•
Coagulates proteins
•
Little penetration
Assessment of chemical injury
•
Assessment of chemical injury occurs AFTER thorough irrigation
•
Washout chemical burns immediately – take history after
Physical burns
•
Thermal or heat burns of the eye can occur in the workplace when sparks fly from welding
equipment or when hot industrial materials such as molten plastics, metals, or hot gases
accidentally penetrate the eye
...
•
Thermal burns are generally mild, as exposure to extreme heat sources stimulates the blink
reflex (corneal reflex), allowing the eyelids to protect the eye surface
...
g training, safety, up-‐to-‐date machinery
•
Protective eye wear
•
Clear rules: sport and work
•
Education: to ensure awareness
NEUROLOGICAL CONDITIONS AND THE EYE
•
•
Neuro-‐ophthalmology is the subspecialty of both neurology and ophthalmology concerning
visual problems that are related to the nervous system
...
Cardinal Features of neuro-‐ophthalmic disease
•
Eye movement defects:
! Nystagmus (involuntary eye movements e
...
tremor of extra-‐ocular muscles =>
tremor of eye)
! Diplopia (double vision) – if binocular suggests neurological (including muscular)
disorder, however if monocular suggests eye pathology (e
...
cataracts)
•
Visual defects:
! Diminished visual acuity (VA)
! Visual field loss
! Visual neglect
Aetiology
Aetiology depends on age, other clinical findings and site of lesion
•
•
Inflammation/infection
•
Demyelination (e
...
MS)
•
Tumours (primary and secondary) act as SOLs
•
Other SOLs e
...
abscess or haemorrhage
•
Trauma
•
Vascular disease
Congenital abnormalities
Identify cause
•
Full medical and neurological examination
•
Full eye examination
•
Blood tests
•
Imaging: MRI scanning (secondary prevention of vascular disease is important to reduce
further morbidity)
Ocular Motility Defects
•
CN III (Oculomotor) palsy: “down and out” – exotropia and hypotropia, ptosis (levator
palpabrae dysfunction), and mydriasis (pupil dilation) if compressive lesion
•
CN IV (Trochlear) palsy of SO muscle: hypertropia – due to unopposed IO, head tilt away
from affected side
•
CN VI (Abducent) palsy of LR muscle: failure to abduct (resulting in esotropia), head tilt to
affected side
•
Inter-‐nuclear opthalmoplegia: Injury or dysfunction to the medial longitudinal fasciculus
(MLF), a heavily-‐myelinated tract that allows conjugate eye movement (coordination
between right and left eye movements) by connecting the paramedian pontine reticular
formation (PPRF) -‐ abducens nucleus complex of the contralateral side to the oculomotor
nucleus of the ipsilateral side
...
When an attempt is made to gaze
contralaterally (relative to the affected MLF and eye), the affected eye adducts minimally, if
at all
...
The divergence of the eyes
leads to horizontal diplopia
...
In older patients with one-‐sided lesions a stroke is a distinct possibility
...
•
Supra-‐nuclear opthalmoplegia: Progressive supranuclear palsy (PSP) is a neurodegenerative
disease of the brain involving the gradual deterioration and death of specific volumes of the
brain
...
CN VI nerve palsy
•
Sixth nerve palsy (abducent nerve palsy) is a disorder associated with dysfunction of cranial
nerve VI (the abducent nerve), which is responsible for contracting the lateral rectus muscle
to abduct the eye
...
•
Strabismus (squint) is a condition in which the eyes are not properly aligned with each other
...
It thus hampers proper binocular
vision, and which may adversely affect depth perception, and cause diplopia
•
Esotropia is a form of strabismus, or "squint", in which one or both eyes turns inward e
...
a
convergent squint on distance fixation
...
•
The condition can be constantly present, or occur intermittently, and can give the affected
individual a "cross-‐eyed" appearance
•
The striabmus and esotropia can result in horizontal diplopia (double vision)
•
Diplopia is typically experienced by adults with CN VI nerve palsies, but children with the
condition may not experience diplopia due to suppression
...
•
Because the abducent nerve emerges near the bottom of the brain, it is often the first
nerve compressed when there is any rise in intracranial pressure
...
•
Rememeber CN VI originates from pons
Diagnosis:
•
Most cases of sixth nerve palsy seen in the examination have an obvious manifest esotropia
(convergent squint (“cross eye”) seen without performing cover-‐uncover test e
...
manifest)
on distant fixation making the diagnosis easy
...
The affected eye has a convergent squint (this may not be obvious in
mild or partially recovered sixth nerve palsy)
...
•
On ocular motility testing:
! The affected eye has limited abduction
...
g
...
•
We assess CV risk factors, as vascular pathology is the commonest cause in older
individuals (e
...
mononeuritis multiplex)
•
DM and mononeuritis multiplex is the commonest cause
Causes
•
Microvascular (DM, HT, atherosclerosis, embolism) – mononeuritis multiplex => ASSESS CV
RISK FACTORS
•
Raised Intracranial pressure (trauma, SOL, tumour etc) – must rule this out (e
...
ask about
headaches, neuroligical symptoms, check for pappiloedema, neuro exam)
•
MS
•
Congenital
Pappiloedema
•
Papilledema (or papilloedema) is optic disc swelling secondary to increased intracranial
pressure
...
Unilateral presentation is extremely rare
...
•
Assess for papilloedema in all patients with EOM dysfunction
•
NB: The optic disc or optic nerve head is the location where ganglion cell axons exit the eye
to form the optic nerve
...
This causes a break in the visual field called "the blind spot" or the
"physiological blind spot"
...
The optic disc is
also the entry point for the major blood vessels that supply the retina
...
! Loss of venous pulsation can also occur
! Hemorrhages over and / or adjacent to the optic disc
! Papilledema (optic disc swelling secondary to raised intracranial pressure) is
almost always bilateral
...
•
Palsy (or plegia) refers to a complete weakness (paralysis) of a muscle while a paresis is a
partial weakness
...
•
The superior oblique muscle is important for intorsion, depression (in adduction) and
abduction (weak)
•
The depressing action of superior oblique is most effective when the eye is in an adducted
position
...
The main muscle for abduction is the lateral rectus,
so although superior oblique contributes to a downwards and lateral eye movement, testing
this motion would not be specific enough as inferior and lateral recti muscles would also be
tested
...
This is a source of confusion on the subject as although
clinical testing asks the patient to adduct and depress the eye, anatomically the muscle
depresses and abducts it
•
Test the SO by depression on adduction
•
Weakness of the superior oblique muscle causes a combination of vertical, horizontal and
torsional misalignment of the eyes (due to its complicated mechanism of action) => vertical,
horizontal and torsional diplopia
•
The torsional phenomenon occurs more frequently with acquired cases of superior oblique
palsy
...
•
Superior oblique palsy may cause double vision (diplopia) because of
misalignment/strabismus of the eyes (the brain perceives an image from two different
directions)
...
•
Head tilt and/or turn is common with superior oblique palsy (usually to unaffected side)
which is in contrast to CN VI palsy where the head is turned to the effected side
...
•
A child with a head tilt should be evaluated by an ophthalmologist for superior oblique
palsy and other possible eye problems
...
The
trochlear nucleus is unique in that its axons run dorsally and cross the midline (decussate)
before emerging from the brainstem
...
Lesions of all other cranial nuclei affect the ipsilateral side (as
decussation occurs before cerebral cortex fibres reach CN nuclei) except the optic nerves
which innervate both eyes
...
Alternatively, the patient may be wearing glasses with prism
...
Patients with superior oblique
palsy on one side experience double vision, which is improved or even abolished by tilting
the head towards the shoulder on the unaffected side
...
•
Hypertropia: condition of misalignment of the eyes (manifest strabismus), whereby the
visual axis of one eye is higher than the fellow fixating eye (“up and in”) – occurs due to
unopposed action of IO
•
Head tilt: usually to unaffected side but may paradocially tilt to affected side
Diplopia (often vertical) – on adduction (e
...
when going down the stairs and our eyes are
adducted)
Bilateral CN IV palsy
Clinical features:
•
Torsion
•
Chin depressed
Cause:
•
Blunt head trauma
Aetiology of CN IV palsy
•
Congenital (decompensated): when present at birth, it is known as congenital fourth nerve
palsy
•
Microvascular: DM, HT, hyperlipidaemia – often mononeuritis multiplex secondary to DM
...
CN III palsy
•
Oculomotor nerve palsy is an eye condition resulting from damage to the third cranial nerve
or a branch thereof
...
The limitations of eye movements resulting from the condition are
generally so severe that the affected individual is unable to maintain normal alignment of
their eyes when looking straight ahead, leading to manifest strabismus and, as a
consequence, double vision (diplopia)
...
The eye will be displaced
outward (abducted) and displaced downward (depressed); outward because the lateral
rectus (innervated by the sixth cranial nerve) maintains muscle tone in comparison to the
paralyzed medial rectus
...
•
The affected individual may also present with:
! Ptosis (drooping of the eyelid) due to levator palpabrae superioris dysfunction
! Mydriasis (pupil dilation) due to decreased parasympathetic innervations to
sphincter pupillae – blown out pupil (ONLY IF COMPRESSIVE LESION)
•
Compressive oculomotor nerve damage could result in compression of the parasympathetic
fibers before any disruption of the motor fibers occurs, since the parasympathetic fibers run
on the outside of the nerve
...
•
Pupil involvement => suggestive compression => surgical CN III palsy (often due to
posterior communicating aneurysm or midbrain lesion)
•
If pupil not involved => medical CN III palsy (often due to mononeuritis multiplex
secondary to DM)
Diagnoisis:
•
In complete third nerve palsy, the patient will have complete ptosis
...
g
...
g
...
If pupil involved => urgent MRI
...
The superior oblique muscle is
innervated by cranial nerve IV (trochlear nerve)
•
Incyclotorsion may also be used to describe one part of the condition of the eye when a
patient has an oculomotor nerve palsy
...
e
...
This occurs due to loss
of IO which excylotorts
...
It is a physical
finding in certain neurologic illnesses
...
This involves the inter-‐nuclear
pathways such as the medial longitudinal fasciculus (MLF)
...
•
Internuclear ophthalmoplegia (INO) is a specific gaze abnormality characterized by impaired
horizontal eye movement (conjugate lateral gaze) with weak adduction of the affected eye
and abduction nystagmus of the contralateral eye
...
•
We also get nystagmus of the contralateral eye on abduction
Medial longitudinal fasciculus (MLF)
•
The medial longitudinal fasciculus (MLF) is a pair of crossed fiber tracts (group of axons), one
on each side of the brainstem
...
•
The medial longitudinal fasciculus carries information about the direction that the eyes
should move
...
•
It is an integral component of saccadic eye movements, visual tracking as well as vestibulo-‐
ocular and optokinetic reflexes
...
