Eye Flashcards
Anterior segment components (5)
Cornea, conjunctiva, iris, ciliary body, crystalline lens
Posterior segment components (5)
Retina, choroid, sclera, vitreous humour, optic nerve
Corneal transplant now transplants the ___ layer of the cornea
endothelial layer (endothelial keratoplasty)
What forms the angle of the anterior chamber? What lies within the angle?
Corner between cornea, sclera, iris and ciliary body
Trabecular meshwork
Accommodation reflex of the lens
Far distance: ciliary muscles relax, suspensory ligaments become taut, lens become less convex
Near distance: ciliary muscles contract, suspensory ligaments become loose, lens become more convex
__ are for light vision, ___ for colour vision
rods
cones
Fovea
- highest density of __
- no ___
cones, rods
Optic disc is more __, macula is located __ to optic disc, in between ___ and ___
nasal
temporal
superior and inferior arcades
Fibres of optic radiation in the ___ lobe (aka ___ loop) represent the superior visual field. (pie in the sky)
temporal lobe
Meyer’s loop
contralateral superior homonymous quadrantanopia
Fibres of optic radiation in the ___ lobe (aka ___ loop) represents the inferior visual field. (pie on the floor)
parietal lobe
Baum’s loop
contralateral inferior homonymous quadrantanopia
Homonymous hemianopia is caused by ___ lesions. The ___ the lesion from the chiasm, the more ___ the hemianopia.
retrochiasmal lesions
further from chiasm, more congruent lesion (VF defect looks the same on both sides)
Name the parts of the visual pathway
Optic nerve -> optic chiasm -> optic tract -> lateral geniculate body -> optic radiation -> occipital lobe
What defect causes bitemporal hemianopia
Chiasmal lesions
What defect causes homonymous hemianopia with macular sparing?
Defect in the occipital lobe from PCA infarct with MCA intact
Tip of occipital lobe serves central visual field. Supplied by both MCA and PCA
Large occipital lobe damage can cause loss of macular sparing too
Patients with defect in superior visual field -> suspect ___ -> check for concomitant ___
pituitary adenoma
hyperprolactinemia (galactorrhea, gynaecomastia, amenorrhea)
Snellen chart 6/20 means?
At 6 metres, patient can see what a normal person can see at 20m
What is the pinhole effect?
focuses light by blocking peripheral light rays, corrects refractive errors up to -4D or +4D but cannot overcome organic/structural disease
Eyelid turn inwards: ___
eyelid turn outwards: ___
entropion
ectropion
Use ___ in ___ light to highlight corneal epithelial defects
Fluorescein strips in cobalt blue light
What is hyphema
Collection of blood in anterior portion of iris
what is hypopyon
Collection of leukocytic exudate in anterior portion of iris
seen in inflammatory conditions (eg uveitis) or infections (endopthalmitis)
What is the eclipse sign?
Shine light from temporal aspect of cornea towards nose to see width of shadow of iris in nasal area
Shadow broad = anterior chamber shallow = angle may be narrow = risk of angle closure glaucoma
What are the pupillary reflexes
Direct light reflex
Consensual
Relative afferent pupillary defect (RAPD)
Light near dissociation
Do the ___ to check for strabismus
Hirschberg corneal light reflex
What to look out for when checking optic disc
Colour: pink
Cup-disc ratio: normal = 0.3
Contour: edges
Margins: clear, blurred
Myopia = eyeball ___
hypermetropia = eyeball ___
astigmatism =
presbyopia =
myopia - eyeball long, light rays focused in front of retina
hypermetropia - eyeball short, light rays focus behind retina
astigmatism = inequality in refractive surface of the eye along 1 axis (rugby ball shape)
presbyopia = loss of lens elasticity and convexity due to aging, loss of accommodative ability
Prescription
Spherical = degree of ___
Cylinder = degree of ___
Axis =
myopia/hypermetropia
astigmatism
axis at which astigmatism power lies
Causes of acute visual loss (media opacity causes)
Media opacity
- painful, red: corneal ulcer, endopthalmitis, uveitis, acute angle-closure glaucoma
- painless, not red: vitreous haemorrhage
Causes of acute visual loss (retinal disease)
retinal detachment
painless:
- retinal vein occlusion
- retinal artery occlusion
Causes of acute visual loss (optic nerve disorders)
inflammatory:
- pain with ocular movement: optic neuritis
ischemic:
- painless: ischemic optic neuropathy
compressive optic neuropathy
Causes of chronic visual loss
Glaucoma - peripheral vision loss
age related macular degeneration - central vision loss
cataracts - general blurring
10 differentials for red eye
1) Allergic conjunctivitis
2) Infection: blepharitis, cellulitis, conjunctivitis, keratitis, endopthalmitis
3) Inflammation: episcleritis, scleritis, uveitis
4) Trauma: FB, chemical injury
5) Glaucoma
papillae vs follicles
1) papillae
- fibrovascular mounds with central vascular tuft
- seen in allergic conjunctivitis
2) follicles
- small translucent, avascular mounds of plasma cells and lymphocytes
- seen in viral keratoconjunctivitis
Only ___ and ___ problems causes RAPD
retina
optic nerve
Methods to assess visual acuity in preverbal children
- Observe fixation and following
- Fixation preference: getting upset when good eye is occluded
__ cards to test forced preferential looking in children 6mo-2yo
Teller
Striped patterns on one side appeal more to child, child looks at stripe over plain
Snellen chart used in children more than __
4yo
Pathophysiology of amblyopia?
