Disorder of Vision

Aqueous humor pathway

Made by ciliary body EP → travel through posterior chamber → enter anterior chamber → 90% enter trabecular meshwork → Canal of Schlemm → episcleral vss; 10% drain into uvea and sclera

Parts of accommodation

Lens accommodation by zonule tension/relaxation, miosis, convergence

Cellular eye layers

Outer = choroid → pigmented EP → rod and cone → Outer nuclear → outer plexiform → inner nuclear → inner plexiform → ganglion cell layer → nerve fiber layer → nearest to vitreous humor

Vascular supply of the occipital cortex

PCA from basilar supplies the medial part of occipital; MCA from ICA supplies the lateral part of occipital

Vascular supply of the eye

ICA clinoid → Opthalmic A → Central retinal that pierce and feed center of eye + posterior ciliary a → short is near optic disc, long supplies ciliary muscle

What part of the eye is spared when there is infarction of retinal supply

Foveola only

Pupillary light reflex pathway

Light enter optic nerve → signal branch out (one cross chiasm one doesn’t) → optic tract → synapse at pretectal area in LGN → Bilat projection into Edinger-Westphal → travel along CN III → synapse at ciliary ganglion → miosis

Mechanisms of reduced vision (non nerve)

Refractive area = light is not doing into retina

Media opacity = light is obstructed bc media is cloudy

Retina = photoreceptor and structures fail

What are refractive errors

Simple bad eyesight fixed with glasses

Myopia → light does not reach retina → fix w concave lens

Hyperopia → light extends past retina → fix w convex lens

Astigmatism → many light refractions → fix w circular lens

What is presbyopia

Impaired accommodation in older people from loss lens elasticity, change in lens curvature and lower ciliary muscle strength

What is pinguecula and pterygium

Fibrovascular growth of conjuctiva

• Pinguecula → does NOT involve limbus

• Pterygium → grows big enough to reach into cornea causes astigmatism

What is the difference between these two images

Lt → has not reached limbus = pinguecula → likely no vision problem

Rt → crosses limbus to cornea = pterygium → expect astigmatism

Causes of corneal ulcer and scar

Infection (HSV), SJS, Reiter, corneal edema/deposition, keratitis, glaucoma, trauma

What are cataracts

INCREASED opacity of the lens

What is the difference between these 3 types of cataracts

Lt → See orange center = senile nuclear

Middle → See white fibers in center with some clear area → Cortical

Rt → white fiber with NO clear area → Mature cortica

What is this

Fully opaque lens and brown deposits at the bottom of lens → Margagnian cataract

Component of glaucoma

Loss of retinal ganglion cell, cupping, visual field defect

What is glaucoma

Change in aqueous humor flow → eg flow of trabecular meshwork = lack of outflow into vss

What is the difference between primary and secondary open angle glaucoma

Primary (POAG) → more frequent in older and black people

Secondary (SOAG) → RBC/WBC etc block trabecular network → higher episcleral venous pressure

Signs of angle closure glaucoma

EMERGENCY → painful red eye, sudden vision loss, halo around light, headache, fixed dilate pupil, nausea vomiting

Types of uvea abnormalities

Keratic precipitate, hypopyon (cell that settle at the bottom), vitritis (blurred optic disc), neuroretinitis (cat scratch, see macular star)

What is diabetic retinopathy

Non proliferative DR → damaged capillary leak of blood/lipid/macular edema

Proliferative DR → chronic hypoxia → neovascular formation → retinal traction

What are the abnormalities found in DR

Green = hard exudate

Purple = microaneurysm

Blue = dot/blot hemorrhage

What is this

Blood in vitreous humor → rupture of ciliary/retinal vss

Seeing this with increased frequency is a sign of what

If you see floaters infrequently is benign → if increased is sign of vitreous detachment common in DM w neovascularization

Types if retinal detachment

- Rhegmatogenous retinal detachment (RRD): retinal breaks

- Tractional retinal detachment (TRD): DR

- Exudative retinal detachment: Uveitis, mass

What is hypertensive retinopathy

Chronic uncontrolled HTN → causes endothelial disruption, fibrinoid necrosis and retinal damage

What are all these signs

Signs of HYPERTENSIVE RETINOPATHY

Blue = Arterial narrowing

Red = Arteriovenous (AV) nicking

Pink = Cotton wool spots

Can also present with: Flame-shaped retinal hemorrhages, Microaneurysms, Optic nerve head swelling

What is central retinal artery occlusion (CRAO)

Acute painless monocular vision loss → see retinal WHITENING with CHERRY RED fovea