•
Lesions of the MLF produce internuclear ophthalmoplegia (INO) and can be a presenting
symptom of multiple sclerosis, where it presents as nystagmus and diplopia (often
bilateral INO)
•
Stoke can cause unilateral INO
Causes of inter-‐nuclear ophthalmoplegia
•
Multiple sclerosis (particularly if bilateral and younger patient)
•
Vascular (particularly if unilateral and older patient)
Defects in visual field
Depends on location of lesion:
•
Retina
•
Optic nerve
•
Chiasm
•
Optic tracts
•
LGN of thalamus
•
Optic radiations
•
Cortex
Aetiology
•
Vascular disease e
...
stroke, TIA, haemorrhage
•
Space occupying lesion (SOL)
•
Demyelination (MS)
•
Trauma (including surgical)
•
Commonest aetiology of any defect depends on age, other clinical findings and site of lesion
Clinical presentation
Optic nerve
•
Ischaemic optic neuropathy: many causes, arteritic or non arteritic
•
Optic neuritis (commonly caused by MS): central scotoma, painful eye movements, loss of
red vision (red desaturation), RAPD
•
Tumours (rare)
! Meningioma
! Glioma
! Haemangioma
•
Optic nerve defects are complete (complete loss of pupil reflexes) or abide the horizontal
(altitudinal hemianopia due to blood supply to optic nerve head) or produce a cental
scotoma of the visual field of the affected eye (due to enlarged blind spot)
...
Optic neuritis
•
Optic neuritis is a multi-‐aetiological condition consisting in the inflammation of the optic
nerve that may cause a complete or partial loss of vision in the affected eye
...
Direct axonal damage may also
play a role in nerve destruction in many cases
...
Up to 50% of patients with MS will
develop an episode of optic neuritis, and 20-‐30% of the time optic neuritis is the presenting
sign of MS
...
g
...
g
...
g
...
Clinical features:
•
Progressive visual loss (unilateral)
•
Optic nerve defects are complete or abide the horizontal (altitudinal hemianopia) or
produce a central scotoma of the visual field of the affected eye
•
Central scotoma: central scotoma is an area of depressed vision that corresponds with the
point of fixation and interferes with central vision
...
g
...
g
...
03%
!
Drug used to lower IOP in glaucoma (prostaglandin analogue) – often first line (for open
angle glaucoma; PG analogues and beta blocker are first line for open angle)
!
Increase uveroscleral outlfow
!
Benzalkonium concentration=0
...
01%
•
Drug used to lower IOP in glaucoma (prostaglandin analogue) – often first line
•
Benzalkonium concentration=0
...
Treatment of Infections
Three broad categories -‐ all act on bacteria and either:
•
Inhibit protein synthesis (act on ribosomes)
•
Inhibit cell wall synthesis
•
Inhibit nucleic acid (DNA/RNA) synthesis
Chloramphenicol
•
Chloramphenicol is the most commonly used topical antibiotic
•
Ointment or drops
•
Inhibits peptidyl transferase enzyme (therefore stops bacterial protein being made)
Side effects:
!
Allergy
!
Irreversible aplastic anaemia (rare : 1 in 40,000) – can cause pancytopenia
!
Grey baby syndrome
NOT USED IN CL WEARERS (often no activity agaianst Pseudomonas aurginosa)
Antibiotics that inhibit nucleic acid synthesis
!
Quinolones e
...
ofloxacin, inhibit DNA gyrase, an enzyme that compresses bacterial DNA
into supercoils
...
!
Inhibition of DNA gyrase leads to unwinding of supercoils and cell death (bactericidial)
Antibiotics that inhibit cell wall synthesis
!
Penicillins & cephalosporins have common beta lactam ring
!
Beta lactam ring inhibits enzyme which makes bacterial cell wall
!
Without cell wall, bacteria die (bactericidal)
Antivirals
Zovirax
!
Zovirax (acyclovir) inhibits viral DNA synthesis
!
Base analogue (mimics guanine)
!
Used for dendritic ulcers of the cornea (e
...
as a result of herpes simplex or herpes zoster)
...
g
...
g
...
g
...
g
...
g
...
g
...
g
...
g
...
When the ciliary muscle contracts, it
opens the trabecular meshwork, which facilitates the rate that aqueous humor drainage =>
the intraocular pressure decreases; pilocarpine also acts on iris muscle to cause pupil
constriction (miosis) which helps to open up the angle
...
•
Alpha 2 adrenergic agonist: Brimonidine (‘Alphagan’)
...
g
...
It is a possible complication of all intraocular surgeries, particularly
cataract surgery, with possible loss of vision and the eye itself
...
Other causes include penetrating trauma and retained
intraocular foreign bodies
...
Corneal abrasion (damage shows up green on illumination with blue light)
•
2
...
Diagnosing nasolacrimal duct obstruction
•
4
...
g
...
g
...
g phenylephrine
•
Phenylephrine can be used to distinguish betwee scleritis (does not blanch) and episcleritis
(does blach)
Steroids cause cataract
•
A cataract is a clouding of the lens inside the eye which leads to a decrease in vision
...
•
Visual loss occurs because opacification of the lens obstructs light from passing and being
focused on to the retina at the back of the eye
...
Over time, yellow-‐brown pigment is
deposited within the lens and this, together with disruption of the normal architecture of
the lens fibers, leads to reduced transmission of light, which in turn leads to visual problems
...
•
Corticosteroids (and other drugs) can induce cataract development
Ethambutol can cause optic neuropathy
•
Ethambutol (TB drug) can cause optic neuropathy
•
Optic neuropathy refers to damage to the optic nerve due to any cause
...
•
The main symptom is loss of vision, with colors appearing subtly washed out in the affected
eye
...
A
pale disc (pallor of the disc) is characteristic of long-‐standing optic neuropathy
...
Optic neuropathy
Optic neuropathy may be caused by any of the following:
•
Ischemic optic neuropathy (insufficient blood flow (ischemia) to the optic nerve) e
...
temporal arteritis
•
Optic neuritis (indicative of MS)
•
Compressive optic neuropathy (tumors, infections, and inflammatory processes can cause
lesions within the orbit and, less commonly, the optic canal
...
g
...
g
...
VISUAL LOSS AND BLINDNESS
VISUAL LOSS
•
Sudden loss of vision
•
Transient loss of vision
•
Gradual loss of vision
Causes of sudden visual loss
Use the mnemonic ‘VARICOSE’:
•
Vascular occlusion and vitreous haemorrhage
•
Age related macular degeneration (wet type)
•
Retinal detachment (RD)
•
Ischaemic optic neuropathy – arteritic and non-‐arteritic
•
Closed angle glaucoma (ACAG)
•
Optic neuritis
•
Stroke
•
Emergency referral
Central retinal artery occlusion (CRAO)
•
•
Central retinal artery occlusion (CRAO) is a disease of the eye where the flow of blood
through the central retinal artery is blocked (occluded)
...
CRAO is an ocular analogue of cerebral stroke
...
g
...
The affected eye will appear to dilate
when the light is swung to it
...
A RAPD (also known as Marcus
Gunn Pupil) is distinguished from a total CN II lesion, in which the affected eye perceives
no light
...
•
Pale retina (pallor) due to lack of blood flow -‐ milky retina
•
Thread-‐like retinal vessels due to lack of blood flow
•
Cherry red spot (we can see normal choroidal circulation (deep to retina) at fovea where
the retina is thinnest due to lack of blood flow)
Causes of CRAO
•
Carotid artery disease e
...
•
Establish source of embolus: carotid doppler (e
...
to check for carotid atheroma) and ECG
(e
...
to check for AF)
•
Assess and manage risk factors (e
...
hyperlipidaemia, DM, smoking and HT)
Types of retinal artery occlusion
•
Central renal artery occlusion (CRAO): most severe and more common (profound, sudden,
painless los of vision)
•
Branch retinal artery occlusion (BRAO): less severe and rare -‐ Remember that due to lens
inversion a superior lesion of the retina will result in inferior visual field loss
...
g
...
It is a
common clinical symptom indicative of transient retinal ischaemia, usually associated with
stenosis of the ipsilateral carotid artery or emboli (cardiac and aortic)
...
These symptoms
are often produced by atherosclerotic stenosis of the carotid vessels at the ipsilateral carotid
bifurcation and emboli from these areas causing focal, repetitive, retinal ischaemia
Causes:
•
Carotid vessel atherosclerosis => perform carotid doppler
•
Cardiac emboli => perform ECG
•
Giant cell arteritis – assess ESR => NOT ONE TO BE MISSED
•
SLE
•
Polycythaemia (hyperviscosity)
•
Other causes of hyperviscotiy e
...
myeloma
•
Full bloods required
In younger pts consider hyperviscoity of blood and Ix accordingly
Symptoms:
•
Transient painless visual loss: ‘like a curtain coming down’
•
Other descriptions of this experience include a monocular blindness with dimming, fogging,
or blurring
•
Lasts approximately 5 mins with full recovery
Signs
•
Usually nothing abnormal to see on examination
•
May identify AF (irregularly irregular pulse)
Management:
•
Amaurosis fugax may be a sign of an impending TIA or stroke and therefore patient should
be immediately referred to TIA/stroke clinic
•
Carrotid Doppler
•
ECG
•
Identify and manage CV risk factors
•
Full set of bloods to look for signs of hypercoagulability and hyperviscosity – esp if young
•
Coagulation screen?
•
Aspirin? Yes!
Migraine
•
Migraine is another cause of sudden transient visual loss
•
Visual loss may be part of the aura which precedes the migraine
•
Visual loss is usually followed by a migraine headache (however migrains can be acpehalic =>
no pain)
•
Migraine auras can present with near enough any neurological symptom => always have
migraine in the DD!
•
DON’T FORGET! MUST ask about headache, although rememeber that migraine can occur
without headache
...
•
When the central retinal vein is blocked, the circulation through the retina is greatly
reduced
...
When this happens, the retina doesn’t function
well, and the vision becomes blurred
...
It is more
common in patients with glaucoma, high blood pressure, arteriosclerosis, and diabetes than it is in
other people
...
g
...
g
...
•
Moderate to severe visual loss
Signs:
•
Pizza fundus
•
Dilated tortuous veins (can rupture and haemorrhage) due to blockage and build up of
pressure
•
Retinal haemorrhages
•
Optic disc swelling
•
Macula oedema
•
+/-‐ Neovascularisation (formation of functional microvascular networks with red blood cell
perfusion)
CRVO: treatment
•
Based on treatment of systemic or ocular causes (e
...
hypertension, DM, glaucoma)
•
Monitor: may develop new vessels (neovascularisation) and laser treatment may be required
to avoid complications e
...
vitreous haemorrhage from the new vessel
Branch retinal vein occlusion (BRVO)
•
Branch retinal vein occlusion (BRVO) is a common retinal vascular disease of the elderly
...
•
BRVO is 3 times more common than CRVO (in contrast to CRAO which is much more
common than BRAO)
•
Usual age of onset is 60-‐70 years
...
•
This usually results in blurred vision, or a missing area of vision (scotoma)
...