Abnormal visual stimulation during visual development -> disruption in development of lateral geniculate nucleus and primary visual cortex
Unilateral: difference in BCVA is 2 or more Snellen lines
Bilateral: BCVA of 6/12 or less
Causes of amblyopia
1) Strabismus
- child’s brain suppresses image from non-fixating eye to avoid diplopia
- cortical suppression of sensory input from eye
2) Stimulus deprivation
- occlusion of visual axis (eg. cataract, ptosis)
3) Refractive error
- anisometropia (difference in 2 eyes): hyperopia >1.5D, myopia > -3-4D, astig >1.5D
- ametropia (both eyes high deg): hyperopia >5D, myopia <-8D
Tx of amblyopia
1) Occlusion therapy
- Gold standard
- Cover good eye to force fixation by amblyopic eye
2) Provide clear retinal image
- identify and correct refractive error with spectacles
- remove obstacles in vision (eg. ptosis, cataracts)
Treatment of amblyopia is critical before __ years old
8 years old
Best to correct during infancy/childhood
Inward deviation of eye known as ___
Outward deviation known as ___
esotropia
exotropia
___ most common strabismus in children
Intermittent exotropia
- more apparent when child is tired/daydreaming
How to assess strabismus
1) Hirschberg corneal light reflex
- 1mm deviation = 7 degree squint
2) Cover-uncover
3) Alternate cover
4) Stereopsis - depth perception
Cx of strabismus
1) Amblyopia - deviated eye
2) Poor binocular vision - ability to appreciate depth or stereovision
3) Abnormal head posture
Comitant vs incomitant strabismus
Comitant
- non-paralytic
- congenital, accomodative, intermittent
Incomitant
- paralytic, eye movement limited from EOM paralysis
What is leukocoria
White reflex - needs urgent referral
Absent red reflex also needs to be referred
Causes of leukocoria
1) Retinoblastoma
2) Congenital cataracts
3) Retinopathy of prematurity
Features of retinoblastoma
- Presents ~18 months
- RB1 gene on chr 13q14
- Features: leukocoria, strabismus, reduced vision, change in eye appearance, eye pain
Secondary cause of cataracts in children
TORCH infections
Trauma
Drug exposure
RB
Radiation
What is retinopathy of prematurity? Risk factors
Abnormal vascularisation of retina in premature child
RF:
- early gestational age, low birth weight
- Supplemental O2
- Unstable clinical course post delivery
Triad seen in congenital glaucoma
Blepharospasm - squeezing of eyes
Epiphora - tearing
Photophobia
Causes of ophthalmia neonatorum
1) Neisseria gonorrhea (3-5 days after birth)
- can cause corneal perf
2) Chlamydia trachomatis (5-14 days after birth)
3) HSV (1-2 weeks)
Trichiasis vs distichiasis
Trichiasis - normal eyelashes growing posteriorly towards eye
Distichiasis - eyelashes growing at abnormal positions
The Valve of ___ fails to open in congenital nasolacrimal duct obstruction
Hasner - closed at birth and opens by 1st month of life
Stye vs chalazion
Stye
- blocked oil gland on edge of eyelid
- staphylococcal abscess of lash follicles and associated glands
Chalazion
- infected meibomian gland
- nodule within tarsal plate
Features of preseptal cellulitis
- infection of subcutaneous tissue anterior to orbital septum
- due to periorbital trauma or dermal infection
- erythema, eyelid tenderness
- usually NO systemic illness
tx: oral augmentin, warm compress, topical abx
features of orbital cellulitis
- SIGHT & LIFE THREATENING EMERGENCY
- infection & inflammation within orbital cavity
- usually spread from ethmoidal sinuses
- pain, proptosis, chemosis, opthalmoplegia
- decreased visual acuity, RAPD
- FEVER/toxicity
- requires admission and septic workup, CT orbits
- IV abx, abscess drainage
Conjunctivitis caused by ___ can lead to corneal perforation
neisseria gonorrheae
What is endopthalmitis
Infection of vitreous and aqueous humour
- secondary to trauma, ocular surgery, immunocompromised states
Important to ___ when evaluating for foreign body
flip the eyelid
In chemical injuries, ___ is more damaging to the eye than ___
alkali - saponification of fatty acids in tissue
acid - coagulates tissue proteins, layers of precipitated protein buffers and limits acid penetration through cornea