What is this

CRAO → white retina + cherry red fovea

What is BRAO

Occlusion of a BRANCH of central retina → whitening only in area that branch supplies

Diff these two images

Lt = CRAO → retina is white and general + cherry red fovea

Rt = BRAO → partial white retinal area

What is amaeurosis fugas

Sudden painless vision loss → curtain linked lasting a few seconds → completely back to normal → caused by TIA

What is this

Retinal vein occlusion → Lt is central (CRVO), Rt is branch (BRVO) → see hemorrhage and venous engorgement

What is age related macular degeneration (AMD)

May present with metamorphosia = loss of straight line and scotoma = loss of central vision

What is retinitis pigmentosa

Dystrophy of retina EP and photoreceptor → present as tunnel vision and nyctalopia = trouble seeing in dark

What is this

Green = optic disc pallor

Purple = vss attenuation

Blue = pigmentation with spicule shaped margins

Are all TRIAD of findings for Retinitis pigmentosa

What is leukocoria

Loss of red/orange reflection/glow → replaced with white/gray color found in congenital cataract and retinoblastoma

What is papilledema

High ICP → bilateral optic disc edema → transient visual obscure/bigger blind spot

What is ischemic optic neuropathy

AAION → caused by GCA and NAION

Lower flow to optic nerve head → altitudinal VFD

How to pre chiasmatic from chiasmatic and post chiasmatic lesions

Pre chiasmatic respect HORIZONTAL meridian

Rest respect VERTICAL meridian

Optic nerve lesion sign

Ipsilateral ANOPIA/blindness with positive RAPD/Marcus Gunn

Bitemporal hemianopia is caused by lesion to what area

Optic chiasm → compression from mass (pituitary macroadenoma/craniopharyngioma etc)

What is junctional scotoma

Distal optic nerve lesion and anterior chiasm → Wilbrand’s knee

LGN stroke signs

Lateral posterior choroidal → incomplete, incongruous homonymous

(horizontal) sectoranopia

Anterior choroidal → incomplete quadruple sectoranopia OR incomplete homonymous hemianopia with horizontal sparing

based on this visual field where is the lesion

Lt → Lateral posterior choroidal of LGN

Rt → Anterior choroidal of LGN

What is the difference between visual loss of Meyer and dorsal bundles

Meyers: In temporal lobe causes SUPERIOR quadrant loss from MCA infarct

Dorsal: In parietal lobe causes INFERIOR quadrant loss from PCA infarct

Why is the macular area spared in infarction

Dual supply by PCA and MCA → if either infarct the remaining artery still supply

What is monocular occipitotemporal crescent syndrome

Contralateral lesion of anterior occipital → controls the most PERIPHERAL part of field (60-90 degrees) → lesion causes loss of peripheral sight

PNS control of pupil

Causes CONSTRICTION → neuron at EWN go to ciliary ganglion through CN III → synapse at short ciliary nerve of sphincter pupillary muscle → miosis

Pathway of near pupillary reflex

Primary visual cortex → Supranuclear → Supraoculomotor area In midbrain → Oculomotor nucleus → MR → Convergence → EW nucleus → ciliary ganglion → Short ciliary n. Lens accommodation and miosis

What is this

Argyll Robertson pupil → PRETECTAL defect → No light reflex + spare accommodation

What is this

Adie’s tonic pupil → PSN ciliary ganglion damage → aberrant regeneration → poor light stimulus with better response to near object on affected eye

SNS control of pupil

DILATION → from hypothalamus and synapse at C8-T2 ciliospinal center → travel across lung apex → superior cervical ganglion synapse → plexus ascend ICA → travel by opthalmic artery

Horner syndrome triad

Miosis, anhidrosis, ptosis

Cause of CN III palsy

EOM problem + headache = PComm Aneurism

DM, HT, atherosclerosis

EOM problem + pupil problem = compressive lesion

What is MLF pathway

Frontal eye field → PPRF → abducen nucleus → LR movement → project to contralateral MLF → oculomotor nucleus → movement of MR

What is INO

Lesion of MLF → show abducting eye nystagmus to stimulate CN III; MG can mimic this

Cavernous sinus syndrome signs

• Unilateral ophthalmoplegia (cranial nerve III, IV, VI)

- Autonomic dysfunction (Horner syndrome) or

- Sensory CN V1 - CN V2 loss

Parts of the eye

Fibrous tunic: sclera and cornea

Vascular tunic/uvea: iris, ciliary body, choroid

Retina: pigmented and neural layer

Parts of the uvea

Iris → muscles dilatory and sphincter

Ciliary body → zonule suspensory ligaments

Choroid → brown pigmented cells that absorb light