Remember that due to lens inversion a superior lesion of the retina will result
in inferior visual field loss and vice versa
...
A blockage to the central or main
retinal vein is more serious, and usually involves a more severe loss of vision
...
Clinical features:
•
Sudden onset of blurred vision or a visual field defect
•
Segmental haemorrhages and torturous veins
•
The quadrant affected will determine the visual field defect e
...
superior temporal
quadrant haemorrhage will result in inferior visual field defect of the nasal fields
•
The eye examination findings of acute BRVO include superficial hemorrhages, retinal edema,
and often cotton-‐wool spots in a sector of retina drained by the affected vein
...
•
The vitreous humor is the clear gel that fills the space between the posterior aspect of the
lens and the retina of the eye
...
Abnormal blood vessels can
form in the back of the eye in a person with diabetes (neovascularisation)
...
•
Other causes include trauma, retina tears, age-‐related macular degeneration, and, retinal
neovascularization as a result of branch or central retinal vein occlusion
Symptoms
•
Sudden Loss of vision
•
Blurry vision
•
Floaters and flashers
•
Photopsia: brief flashes of light in the peripheral vision
•
Note: often resolves itself with time, in contrast to retinal detachment where visual loss will
persist
Signs
•
May have loss of red reflex (e
...
loss of reddish-‐orange reflection of light from the eye's
retina that is observed when using an ophthalmoscope or retinoscope from approximately
30cm) due to opaqueness of vitreous
•
VH observable
Management:
•
•
Monitoring – many will resolve
•
Identify cause (e
...
new vessels in diabetic retinopathy or after vein occlusion)
Vitrectomy for non-‐resolving cases
ARMD wet type (age related macular degeneration: wet type)
•
Neovascular or exudative ARMD, the "wet" form of advanced AMD, causes vision loss due
to abnormal blood vessel growth (choroidal neovascularization) ultimately leading to blood
and protein leakage (“wet”) below the macula
...
•
Cause of rapid vision loss (unlike dry ARMD)
•
Only about 10% of patients suffering from macular degeneration have the wet type
...
Symptoms
•
Rapid visual loss
•
Central scotoma: Loss of vision in the center of the visual field because of damage to the
macula region of the retina
...
Stops new blood vessels growing by binding to VEGF
(vascular endothelial growth factor)
Retinal Detachment
•
Retinal detachment is a disorder of the eye in which the retina peels away from its
underlying layer of support tissue
...
•
Can occur in DM due to scarring – tractional RD
•
It is a medical emergency
...
There are two types:
•
Arteritic (50%): due to temporal arteritis (also called giant cell arteritis), an inflammatory
disease of medium-‐sized blood vessels
...
•
Non-‐arteritic (50%): atherosclerosis, idiopathic
Clinical features:
•
Both cause sudden, profound visual loss
•
Swollen pale disc – optic disc swelling
Arteritic AION pathogenesis
•
•
Visual loss occurs due to ischaemia of optic nerve head (posterior ciliary arteries blocked)
•
Medium to large sized arteries become inflamed (multinucleate giant cells)
•
Arteritic AION occurs due to giant cell arteritis (GCA)
NB: The posterior ciliary arteries supply the anterior part of the optic nerve (optic nerve
head)
Giant cell arteritis (temporal arteritis)
•
Giant-‐cell arteritis GCA (or temporal arteritis) an inflammatory vascular disease of blood
vessels most commonly involving large and medium arteries of the head, predominantly the
branches of the external carotid artery (however can affect variety of arteries in different
locations)
...
The name (giant cell arteritis) reflects the type of
inflammatory cell involved as seen on a biopsy
...
•
May cause sudden irreversible blindness
•
Giant cell arteritis is the prime medical emergency in ophthalmology because of its dreaded
complication of permanent visual loss in one or both eyes, which is preventable if these
patients are diagnosed early and treated immediately and aggressively with systemic
corticosteroids
•
Diagnosis can be difficult as patient may or may not have typical features
Symptoms:
•
Headache (usually temporal)
•
Jaw claudication
•
Scalp tenderness (painful to comb hair)
•
Tender/enlarged scalp arteries
•
Amaurosis fugax (transient loss of vision in one eye due to a temporary lack of blood flow to
the retina)
•
Malaise
•
May be comorbid with Polymyalgia rheumatica (stiff, painful muscles, particularly
shoulder muscles, absence of weakness, normal CK, raised PV/CRP/ESR)
Signs:
•
Pale, swollen disc (key sign of ischaemic optic neuropathy)
! Swollen optic disc: can occur due to an inflammatory occlusion of the ciliary
feeder vessels (posterior ciliary artery) of the optic nerve, a common finding in
giant cell arteritis
...
g
...
g
...
g
...
g
...
•
It is oe of the most common cause of blindness and is conventionally treated with surgery
...
•
Catarct can be seen as a clouding of the lens (seen looking through the cornea, pupil and iris)
•
Visual loss occurs because opacification of the lens obstructs light from passing and being
focused on to the retina at the back of the eye
...
g
...
Over time, yellow-‐brown
pigment is deposited within the lens and this, together with disruption of the normal
architecture of the lens fibers, leads to reduced transmission of light, which in turn leads to
visual problems
...
Aetiology
•
Age related (lens is a permenanet structure which does not regenerate)
•
Congenital: intrauterine infection e
...
rubella (importance of checking red reflex in
neonates)
•
Traumatic
•
Metabolic: DM
•
Drug-‐induced e
...
steroids
Different types
•
Cataracts may be partial or complete, stationary or progressive, or hard or soft
...
•
Nuclear sclerosis is the most common type of cataract and involves the central or 'nuclear'
part of the lens
...
•
Posterior subcapsular cataracts are cloudy at back of the lens adjacent to the capsule (or
bag) in which the lens sits
...
Management of cataract
•
If patient is symptomatic: Management is surgical removal (e
...
phacoemulsification) with
intra-‐ocular lens implant
Age Related Macular Degeneration (ARMD)
•
Age-‐related macular degeneration (AMD) is a medical condition which usually affects older
adults (“age related”) and results in a loss of vision in the center of the visual field (central
scotoma) because of damage to the macular region of the retina
...
•
Commonest cause of blindness in Western World in patients over 65
•
2 types: dry and wet
•
Wet ARMD is much less common and can cause rapid vision loss
...
New blood vessels
are weak and can rupture leading to haemorrhage and protein leakage (exudates) below the
macula
...
It can be treated with laser coagulation, and with medication that
stops and sometimes reverses the growth of blood vessels e
...
anti VEGF (anti-‐ vascular
endothelia growth factor)
...
In the dry
(nonexudative) form, cellular debris called drusen accumulates between the retina and the
choroid, and the retina can become detached
...
•
In the dry (nonexudative) form, cellular debris called drusen accumulates between the retina
and the choroid, and the retina can become detached
...
g
...
•
GIVE UP SMOKING
Symptoms
•
Gradual decline in vision
•
Central vision ‘missing’ (central scotoma)
Signs
•
Drusen: build up of waste products below RPE (retinal pigment epithelium) in particular in
the macula region
•
RPE (retinal pigment epithelial) changes: atrophy and hyperplasia
Management:
•
No cure: treatment is supportive with low vision aids e
...
magnifiers
•
Smoking cessation
Refractive errors
•
Myopia (short sightedness with long eye => problems with distant vision)
•
Hypermetropia or hyperopia (long sightedness with short eye => problems with near vision)
•
Presbyopia (age related long sightedness => problems with near vision)
•
Astigmatism (optical defect in which vision is blurred due to the inability of the optics of the
eye to focus a point object into a sharp focused image on the retina
...
•
The many different subtypes of glaucoma can all be considered to be a type of optic
neuropathy
...
•
It is normally associated with increased fluid pressure (IOP) in the eye
•
The nerve damage involves loss of retinal ganglion cells in a characteristic pattern: damage
occurs due to compression of the fundus from the raised IOP
•
Raised intraocular pressure (above 21 mmHg or 2
...
However, some may have high eye pressure for years
and never develop damage, while others can develop nerve damage at a relatively low
pressure
...
The angle refers to the area between the iris and cornea, through which fluid
must flow to escape via the trabecular meshwork
...
•
Open-‐angle, chronic glaucoma tends to progress at a slower rate and patients may not
notice they have lost vision until the disease has progressed significantly (“silent thief of
sight”)
...
Open angle glaucoma
•
2% of adult population (increases with age)
•
Drainage angle open (in contrast to acute closed angle glaucoma)
•
Intra ocular pressure increases gradually (chronic condition)
•
Intraocular hypertension caused gradual progressive damage of retinal nerve fibres
(particularly at the optic disc)
•
Visual field contracts (loss of peripheral vision) – also get Arcuate scotomas
•
Open angle glaucoma has been called the "silent thief of sight" because the loss of vision
often occurs gradually over a long period of time, and symptoms only occur when the
disease is quite advanced
...
•
Optician screening important: tonometry, VF, and optic disc
Pathophysiology
•
The underlying cause of open-‐angle glaucoma remains unclear
...
However, the major risk factor for most glaucomas is increased intraocular
pressure, i
...
ocular hypertension
...
•
Aqueous humor flows from the ciliary processes into the posterior chamber, bounded
posteriorly by the lens and the zonules of Zinn, and anteriorly by the iris
...
From here, the trabecular meshwork drains aqueous humor via
Schlemm's canal into scleral plexuses and the general blood circulation
...
The iridocorneal angle is open
...
•
NB: In closed (narrow-‐angle) glaucoma, the iridocorneal angle is completely closed because
of forward displacement of the final roll and root of the iris against the cornea, resulting in
the inability of the aqueous fluid to flow from the posterior to the anterior chamber and
then out of the trabecular network
...
Symptoms
•
Often none
•
Gradually progressive visual field loss in particular constriction of visual fields
Signs
•
Increased intraocular pressure (measured via ocular tonometry) > 21mmHg
•
Optic nerve changes: cupped disc (increased cup to disc ratio) on fundocopy examination
(due to thinning of neuroretinal rim and increasing size of cup) +/-‐ optic atrophy
•
Arcuate visual field defect (arcuate scotoma): an arc-‐shaped defect of vision extending from
the blind spot (optic nerve head) and arching into the nasal field following the lines of retinal
nerve fiber
•
Loss of peripheral fields
Management:
•
Pressure-‐lowering eye drops e
...
prostaglandin analogues (e
...
latanoprost) and CA
inhibitors (e
...
oral acetazolamide (diamox) or topical dorzolamide)
•
First line for open angle = PG analagoues and beta blocker (CIs include asthma, COPD and
heart block)
•
First line for closed angle = pilocarpine (opens angle) and acetazamolide (reduces aqeous
humour production)
•
Occasionally surgery
! Peripheral bilateral iridotomy for ACAG – as blockage as at the iridocorneal angle
! Trabeculectomy for closed angle glaucoma – as blockage is in trabecular network
•
Need constant monitoring in clinic with regular visual field testing
THE EYE IN SYSTEMIC DISEASE
Cardiovascular Disease
•
Diabetes (DM) – can cause DR or cataracts
...