What is enopthalmos
Eye sinking deeper into socket secondary to orbital floor fracture
How does diabetes cause diabetic retinopathy
hyperperfusion -> increase in shear stress -> damage to pericytes -> capillary leakage -> exudation and oedema
advanced glycation end prodycts -> microvascular occlusions -> hypoxia -> ischemia
Features of mild NPDR
microaneurysms due to weakened arterioles/capillaries
Features of moderate NPDR
flame-shaped haemorrhages
dot-blot haemorrhages
hard exudates - leakage of proteins and lipids from microaneurysms
retinal oedema
features of severe NPDR
4-2-1 rule (any of the following)
4 quadrants of dot blot haemorrhages
2 quadrants of venous beading, looping, segmentation
1 quadrant of intraretinal microvascular abnormalities (IRMA) - dilated vessels
cotton wool spots
What are cotton wool spots and what do they indicate
Nerve fibre infarcts from local ischemia
indicates severe NPDR, hypertensive retinopathy
ways diabetes can present in the eye
- non-proliferative diabetic retinopathy
- diabetic maculopathy (macular oedema)
- proliferative diabetic retinopathy
what is proliferative diabetic retinopathy
neovascularisation as a response to retinal ischemia
New vessels at disc (NVD)
New vessels elsewhere (NVE) - grows from arterial arcades
Complications of proliferative DR
- abnormal vessels break, causing vitreous haemorrhage (floaters, vision loss)
- hard exudates cause tractional retinal detachment
Management of diabetic retinopathy
- optimise systemic risk factors
- pan-retinal photocoagulation
- macular laser
- surgery: vitrectomy
Principle of pan retinal photocoagulation
Kill peripheral tissue -> reduce blood demand in the peripheries of the retina -> ensure sufficient blood flow to central retina -> preserve central vision
Features of hypertensive retinopathy
1) Arteriolar narrowing - AV nipping (constriction at junctions where arterioles and venules cross)
2) cotton wool spots
3) silver wiring - arterioles where central light reflex occupies entire width
4) optic disc oedema
What is seen in retinal photograph of central retinal artery occlusion
Cherry red spot (blood supply to fovea is by separate artery)
Pale retina
attenuation of retinal arterioles
What is seen in retinal photograph of central retinal vein occlusion
Blood and thunder appearance (flame and blot haemorrhages)
Cotton wool spots
Vascular tortuosity
Investigations in thyroid eye disease
thyroid panel
CT orbit - fusiform enlargement of extraocular muscles that SPARES TENDON INSERTIONS
In patients with MG, always do a ___ to look for ___
CT/MRI of anterior mediastinum
thymoma (15% have)
Most common eye infection in AIDS patients
CMV retinitis
- cheese and ketchup appearance (thick white infiltrate with retinal haemorrhage)
- others: kaposi’s sarcoma, molluscum, herpes zoster, syphilis
Keratoconjunctivitis sicca (aka ____) is seen in ___ and ___
dry eyes
rheumatoid arthritis
systemic lupus erythematosus
Nerve impulses in the afferent pathway of the pupillary light reflex are consolidated at the ____ before being transmitted to the efferent pathway
Edinger-Westphal nucleus
Ways to test visual field (clinical and objective)
Clinic
1) Amsler chart - central vision
2) Confrontation - finger counting, hand movement, light perception
3) Red targets - colour saturation less in visual defect
Objective
- humphrey perimeter (most sensitive, used nowadays)
- bjerumm screen
- goldmann perimeter
Defects in parasympathetic efferent pathway causes anisocoria worse in ___ light, due to failure in ___
Defective side has pupil that is ___ than normal
bright
fail to constrict
larger
Defects in sympathetic efferent pathway causes anisocoria worse in ___ light, due to failure in ___
Defective side will have pupil that is ___ than normal
low light
fail to dilate
smaller
Causes of parasympathetic anisocoria
3rd nerve palsy
- dilated pupil + partial ptosis + affected eye rests at down and out position
Adie’s tonic pupil
Traumatic rupture of pupillary sphincter
How to test for correction of parasympathetic anisocoria?