•
Hypertension (HT) – can cause HT retinopathy
•
CV risk factors (smoking, HT, hyperlipidaemia, DM) – can cause variety of ocular problems
e
...
CRAO, CRVO, BRAO, BRVO, amuarosis fugax, DR etc
•
Vascular Occlusion
Inflammatory Disease
•
Granulomatous Disease
•
Giant Cell Arteritis
•
Thyroid Eye Disease
Connective Tissue Disease
•
SLE
•
Rheumatoid Arthritis
•
Marfans
Diabetic retinopathy
•
Diabetic retinopathy is retinopathy (damage to the retina) caused by complications of
diabetes, which can eventually lead to blindness
...
However abnormalities can be detected by
fundus photography (hence why DM patients have yearly fundoscopic screening)
...
If there is reduced vision, fluorescein angiography can be
done to see the back of the eye
...
Microaneurysms can rupture
and leak blood vessel contents into retina => dot, blot or flame-‐shaped haemorrhages
•
Diabetic retinopathy often has no early warning signs
...
In general,
however, a person with macular oedema is likely to have blurred vision, making it hard to do
things like read or drive
...
This can happen at all stages of NPDR
...
10 percent of diabetic
patients will get vision loss related with macular oedema
...
Can be Tx with macular grid photocoagulation or anti-‐VEGF
...
At this earliest stage, microaneurysms occur
...
At least one
microaneurysm, and also dot, blot or flame-‐shaped haemorrhages in all four fundus
quadrants
...
Intraretinal microaneurysms and dot and blot haemorrhages
of greater severity, in one to three quadrants
...
•
Severe Nonproliferative Retinopathy: Many more blood vessels are blocked, depriving
several areas of the retina with their blood supply
...
Signs of non proliferative diabetic retinopathy (NPDR)
•
•
Dot + blot haemorrhages
•
Hard exudates (due to excavation of proteins from ruptured microanerysms)
•
Cotton wool spots (caused by damage to nerve fibers and are a result of accumulation of
axoplasmic material within the nerve fiber layer)
•
Abnormalities of venous calibre e
...
venous beading
•
Microaneurysms
Intra-‐retinal microvascular abnormailities (IRMA)
Proliferative diabetic retinopathy (PDR): Neovascularisation
•
As the disease progresses, severe nonproliferative diabetic retinopathy enters an advanced,
or proliferative (PDR) stage when blood vessels proliferate and grow (e
...
neovascularisation)
...
•
These new blood vessels are abnormal and fragile
...
By themselves, these
blood vessels do not cause symptoms or vision loss
...
If they leak blood, severe
vision loss and even blindness can result
...
In most cases, it will leave just a few
specks of blood, or spots, floating in a person's visual field (e
...
floaters), though the spots
often go away after a few hours
...
•
These spots are often followed within a few days or weeks by a much greater leakage of
blood, which blurs vision
...
It may take the blood anywhere from a few days to months or even years to
clear from the inside of the eye, and in some cases the blood will not clear
...
•
Without timely treatment, these new blood vessels can bleed, cloud vision, and destroy the
retina
...
•
The new blood vessels can also grow into the angle of the anterior chamber of the eye and
cause neovascular glaucoma
...
•
New blood vessels (neovascularisation) along the retina and in the clear, gel-‐like vitreous
humour that fills the inside of the eye
...
e
...
•
It is usually associated with disease processes in the retina, which involve the retina
becoming starved of oxygen (ischaemic) e
...
DM
...
These factors stimulate the formation of new
blood vessels (angiogenesis)
...
Other conditions causing rubeosis iridis include central retinal vein occlusion
and chronic retinal detachment
...
Maculopathy is
damage to the macula which provides us with our high acuity central vision
...
•
One such cause of macular damage is from diabetic macular oedema whereby blood vessels
near to the macula leak fluid or protein onto the macula (due to ruptured
microanuerysms)
•
If the leakages cause the retina to harden (hard exudates) and exudates (deposits of fat and
protein from the blood) become significantly large and close to the fovea, then the condition
is termed as Clinically Significant Macular Oedema (CSMO) i
...
within one disc diameter
...
g
...
The aim is to kill iscaemic cells that are secreting VEGF
...
Manifestations of these changes include:
•
Attenuated blood vessels: copper wire arterioles or silver wire arterioles
Advanced hypertensive retinopathy causes microaneurysms which can result in:
•
Blot haemorrhages and/or flame haemorrhages
•
Cotton wool spots (ischemic changes causing damage to nerve axons)
•
Hard exudates
•
Retinal haemorrhage
•
Optic disc oedema (in severe cases)
•
NB: Optic disc swelling (oedema) can be caused by a number of conditions; papilloedema
relates more specifically to optic disc swelling secondary to raised intracranial pressure
...
•
Particularly in young patients
•
Very dramatic fundus appearance => pappiloedema
•
Can have decreased vision
Central retinal artery occlusion (CRAO)
•
Sudden painless loss of vision (“VARICOSE”)
•
Very profound loss of vision
•
Retinal nerve fibre layer becomes swollen except at fovea where we can observe a cherry
red spot (observation of choroid blood vessels deep to the macula; observed through the
thin ischameic retina)
•
Pale retina
•
Rarely recovers
Central retinal vein occlusion (CRVO)
•
Sudden painless visual loss
•
Range of visual loss
•
Pizza disc fundus
•
Need to determine degree of ischaemia
•
Ischaemia correlates to degree of reduced vision and fundal appearances
Branch vein occlusion
•
•
May be assymptomatic
•
Painless disturbance in vision
May be aware of loss of part of field
Infective diseases
The following infections can cause uveitis:
•
TB
•
Herpes Zoster
•
Toxoplasmosis
•
Candidiasis
•
Syphilis
•
Lyme Disease
Inflammatory Disease
Sarcoidosis
•
Sarcoidosis is a multi-‐system disorder involving abnormal collections of chronic
inflammatory cells (non-‐caseating granulomas) that can form as nodules in multiple organs
...
•
The combination of erythema nodosum, bilateral hilar lymphadenopathy, and arthralgia
(joint pain) is highly suggestive of Sarcoidosis
•
Manifestations in the eye include anterior uveitis, uveoparotitis, and retinal inflammation,
which may result in loss of visual acuity or blindness
...
g
bulging of the eyes)
•
Exophthalmos, also called proptosis, is a bulging of the eye anteriorly out of the orbit
...
Various mechanisms affect the development of lid lag in thyroid eye
disease
...
The
examiner then moves the finger slowly upwards and downwards, observing the
movement of the patient's eyes and eyelids
...
! Pigmentation
•
Restrictive myopathy of EOMs (opthalmoplegia) which may result in diplopia and
strabismus
Ocular:
•
Anterior Segment
! Chemosis (swelling/oedema of the conjunctiva)
! Exposure keratopathy (dryness of the cornea caused by incomplete or inadequate
eye-‐lid closure)
! Glaucoma
! Painful red gritty eye
•
Posterior Segment
! Choroidal folds (parallel grooves or striae involving the inner choroid)
! Optic nerve swelling
Management:
•
Control of thyroid dysfunction
•
Lubricants
•
Stop smoking
•
Surgical decompression
Connective Tissue Disease
SLE
•
AI disease
•
Multisystem immunological (AI) disease
•
Systemic lupus erythematosus (often abbreviated to SLE or lupus) is a systemic autoimmune
disease (or autoimmune connective tissue disease) that can affect any part of the body
...
•
It is a Type III hypersensitivity reaction in which antibody-‐immune complexes precipitate and
cause a further immune response (but no activation of the membrane attack complex)
•
SLE most often harms the heart, joints, skin, lungs, blood vessels, “blood”, liver, kidneys, and
nervous system
...
•
The disease occurs nine times more often in women than in men, especially in women in
child-‐bearing years ages 15 to 35, and is also more common in those of non-‐European
descent
...
g
...
•
Associated with RhF and Anti-‐CCP
Ocular effects:
•
Keratoconjunctivitis Sicca: which is a dryness of eyes and mouth caused by lymphocyte
infiltration of lacrimal and salivary glands
...
Dryness
leads to inflammation
...
The hallmark symptom of Sjögren's syndrome is a generalized dryness, typically including xerostomia
(dry mouth) and keratoconjunctivitis sicca (dry eyes)
...
•
People with Marfan tend to be unusually tall, with long limbs and long, thin fingers
...
Cardaic issues
...
•
Nearsightedness (myopia) is common
•
Farsightedness (hyperopia or hypermetropia) can also occur
•
Astigmatism is common: an astigmatism is an optical defect in which vision is blurred due to
the inability of the optics of the eye to focus a point object into a sharp focused image on
the retina
...
•
In Marfan syndrome the health of the eye can be affected in many ways but the principal
change is partial lens dislocation (the lens is shifted out of its normal position)
...
THE ACUTE RED EYE
Causes:
•
Conjunctivitis (most common): is inflammation of the conjunctiva (the outermost layer of
the scelera and the inner surface of the eyelids)
...
g
...
•
Anterior uveitis (also known as iridocyclitis and iritis): anterior uveitis is the inflammation of
the iris and anterior chamber (e
...
ciliary body)
...
Associated with cilliary flush (circumcorneal injection)
•
Posterior uveitis (also known as chorioretinitis): posterior uveitis is the inflammation of the
retina and choroid
...
Painless
...
•
Scleritis: much more severe inflammation that occurs throughout the entire thickness of the
sclera
...
Widespread
...
•
Acute closed angle glaucoma (ACAG): red eye, painful, headache, N&V, fixed mildly dilated
pupil, stoney hard eye
•
Subconjunctival haemorrhage: also known as hyposphagma, is bleeding underneath the
conjunctiva
...
When this happens, blood leaks into the space between the conjunctiva
and sclera
...
g
...
Often caused
by local spread from a sinus infection
...
Meibum prevents
tear spillage onto the cheek, trapping tears between the oiled edge and the
eyeball, and makes the closed lids airtight
•
Tears:
! Tears bathe corneal epithelial cells in a moist environment, preventing them from
drying out and weakening
...
! Furthermore, white blood cells can be transported to the corneal surface via the
tear film, and both toxic agents as well as debris can be diluted and washed away
by the tear film
...
IgA has been shown to prevent
bacterial binding
...
The
conjunctiva is also one of the closest vascularized tissues to the cornea
...
Not only does the conjunctiva produce
IgA, like the lacrimal glands, but it also contains macrophages, neutrophilic granulocytes,
mast cells, lymphocytes, and other aspects of the general mucosal (MALT) immune system
...
At the same time, corneal
epithelial cells also secrete cytokines to activate microbial defense
...
g
...
g
...
g
...
Common in viral infections or due
to surface irritation
...
g conjunctivitis
! Greatest around cornea (circumcorneal injection or ciliary flush) likely to
indicate intra-‐ocular problem e
...
keratitis (corneal inflammation) or anterior
uveitis (iritis) or glaucoma => much more worrisome
•
Cornea
! Clear (can see lens and pupil clearly) or hazy
! Foreign body
! Abrasion
! Ulcer
! Use fluorescein dye and blue light: stains any epithelial defect and fluoresces
green under blue light to reveal corneal damage
•
Anterior chamber (fluid-‐filled space inside the eye between the iris and the cornea's
innermost surface, the endothelium)
...
g
...
VA should always be assessed
...
g
constriction/miosis on focussing on near object)
•
Convergence: eye vergence and pupil constriction on looking at near object
•
CN examination
•
IOP (intraocular pressure) measured via tonometry
Also examine lymph nodes if suspect infection
...
g conjunctivitis
•
Greatest around cornea (circumcorneal injection) likely to indicate intra-‐ocular problem
(much more serious) e
...
keratitis (corneal inflammation) or anterior uveitis (iritis)
Blepharitis
Blepharitis is inflammation of the eyelid, the severity and time course of which can vary
There are three main types of blepharitis: staphylococcal blepharitis (anterior blepharitis),
seborrhoeic blepharitis (anterior blepharitis) and meibomian blepharitis (posterior blepharitis)
...
The underlying cause of seborrhoeic dermatitis is not clear
...
In seborrhoeic dermatitis, the affected skin becomes more oily and can become
scaly
...
g
...
g
...
g
...
5 to
1
...
g
...
g
...
g
...
g
...
with
pre-‐auricular
lymphadenopathy
i
...
Supportive Tx: cool compresses / lubricants
Don’t forget the possibility of chlamydial conjunctivitis, especially in:
! Young patient
! Bilateral
! Follicular conjunctivitis
•
Consider chlamydia PCR swab
...
•
Much more serious condition (compared to conjunctivitis)
•
Other characteristic symptoms include:
! Red eye (circumcorneal injection or ciliary flush) – in contrast to the forniceal
injection seen in conjunctivitis
! Moderate to intense pain
! Loss of vision
! Foreign body sensation
! Sensitivity to light (photophobia)
! Watery eyes (epiphoria)
! Blurred vision
...
Anatomical layers of the cornea:
•
Epithelium (anterior e
...
on surface of eye)
•
Stroma (middle connective tissue layer)
•
Endothelium (posterior e
...
over pupil and iris)
Examination
•
Use of anaesthetics if photophobic
•
Corneal reflection
•
Use of fluorescein (to detect damage) – organge liquid which will stain green with cobalt
blue light if damaged cornea
•
Vascularisation (not normally visible)
•
Opacity: the cornea is usually transparent and we can see the pupil and iris clearly
...
g
...
e
...
After
healing, this form of keratitis does not generally leave a scar
...
e
...
This can be reduced or avoided with the use of
topical corticosteroid eyedrops
...
Causes
•
Infective: Viral, fungal, bacterial, acanthamoeba (most common protozoa in soil, and
frequently found in fresh water and other habitats)
•
Immune: Rheumatoid arthritis, hypersensitivity (e
...
marginal ulcer, and rarely Wegener’s
granulomatosis, polyarteritis etc)
Symptoms
•
Red eye: circumcorneal injection (e
...
pertaining to the area of the eye surrounding the
cornea)
•
Severe pain: Corneal ulcers are extremely painful due to nerve exposure
•
Vision may be reduced e
...
g
...
g
...
g
...
Many causes
including drugs, Sjogrens disease, RA, and CN VII dysfunction (as facial nerve supplies
parasympathetic innervations to the lacrimal gland)
•
Neurotrophic keratitis e
...
HZ, HS
•
Vitamin deficiency e
...
Vit A – xeropthalmia and keratomalacia
•
Chlamydial CT keratitis
Bacterial Corneal Ulcers
•
Sight threatening (treat as in-‐patient)
•
Risk factors:
! Corneal abrasion (injury to surface of cornea) – very common in CL wearers
! CL (contact lens) wearer => also increases risk of corneal abrasions
! Dry eye (xeropthalmia)
! Iatrogenic
•
Corneal scrape to determine causative organism: Staph / Strep common
•
Tx: topical AB e
...
ofloxacin (quinolone AB) hourly – as serious infection
Herpetic Corneal Ulcers (dendritic ulcer)
•
Common
•
Occur due to HS virus
•
Ask about previous HS (herpes simplex) infections – gential warts, cold sores
•
Typical dendritic ulcer as shown below (very distinctive)
•
Treat with topical aciclovir 5 day (7-‐10 days)
•
DONT use of topical steroids (leads to geographic corneal ulcer)
Corneal ulcers treatment
•
Identify cause: swab, gram stain and culture
•
Bacterial ulcers can follow from an injury or from wearing contact lenses
•
Antimicrobials if infection e
...
ofloxacin for bacterial or acyclovir for viral -‐ HOURLY
•
Steroids if autoimmune (only give steroids once infection has been ruled out)
Anterior uveitis
•
Uveitis is inflammation of the middle layer of the eye, called the uvea or uveal tract (iris,
cliary body and choroid/retina)
...
•
Anterior uveitis: this is inflammation of the iris (iritis) or inflammation of the iris and the
ciliary body (iridocyclitis), and is the most common type of uveitis, accounting for about
three out of four cases
•
NB: Anterior uveitis is often missed and treated as conjunctivitis
Causes:
•
Majority of cases are idiopathic
•
Autoimmune: Reiter's, Ulcerative colitis (Enteropathic arthiritis), Ankylosing Spondylitis,
Sarcoidosis, all sero –ve spondyloarthropathies, RA
•
Infective e
...
T
...
Syphillis, HS (common), HZ (minority of cases)
•
Malignancy e
...
leukaemia
•
Other e
...
idiopathic, traumatic, secondary to other eye disorders etc
Symptoms
•
Pain +/-‐ referred pain
•
Red eye: circumcorneal injection
•
Vision may be reduced (blurred)
•
Photophobia (sensitivity to light)
•
Floaters (shadows that move across your field of vision)
•
Very similar symptoms to keratitis
Signs
•
Circumcorneal redness (injection)
•
Keratic precipitates
•
Cells / Flare in anterior chamber
•
Hypopyon (inflammatory cells in the anterior chamber of eye) if severe
•
Synechiae: condition where the iris adheres to either the cornea (i
...
anterior synechia) or
lens (i
...
posterior synechia)
•
Small pupil (miosis) and/or distorted pupil shape (due to synechiae)
•
Glaucoma
•
Granulomatous nodules
Anterior uveitis management
•
Topical steroids (unless infective) hourly – ONCE RULED OUT INFECTIVE
•
If infective treat with anti-‐micorbials or anti-‐virals and DO NOT give steroids
•
Topical mydriatics and cycloplegics (drugs which dilate the pupil e
...
tropicamide or
phenylephrine) to relieve pain due to cilliary spasm
...
However, in iritis, posterior synechiae (adhesions of iris to lens) results in pupil block =>
aqueous humour cant flow from posterior chamber to anterior chamber
...
g
...
•
Investigate for systemic associations if recurrent or chronic
Episcleritis
•
Episcleritis is a benign, self-‐limiting inflammatory disease affecting part of the eye called
the episclera
...
•
Episcleritis is a common condition, and is characterized by the abrupt onset of mild eye
pain and redness
...
•
The disease is often contracted through association with other diseases of the body, such as
Wegener's granulomatosis or rheumatoid arthritis or connective tissue disease
...
•
Painful and injection (redness) of deep vascular plexus
•
Widespread
•
Very painful
•
Phenylephrine test: Scleritis may be differentiated from episcleritis by using phenylephrine
eye drops, which causes blanching of the blood vessels in episcleritis, but not in scleritis
•
Associated uveitis common
Episcleritis versus scleritis
Acute closed angle glaucoma (ACAG)
•
Not common (open angle glaucoma is much more common)
•
Opthalamic EMERGENCY
•
In closed angle glaucoma the iridocorneal angle is completely closed because of forward
displacement of the final roll and root of the iris against the cornea, resulting in the inability
of the aqueous fluid to flow from the posterior to the anterior chamber and then out of the
trabecular network
...
•
Acute angle-‐closure glaucoma (AACG) occurs when the pressure inside your eye gets too
high very quickly
...
What causes the blockage?
•
The iridocorneal angle is the acute angle between the iris and the cornea at the periphery of
the anterior chamber of the eye
...
•
The trabecular meshwork is responsible for draining the aqueous humor from the eye via
the anterior chamber (the chamber on the front of the eye covered by the cornea), into a set
of tubes called Schlemm's canals which flow into the blood system
...
This situation results in an acute rise in intraocular pressure
(IOP) whih causes a number of symptoms and signs depending on the type of angle closure
...
For example, if the area near the base of the iris is very narrow, the trabecular
meshwork can get blocked more easily
...
Risk factors
•
Ocular hypertension
•
Medications e
...
eye dropswhich are used to dilate the pupil such as tropicamide
(anticholinergic which acts as a mydriatic)
...
Pupil dilatation (mydriasis) can precipitates ACAG (due to
iris expanding in size and becoming too close to the trabecular meshwork)
•
Night time => pupil dilation
•
Hypermetropia (long sigtedness with a short eye) => short eye with narrow anterior
chamber => decreased iridocorneal angle
•
Elderly due to presbyopia (age related hypermetropia/longsighthedness): People who are
farsighted are more likely to have eyes with shallow anterior chambers (short eye lengths)
and narrow angles, increasing their risk for angle-‐closure glaucoma from pupil dilation or
aging changes in the eye
...
g
...
Pilocarpine (muscarinic agonist) also acts on the ciliary muscle and causes it to contract (lens
accomodation)
...
This
action facilitates the rate that aqueous humor leaves the eye to decrease intraocular
pressure (miosis also helps due to effects on iris muscles)
...
The surgeon uses an Nd:YAG laser to create a small hole in the
peripheral iris
...
Fluid which is produced behind the iris has easier access to the eye's internal
drainage system
...
The primary goal of the procedure is to lessens the risk of
acute angle-‐closure glaucoma
...
Subconjunctival haemorrhage
•
•
Such a hemorrhage may be caused by a sudden or severe sneeze or cough, or due to
hypertension or as a side effect of blood thinners
...
•
Can also be caused due to trauma
•
PAINLESS
•
A subconjunctival hemorrhage is bleeding underneath the conjunctiva
...
When this
happens, blood leaks into the space between the conjunctiva and sclera
...
Summary
•
•
Injection results due to hyperaemia (the increase of blood flow to a tissue due to
vasodilation which is secondary to inflammation)
...
•
Conjunctivitis is the less serious but more common cause of red eye
•
Management includes assessing whether emergent action (including referral) is needed, or
whether treatment can be accomplished without additional resources
...
g
...
•
Red eye is a non-‐specific term to describe an eye that appears red due to illness or injury
...