Administer pilocarpine eyedrops
- 3rd nerve palsy: will constrict with 1% pilocarpine
- Adie’s: will constrict with 0.1% pilocarpine
- Traumatic: will not constrict
Triad seen in Horner’s syndrome
Ptosis, miosis (constricted pupil), anhidrosis
Defect in sympathetic efferent pathway -> constricted pupil that fails to dilate in the dark
What can cause diplopia (classify)
Extraocular muscle disease
- thyroid eye, myositis
NMJ disease
- MG
Oculomotor nerve disease
- CN 3, 4, 6 palsy
Brain disease
- progressive supranuclear palsy
In suspected 3rd nerve palsy, always check for ___. Reason?
pupil involvement
Nerve fibers in CN3 supplying pupils are more peripheral
Compressive structures would compress these fibers first -> pupil involvement (dilation)
Ischemia would affect central CN3 fibers first -> no pupil involvement
In CN 6 palsy, need to exclude ___, as this causes ____
raised ICP
CN6 to be stretched along sharp edge of petrous temporal bone
What happens in acute angle closure glaucoma
Peripheral iris blocks outflow of aqueous humour from posterior to anterior chamber
due to shallow anterior chamber, thicker lens
RF
- female
- age >60 yrs
- hypermetropia (far-sightedness)
- racial group (eskimos > asians > caucasians)
Signs of acute angle closure glaucoma
Circumciliary injection
Semi-dilated, non-reactive pupil
Raised IOP - eye feels hard
Corneal oedema - can cause acute vision loss
Gonioscopy shows narrow angles
Types of retinal detachment
Rhegmatogenous
- retinal tear: tear in retina allows vitreous fluid to separate neurosensory retina from underlying retinal pigment epithelium
Non-rhegmatogenous
- exudative
- tractional
Risk factors for rhegmatogenous retinal detachment
- high myopia
- acute posterior vitreous detachment
- advanced age
- trauma
- retinal degeneration
Sx of retinal detachment
- flashes, floaters
- partial visual field defect
- +- RAPD
How to treat retinal detachment
Relief traction - scleral buckle, vitrectomy
Seal breaks - photocoagulation, cryotherapy
What causes cataracts
opacification of crystalline lens
Steroid use is associated with ____ cataracts
Posterior subcapsular cataract
Complications of cataracts
- increased myopia
- monocular diplopia
(leakage of lens proteins causes)
- lens induced glaucoma
- uveitis
Types of cataract surgery
1) intra-capsular
- lens + capsule removed
2) extra-capsular
- capsule retained, allows IOL implantation
- large wound, prolonged recovery
3) phacoemulsification
- ultrasound to emulsify cataract
- irrigation + aspiration to remove residue
- small wound, no sutures, quicker recovery
Types of intraocular lens
1) monofocal: vision at specified distance
2) multifocal: vision at various distances
+ toric: to reduce astigmatism
Glaucoma causes ___, which can lead to ___ and ___
raised intraocular pressure
optic nerve damage and visual field loss
What happens in primary open angle glaucoma
Cornea is not near iris, but aqueous humour not draining due to issues with trabecular meshwork
Glaucoma presents with loss of ___ vision, becomes ____ when advanced
loss of peripheral vision
tunnel vision
Triad in assessment of glaucoma
Increased optic disc cupping
- cup-disc ratio >0.3-0.4
Raised intraocular pressure
- measured with tonometer
Visual field defect
- Humphrey perimetry test
Acute management of glaucoma
Topical eyedrops
- beta blockers (timolol) : reduce aqueous production
- prostaglandin analogues (xalatan): increase uvoscleral outflow
- miotics (pilocarpine): open trabecular meshwork
- carbonic anhydrase inhibitor (dorzolamide)
Definitive management of glaucoma
Peripheral laser iridotomy - closed angle
Trabeculoplasty - open angle
Trabeculectomy - creation of fistula between anterior chamber and sub-conjunctival space
Normal structure of the retina
Choroid layer - provides blood supply
retinal pigment epithelium & Bruch’s membrane - separate choroidal layer from retinal neurons
Layer of retinal neurons
What causes age-related macular degeneration
- Progressive damage to RPE and Bruch’s membrane
- formation of drusen (lipids and proteins) under the retina
- choroidal neovascularisation causes bleeding and swelling in the macula
Risk factors of AMD
smoking
age >60
female
HTN, HLD, obesity
What defines wet AMD
presence of neovascularisation
AMD causes ___ vision loss
central
mild distortion (wavy lines on Amsler chart) -> central blurring -> central scotoma
Treatment for AMD
1) Anti-vascular endothelial growth factor injections
- blocks development of new vessels and leakage from abnormal vessels
2) Argon laser photocoagulation
- destroy neovessels away from fovea
3) Photodynamic therapy
- injection of light sensitive drug into bloodstream, absorbed by abnormal blood vessels
- laser light shone into eye, activates drug and damaged vessels