Influenzae)
•
bacilli (Pseudomonas)
Ocular infections
•
Infection of the eyelids = Blepharitis
•
Infection of the conjunctiva = Conjunctivitis
•
Infection of the sclera = scleritis
•
Infection of the cornea = keratitis
•
Infection of the uvea (iris, ciliary body and choroid) = uveitis (posterior uveitis can also
involve the retina and other structures)
•
Infection of the intraocular cavities (e
...
the aqueous and/or vitreous humor) =
Endophthalmitis (suspect in infections after surgery)
•
NB: Panophthalmitis is inflammation of all coats of the eye including intraocular structures
...
It is commonly due to an infection (usually viral, but
sometimes bacterial) or an allergic reaction
...
By cause:
•
Allergic conjunctivitis (atopic conjunctivitis)
•
Bacterial conjunctivitis including chlamydial -‐ pappiale, purulent
•
Viral conjunctivitis – follciles, preauriculae lymphadenopathy, epiphroia
•
Chemical conjunctivitis
•
Neonatal conjunctivitis is often defined separately due to different organisms
...
•
Keratoconjunctivitis is the combination of conjunctivitis and keratitis (corneal inflammation)
Clinical features of conjunctivitis
Common to all forms of conjunctivitis
•
Red eye/injection (hyperaemia) – forniceal injection
•
Swelling of conjunctiva (chemosis)
•
Watering (epiphora) of the eyes -‐ more common in viral
•
NO LOSS OF VISION (but blurring may occur due to watering/discharge)
Bacterial conjunctivitis
•
Rapid onset of conjunctival redness (conjunctival injection around the conjunctival fornices
=> forniceal injection)
•
Swelling of the eyelid (chemosis)
•
Mucopurulent discharge => stickiness and crusting
•
Typically, symptoms develop first in one eye, but may spread to the other eye within 2–5
days
...
•
Severe crusting of the infected eye and the surrounding skin may also occur, but, contrary to
popular belief, discharge is not essential to the diagnosis
...
•
NO LOSS OF VISION
•
CONTACT HISTORY
Bacterial conjunctivitis common pathogens in children and adults:
•
Staph aureus: gram +ve, coagulase +ve Staphylococcus; blue gram stain with clusters
•
Strep pneumonia: gram +ve, alpha (partial) haemolytic Streptococcus; blue gram stain with
strips/chains
•
Haemophilus influenzae (especially in children): gram –ve, cocci-‐baccili, pink gram stain
•
Common bacteria responsible for non-‐acute bacterial conjunctivitis are Staphylococci and
Streptococci
Bacterial conjunctivitis pathogens in neonates:
•
Staph aureus
•
Neisseria gonorrhoeae
•
Chlamydia trachomatis
•
Refer all cases to ophthalmology
Treatment of bacterial conjunctivitis:
•
•
Topical antibiotic usually chloramphenical qds (four times a day)
•
Drops vs ointment
•
Avoid chloramphenicol if history of aplastic anaemia or allergy
•
Swab for M&C
Be aware of chloramphenicol allergy if worsening symptoms
Conjunctivitis in contact lenses wearers
•
Acanthamoeba (protozoa found in water)
•
Pseudomonas aeruginosa (gram –ve bacterium also found in water) – reistant to
chloramphenicol
•
Treat with ofloxacin rather than chloramphenicol
•
Be sure to rule our corneal abrasion keratitis, or ulcerative keratitis – fluroescien
Viral conjunctivitis
•
Viral conjunctivitis is often associated with an infection of the upper respiratory tract, a
common cold, and/or a sore throat
...
Pathogens
•
Adenovirus (most commonly cause illness of the respiratory system e
...
cold and
pneumonia)
•
Herpes simplex
•
Herpes zoster
Adenoviral conjunctivitis
Herpes simplex (HS) conjunctivitis
•
Primary infection most commonly manifests as blepharoconjunctivitis i
...
infection of lids
and conjunctiva that heals without scarring
...
•
Corneal involvement is rarely seen in primary infection
...
g
...
This
organism may also affect other parts of the body and can cause the sexually transmitted
infection chlamydia
...
It is characterized by white lumps in the undersurface of the upper eyelid
(conjunctival follicles or lymphoid germinal centres) and by non-‐specific inflammation and thickening
often associated with papillae
...
Active trachoma will often be irritating and have a watery discharge
...
The later structural changes of trachoma are referred to as “cicatricial trachoma”
...
These lashes will lead to corneal opacities and scarring and then to blindness
...
g
...
•
The bacteria involved is often Staphylococcus aureus
•
For contact lens wearers, the organism is commonly Pseudomonas aeruginosa (found in
drinking water)
...
•
Ophthalmological emergency e
...
ofloxacin (stronger than chloramphenicol)
•
Need admission for hourly drops -‐ OFLOXACIN
•
Daily review
•
Usually in association with other corneal pathology or contact lens wear
Clinical features:
•
Painful eye (moderate to severe)
•
Impaired eyesight (blurred vision)
•
Red eye (circumcorneal injection) due to blood vessel dilation (hyperaemia)
•
Often, the conjunctiva is also inflamed – keratoconjunctivitis
•
Discharge is usually present and may be watery, mucoid or purulent; notably, it is absent in
keratoconjunctivitis sicca
•
Pupil may be small due to reflexive miosis
•
Photophobia is common (worrying sign)
•
Fluorescein readily demonstrates any ulceration (an epithelial breach) – stains green under
cobalt blue light
•
Opaqueness of cornea
Bacterial keratitis with hypopyon
Viral keratitis
•
Herpes simplex keratitis (dendritic keratitis): Viral infection of the cornea is often caused by
the herpes simplex virus which frequently leaves what is called a ‘dendritic ulcer’ -‐ very
recognisable/distinctive appearance
•
Herpes zoster keratitis
•
Adenovirus
Herpetic (HS) keratitis
•
Very painful
•
Can be recurrent
•
Recurrences eventually result in reduced corneal sensation (corneal anaesthesia)
•
If treated with steroids can cause a corneal melt and perforation of the cornea (as steroids
cause immunosupression) => DONT give steroids
•
Tx with Aciclovir
•
Dendritic ulcer (seen below) is very characteristic
Adenoviral keratitis
•
Bilateral
•
Usually follows an URTI e
...
g
...
Can
accour due to a variety of causes including keratitis and uveitis
...
•
The anterior chamber is the fluid-‐filled space inside the eye between the iris and the
cornea's innermost surface, the endothelium
...
Orbital cellulitis
•
Orbital cellulitis is inflammation of eye tissues behind the orbital septum
...
When it affects the rear of the eye, it is known as retro-‐orbital cellulitis
...
g
...
•
The aqueous humour is secreted from the ciliary epithelium, a structure supporting the lens
...
Aetiology:
•
Post-‐surgical e
...
cataract surgery
•
Endogenous
Clinical features
•
Severe pain
•
Decreasing vision
•
Very red eye
•
Hypopyon
•
Loss of red reflex
Organisms:
•
•
Often conjunctival “commensals”
Most common is Staph epidermidis
Management:
•
Intravitreal injection of amikacin and vancomycin (used to Tx Staph epidermidis)
•
Topical antibiotics
Chorioretinitis
•
Chorioretinitis is an inflammation of the choroid (thin pigmented vascular coat of the eye)
and retina of the eye
...
•
If only the choroid is inflamed and not the retina, the condition is termed choroiditis
Pathogens:
•
CMV in AIDS or immunocompromised
•
Toxoplasma gondii (parasitic)
•
Toxocara canis (worm)
Clinical features:
•
Floaters (e
...
floating black spots)
•
Flashing lights (photopsia)
•
Blurred vision
•
Pain in the eye
•
Redness in eye
•
Sensitivity to light (photophobia)
•
Excessive tearing (epiphora)
Toxoplasmosis
•
Toxoplasmosis is a parasitic disease caused by the protozoan Toxoplasma gondii -‐ parasite
•
Mild flu like illness
•
A unilateral decrease in visual acuity is the most common symptom of toxoplasmic retinitis
...
g
...
Diagnosis of eye infections
•
Swabs for microscopy, culture, PCR, sensitivity (bacterial)
•
Swabs for PCR (viral and chlamydial)
•
Corneal scrapes in bacterial keratitis
•
Aqueous/vitreous sample for culture in endophthalmitis
•
Microscopy/culture for acanthamoeba (protozoa found in water which can cause infection
especially in contact lenses wearers)
•
Serology for toxoplasma and toxocara
Treatment of eye infections
Bacterial conjunctivitis
•
Usually resolves without treatment
•
Chloramphenicol: treats most bacteria except Pseudomonas aeruginosa
•
Ofloxacin for CL wearers (to cover Pseudomonas aeruginosa)
•
Fusidic acid: treats Staph
...
V): treats most gram negative bacteria including Coliforms, and Pseudomonas
aeruginosa
•
Topical oxytetracycline: for Chlamydial conjunctivitis (but adults may also need oral
azithromycin treament for genital chlamydia infection)
Herpetic conjunctivitis
•
Topical +/-‐ oral antivirals (aciclovir)
Bacterial keratitis
•
Ofloxacin (a quinoline): treats most gram negative bacteria including coliforms,
Pseudomonas aeruginosa, and Haemophilus influenzae
...
Pneumonia
•
HOURLY
•
Gentamicin and cefuroxime: this combination will treat most gram positive and gram
negative organisms
Dacryocystitis
•
Dacryocystitis is an inflammation of the nasolacrimal sac, frequently caused by nasolacrimal
duct obstruction or infection
...
Rememeber lacrimal gland receieves parasympathetic innervation from CN VII
Immunology
Hypersensitivity reactions
•
Type I atopic e
...
allergic conjunctivitis to cat or hayfever (IgE mediated release of histamine
and other inflammatory mediators e
...
leukotriennes)
•
Type II: cytotoxic: IgG/IgM/complement mediated + MAC (membrane attack complex
which causes lysis) killing via complement
•
Type III: immune complex: IgG/IgM/complement mediated but no activation of MAC
•
Type IV: delayed type hypersensitivity reaction (DTHS) – cell mediated e
...
CD4, CD8,
macrophages
Type 1 HS: Acute allergic conjunctivitis
•
Chemosis (oedema/swelling)
•
Redness (mainly due to vasodilatation e
...
hyperaemia)
•
Epiphora (excessive tears)
•
Pruritus (itching)
•
Often combined with rhinitis
•
Most common cause is hayfever – ask about allergies
Type II cytotoxic: Moorens ulcer
•
Moorens ulcer is autoimmune condition (AI)
•
Rapidly progressive, painful, ulcerative keratitis (cornea inflammation) which initially affects
the peripheral cornea and may spread circumferentially
Type III immune complex: Idiopathic Iritis
•
•
Uveitis is often immune complex mediated (type 3)
Examplues include SLE
Symptoms of acute anterior uveitis:
•
Progressive (over a few hours/days)
•
Unilateral (usually but not always)
•
Painful red eye
•
Blurred vision
•
Photophobia
•
Epiphora
Signs of anterior uveitis:
•
Visual acuity in the affected eye is often reduced
•
The pupil may be abnormally shaped (due to iris synechia) or of a different size to the
unaffected eye
...
•
Injection around the corneal limbus (edge of the cornea) is characteristic and referred to as
circumlimbal injection
...
•
The characteristic sign is the presence of cells in the aqueous humour
...
Hypopyon
•
Hypopyon is inflammatory cells in the anterior chamber of eye
...
It is a sign of inflammation of the anterior uvea
and iris, i
...
iritis, which is a form of anterior uveitis
...
Type IV delayed hypersensisivity eg
...
•
The granulomas (formed due to type 4 DTHS reaction) are most often located in the lungs,
joints, or the lymph nodes, but any organ can be affected
...
•
Sarcoidosis may be asymptomatic or chronic
...
g
...
Then try to clarify the problem by asking more specific
questions
...
•
Associated Features: red eye, discharge, photophobia, epiphoria, distortion, headache,
floaters/flashers, nausea, systematic enquiry
•
Timing and duration: how long? Intermittent or constant – how long?
•
Course: worsening, progressively, stable or improving
...
g
...
•
Severity: mild, moderate or severe
Visual Aberrations
•
Glare and haloes – can be suggestive of cataractas or ACAG
•
Visual distortion (other than blurring) and metamorphopsia (suggestive of wet type ARMD)
•
Flashing lights and floaters – can be suggestive of migraine, RD or VH
•
Double vision (diplopia): monocular or binocular, vertical, tilted or horizontal, better/worse
in any particular direction of gaze
...
Past ocular history
•
Does patient wear glasses or contact lenses?
•
Any known diagnoses?
•
History of amblyopia (lazy eye since childhood) squint
...
•
Endocrine disease e
...
thyroid
...
•
Ask about any OTC self-‐administered drops
...
g
...
•
Strabismus is present in about 4% of children
...
•
If strabismus is present when the patient looks with both eyes (binocular), the condition is
called manifest strabismus or heterotropia
...
Exotropia and
esotropia are also known as divergent or convergent squint respectively
...
This
condition includes exophoria, esophoria, hyperphoria, and hypophoria
...
•
Therefore we must perform the cover-‐uncover test to detect a latent squint
...
The paretic type is due to paralysis
of one or several muscles that are responsible for natural eye movements (muscular or
neurological cause)
...
•
Paralytic strabismus has many causes including oculomotor (CN III) nerve palsy, trochlear
(CN IV) nerve palsy, congenital CN IV palsy, abucent (CN VI) nerve palsy, myasthenia gravis,
and Graves disease (restrictive myopathy)
The Cover Test
The cover test is the test to detect and grade a squint
...
If more nasal => suggests
exotropia
...
Can only detect manifest squint
...
Some squints may be intermittent and only apparent when focussing is exerted at near
...
If the patient wears glasses a cover test should be carried out with and without glasses to see what
effect the glasses have on the size or control of the deviation
...
The norm being slightly nasal
...
If the reflection is more nasal than
normal this is suggestive of an exotropia
...
•
Using an occluder cover the “straight” (fixing) eye and observe the movement of the
uncovered eye
...
e
...
•
The uncovered eye moves out from its convergent position to take up fixation in an
esotropia
...
Exotropia (wall eyed)
•
Cover the “normal” fixing eye
...
•
The uncovered eye moves in (adducts) from its divergent position to take up fixation in an
exotropia
...
Manifest squint
•
A manifest squint (tropia strabismus) is an imbalance between the eyes
•
One eye needs to take up central fixation therefore the other eye will squint e
...
left
esotropia
...
•
In manifest squint, binocular vision is not present
...
Cover uncover test: latent squint
•
If the corneal reflections are symmetrical and no manifest deviation has been found, a latent
deviation (phoria strabismus) is suspected
...
e
...
Repeat with the other eye
...
g
...
The movement that is seen as the occluder is removed is a
recovery movement as fusion is regained (See figures 3 and 4 below)
•
Therefore, in the cover-‐uncover test, we cover both eyes (separately) and observe each
eye as it is uncovered
...
g
...
•
If the eye moves in as it is uncovered, it has been in a divergent position e
...
a latent
divergence or exophoria
...
g if an esophoria is found in the R, an esophoria will
also be found in the L
Esophoria
•
If the eye moves out as it is uncovered, it has been in a convergent position e
...
a latent
convergence or esophoria
...
A recovery movement is seen as the cover
is removed -‐ the eye moves out from its convergent position to regain binocular vision
...
g
...
•
Each eye diverges under cover in an exophoria
...
Alternate cover test: maximum deviation
•
The alternate cover test is used to elicit the maximum size of the deviation
...
This will completely dissociate the eyes and allow the
examiner to detect even very small latent deviations
...
•
A cover-‐uncover test will still need to be carried out to determine whether the deviation is
manifest or latent
...
There are three cranial nerves that supply the EOM:
•
Oculomotor (CN III): Medial rectus, inferior rectus, superior rectus, inferior oblique
...
•
Observe corneal reflections to ensure fixation is maintained throughout assessment
...
•
Move the pentorch into each of the other 8 of the 9 positions of gaze and carry out an
alternate cover test in each position
...
•
Look for changes in size and direction of the deviation
...
Also ask in which position of gaze the separation of the two images is greatest, which will
help diagnose the affected muscle
...
•
Know how to use a Snellen chart and document results
...
•
A 6/6 measurement is normal visual acuity
...
•
The use of a pin-‐hole and different types of spectacles should be understood
Pupil Examination
•
Inspect pupils initially: symmetry, size, shape
•
Pupillary light reflex (afferent CN II, efferent CN III parasympathetic fibres)
•
Pupil accommodation (CN III parasympathetic fibres) e
...
constriction (miosis) on focussing
on near object and dilation (mydriasis) on focussing on far object (howeve mydriasis =
sympathetic NS)
Pupillary light Reflex Anatomy
Understand, that the pupillary light reflex consists of a four neurones reflex arc:
•
1st neurone: Connects the photoreceptors in retina (photoreceptive ganglion cells) with the
pre-‐tectal nucleus (tectum) in the midbrain via the optic nerve
...
•
2nd neurone: Fibres travel bilaterally and connects pretectal nucleus to both the ipsilateral
and contralateral Edinger Westphal nuclei (parasympathetic CN III nuclei)
...
•
3rd neurone: Connects the Edinger Westphal nuclei (pre ganglionic fibres) to the ciliary
ganglion
...
•
Consensual response = Simultaneous constriction of the other pupil
...
Both
pupils should stay equally constricted
...
The lesion will result in an ipsilateral (relative) dilation of the pupil on
swinging light to affected eye
...
This is important for foccuing on near objects
...
g
...
•
Optic nerve / retinal => Complete afferent pupillary defect or RAPD (partial afferent defect)
! Marked defect => shining the light in the affected eye will result in no constriction
of either pupil e
...
Shining the light in the right
eye will result in constriction of both pupils
...
! Mild => shining the light in the affected eye will result in a slow constriction of
both pupils, but then a gradual dilation of both pupils
...
e
...
! In an abnormal swinging-‐light test (i
...
there is a RAPD) there is less pupil
constriction in the eye with the retinal or optic nerve disease
...
The affected pupil will appear to dilate on shinging the light into
it
...
g the pupils accommodate),
but do not constrict when exposed to bright light
...
In general, pupils that “accommodate but do not react”
are said to show light-‐near dissociation
...
If painful with
mydriasis then suspect a posterior communicating aneurysm (emergency)
...
NB: Oculosympathetic palsy (Horner’s Syndrome) and causes of Horner’s Syndrome (congenital,
carotid aneurysm, lesions of the neck, eg trauma or surgery, brain stem vascular disease or MS,
Pancoast tumour of the lung, etc
...
PUPIL REFLEX
UNAFFECTED IN HORNERS
...
Visual fields
•
•
Use simultaneous presentation of hands as screen for hemianopia with both of the patient’s
eyes open
...
•
Tell the patient to look into the open eye at all times
...
Repeat with the other eye
...
•
The examiner and subject should be seated approximately 70 -‐ 100cm apart (approx arms
length) such that the hand / fingers occupy a plane midway between them
...
Optic Disc Basics
Introduction
•
‘Optic Disc’ is frequently used to describe the portion of the optic nerve head clinically
visible on examination
...
•
The optic nerve itself is a cylindrical structure of approximately 50mm in length, between
the retina and the optic chiasm
...
•
When assessing a disc for glaucoma there are many subtle characteristics which should be
examined, and are covered in detail in the Glaucoma Evaluation Tutorial
•
At the very least, all one should remember for an assessment of the optic disc is “the 3 Cs” -‐
the cup, colour and contour
...
•
The borders of the optic disc should be clear and well defined
...
The orange-‐pink appearance of the neuroretinal rim represents healthy, well perfused
neuro-‐retinal tissue
...
e
...
These include advanced
glaucoma, optic neuritis, arteritic or non-‐arteritic ischaemic optic neuropathy or a
compressive lesion
...
g
...
g
...
g
...
This pale centre is devoid of neuroretinal tissue and is called the cup
...
A cup to disc ratio of 0
...
e
...
•
An increased cup to disc ratio may indicate a decrease in the quantity of healthy neuro-‐
retinal tissue and hence, glaucomatous change
...
A more comprehensive disc assessment tool is the DDLS (Disc Damage Likelihood
Score)
Examination Techniques
•
There are many methods by which one can exam the optic nerve
...
This hand held device is cheap and readily
available in most clinical settings
...
•
All methods described above rely on a degree of patient cooperation, but it is essential that
pupils are dilated (mydriasis) prior to the examination
...
This may be more difficult, or
longer, in those with dark irides, diabetics or concurrent ocular inflammation
...
The importance of using the lowest
illumination necessary
...
•
The focusing dial: clockwise (yellow/green/white) for plus convex (convergent) lenses (+1 to
+20), anti-‐clockwise (red) for minus concave (divergent) lenses (-‐1 to –35)
...
•
Observer should remove glasses unless astigmatic (and patient should remove glasses unless
very myopic) to enable the ophthalmoscope to be held as close as possible to the observer’s
eye
...
Keep top of
ophthalmoscope close to observer’s brow such that the ophthalmoscope aperture is close to
the eye
...
Ask patient to look directly ahead (focussing on
far object => pupil dilation => better view of fundus) or ask patient to look at a target – be
aware that this may be confusing since the observer may well block the target causing
patient confusion and eye movement and make allowances
...
Compare each R/R
...
•
Stand to the side of the patient (not in front), place hand on patient’s forehead (or shoulder)
and whilst keeping pupil aligned, move closer to eye from a slightly temporal approach -‐
coming in from approximately 45 degrees should help you to land on the optic disc
...
Dial
through the lenses towards 0 to bring retina into focus (follow the red reflex in)
•
The patient’s pupil is like a keyhole, the nearer you are the more you see, the observer
should bring the ophthalmoscope very close to the patient’s eye (3-‐5 cm) whilst keeping it
close to their own
...
The importance of pupil dilatation will be noted from lectures and practicals
...
•
Students should follow a methodical pattern of examination
...
Always go
back to the optic disc after looking at each arcade
...
g
...
Cup to disc ratio (CDR)
•
•
CDR = the proportion of the disc that is occupied by the cup
...
4 or CDR 0
...
But
opinions vary as to what CDR constitutes a glaucomatous disc some say 0
...
8
...
3 to 0
...
However this technique of evaluating the optic disc has been
shown to be inaccurate and highly variable in the way that it is recorded
...
Early glaucomatous changes
are subtle and may appear similar to normal optic discs
...
Even before glaucoma reveals its first symptoms, the ophthalmologist is able to determine the
morphological changes of the head of a damaged optical nerve (which is called the "optic disc") with
a simple fundoscopy examination
...
g
...
g
...
It is
composed of millions of retinal nerve fibers that bundle together and exit to the brain
through the optic disc located at the back of the eye
...
The optic nerve head, often called the disc, is mostly filled with fibers
...
We all want to have lots of fibers, so we want a big rim (and by subtraction,
a small cup)
...
The bigger the ratio, the more empty space there is in the nerve
head
...
Most persons in the population
average a cup/disc ratio of about 0
...
7 or greater happen only 2
...
This causes the cup to
become larger in comparison to the optic disc, since the support structure is not there
...
•
A cup to disc ratio greater than 0
...
Optic disc pallor
Optic disc pallor refers to an abnormal coloration of the optic disc as visualized by a fundoscopic
examination
...
With optic disc
pallor, an abnormal pale yellow color is evident
...
In the photo of the eye above, the neuroretinal rim is much whiter than in the normal optic disc
...
The loss of the small capillaries within the
nerve accounts for the shift from orange-‐pink to white
...
First, the color change may be very subtle
...
Third, a cataract may
make a pale disc look orange
...
Optic cup deepening
•
Can occur as a result of the increased pressure acting on the optic disc
Optic disc and cup
Examination of the Eye & Vision
Introduction
•
Wash hands
•
Introduce yourself
•
Confirm patient details (name + DOB)
•
Explain examination
•
Gain consent
•
Appropriately position the patient
•
Ask if the patient is any pain or discomfort
•
Ask if the patient is comfortable before proceeding
Visual Acuity
1
...
g
...
Fine print reading
•
Ask patient to cover one eye
•
Ask patient to read a paragraph of small print in a book/newspaper
•
Repeat with the other eye
•
If they normally wear glasses for reading, ensure these are worn for the assessment
Visual Fields
•
Sit directly opposite the patient, at a distance of around 1 metre
•
Ask patient to cover one eye with their hand
•
If the patient covers their right eye, you should cover your left eye (just mirror the patient)
•
Ask patient to focus on your face & not move their head or eyes during the assessment, you
should do the same and focus your gaze on the patients face
•
Ask the patient to tell you when they can see your fingertip wiggling
•
Position your fingertip at the border of one of the quadrants of your visual field
•
Slowly bring your fingertip inwards, towards the centre of your visual field until the patient
sees it
•
If you are able to see your fingertip, but the patient cannot, this would suggest a reduced
visual field
•
Repeat this process for each quadrant, then repeat the entire process for the other eye
•
Document your findings
Visual neglect / inattention
•
Sit directly opposite the patient, at a distance of around 1 metre
•
Ask patient to focus on your face & not move their head or eyes during the assessment
•
Hold both arms out, with your fingers in the periphery of both yours & the patients field of
vision
•
Remind the patient to keep their head still & their eyes fixed on your face
•
Ask patient to point at which fingers are moving
•
Move the fingers of left & right hand in whichever order you choose
•
Then move the fingers of both hands simultaneously
•
If the patient only points to one of the hands, when fingers are moving on both hands, this
would be suggestive of visual neglect
•
Visual neglect can suggest damage to the frontal or parietal lobes of the brain e
...
stroke,
trauma, etc
CAN ALSO ASSESS FOR BLIND SPOTS
Pupils
Pupil inspection
•
Size (normal, miosis, mydriasis)
•
Shape (irregular shape may be a sign of uveitis)
•
Symmetry: aniscoria = different sized pupils
Pupil reflexes: 4 TESTS
To best see pupillary reflexes, the room should be dimly lit => pupils dilate
...
•
Direct pupillary reflex: Shine light into the pupil & observe constriction of that pupil
...
g
...
This time observe the
contralateral pupil
...
Lack of a normal consensual response may suggest: damage to optic nerve
shining light in, or damage to the Edinger Westphal Nucleus, or damage to CN III
•
Swinging light test: Move the pen torch every 3 seconds between the 2 pupils This test may
detect a relative afferent pupillary defect (RAPD) -‐ caused by damage of the tract between
the retina & optic chiasm, such as optic neuritis in multiple sclerosis
...
A RAPD can be detected by paradoxical dilatation of the affected pupil
when light is shining into it (it should normally constrict)
...
Then ask them to
focus on a much closer object (often a finger or pen torch)
...
Use corneal reflections
...
On covering the eye observe the uncovered eye
...
Onserve the covered eye on uncovering
...
g
...
Fundoscopy
Preparation
•
Darken the room
•
Warn pt will have to get very close to them
•
Ideally the patient should have their pupils dilated with short-‐acting mydriatic eye drops
(e
...
0
...
Dial up a +0
...
The red reflex is caused by light reflecting back from the vascularised
retina
...
Compare R and L red reflex
...
Comment
on the external structures I am observing while moving in
...
Begin medially & assess the
optic disc: colour, contour, cupping, shape and size, venous pulsation, drusen,
neovascularisation
•
Assess the retinal vessels in all 4 arcades (ask pt to look in direction foarcade I am
examining) – going back to the optic disc after each arcade: cotton wool spots, AV nipping,
neovascularisation, dot/blot or flame haemorrhages, drusen
•
Finally assess the macula: ask patient to look directly into the light
...
g
...
The lacrimal gland received parasympathetic innervations from CN
VII (facial nerve)
Ophthalmology: sample exam questions
1
...
Patient presents with a suspected squint => what tests should we carry out? What is the type of
squint?
•
Hirschberg test: It is performed by shining a light in the person's eyes and observing where
the light reflects off the corneas (comparing right and left)
...
When doing the
test, the light reflexes of both eyes are compared, and will be symmetrical in an individual
with normal fixation
...
! In exotropia the light lands on the medial aspect of the cornea
...
! In hypertropia the light lands on the inferior aspect of the cornea
...
! A cover test can tell you the extent of the eso/exotropia
•
The example above shows a manifest right convergent (esotropia) squint
...
We can say it convergent (esotropia) as the light reflex is on lateral
aspect of cornea
...
•
A manifest squint (tropia) is an imbalance between the eyes
...
However remember
on cover test when the squinting eye takes up fixation the other eye will deviate
...
If a manifest squint is detected do not go on to look
for a latent squint
...
There are three stages to the cover test:
! 1
...
The norm being slightly nasal
...
Using an occluder cover the “straight” (fixing) eye
and observe the movement of the uncovered eye
...
e
...
If the uncovered eye moves in to take up
fixation, it has been in a divergent position i
...
a manifest divergent squint or
exotropia
...
The cover/uncover test (as you remove the occluder watch the eye that has
been underneath to assess for latent deviation): If the corneal reflections are
symmetrical and no manifest deviation has been found, a latent deviation
(phoria) is suspected
...
e
...
Repeat with the
other eye
...
The movement that is seen as the
occluder is removed is a recovery movement as fusion is regained
...
e
...
If the eye moves in as it is uncovered, it has been in a
divergent position i
...
a latent divergence or exophoria
...
The alternate cover test – to find maximum deviation (manifest or latent): The
alternate cover test is used to elicit the maximum size of the deviation
...
This will completely dissociate the eyes and allow
the examiner to detect even very small latent deviations
...
A cover-‐uncover
test will still need to be carried out to determine whether the deviation is
manifest or latent
...
Patent has been asked to look in various directions, which muscle(s) is not working, and what is
the CN which supplies that muscle
•
Lateral rectus palsy in the right eye => failure to abduct right eye
•
Lateral rectus is supplied by CN VI (abducent nerve)
•
Righ CN VI palsy
•
Note the patient also has an esotropia on looking foreward
4
...
g
...
g DM retinopathy), the gel will “hold onto” the blood which can
cause vision loss
•
Retinal detachment
•
Optic neuritis
5
...
g
...
This value (x) represents the distance at which the letters become unclear to an
individual with normal eyes x metres away e
...
5=> this line of letters would be unclear to
normal eyes at 5 metres distance
•
In the most familiar acuity test, a Snellen chart is placed at a standard distance: 20 ft in the
US, or 6 metres in the rest of the world
...
•
Examples
! 6/6 is normal
! 6/5 means what a normal person sees from 5 metres away, you see from 6
metres
! 6/9 is poor vision, what you see from 6 metres a normal person sees from 9
6
...
What is this
clinical sign, and should we wake an ophthalmologist in the middle of the night to assess patient?
•
The coloured clinical photograph above clearly shows hyphema
•
A hyphema is a pooling or collection of blood inside the anterior chamber of the eye (the
space between the cornea and the iris)
...
g
...
When describing the optic disc use the 3Cs:
•
Colour
•
Contour
•
Cup
•
+ shape and size
•
Venous pulsation
•
Drusen
•
Neovascularisation
Can also comment on blood vessels (always come out at nasal side)
8
...
What is this lesion? What is the name of the dye it has been stained with and what is the topical
medication you would definitely NOT gave this patient?
•
Dendrtitic ulcer (type of corneal ulcer) caused by HSV (herpes simplex virus) – very
distinguishable
•
The eye has been stained with fluorescein dye (orangey colour) => shows up epithelial
damage (yellowish/green colour) on cornea which is enhanced by cobalt blue light
•
NEVER GIVE THESE PATIENT STEROIDS => high risk of geographical ulcer which can perforate
and is very hard to treat
9
...
g
...
g
...
g
...
How to describe a fundus
•
R or L eye
•
Disc:
! Contour: a healthy disc has well delineated margins where you can easily see
where the disc ends and retina starts
! Colour: a healthy disc is normally pink to orange in color with a paler cup
! Cup: a healthy disc has a small cup to disc ratio (<0
...
fluid can be reabsorbed and
proteins left beyond (which appear as yellowish lesions)
! Cotton wool spots
! Vessel abnroamlities
! Neovascularisation
•
Lesion description (as in previous question)
Title: Ophthalmology lecture notes
Description: A very comprehensive and detailed set of notes covering all aspects of ophthalmology. Complete with a nice set of diagrams to aid learning. Useful for medical students.
Description: A very comprehensive and detailed set of notes covering all aspects of ophthalmology. Complete with a nice set of diagrams to aid learning. Useful for medical students.