Eye conditions

Question 1

Common eye conditions:

Refractory

Answer 1

Hyperopia: light focused behind retina (aging)
Myopia: light focused in front of retina (young=ME)
Astigmatism: abn curvature

Accommodation: focusing near objects -> ciliary muscles tighten -> zonular fibers relax -> lens become more convex
Occurs with convergence and miosis

Presbyopia: decreased change in focusing ability during accommodation due to sclerosis and decreased elasticity

Question 2

Uveitis

Answer 2

Inflammation of uveal coat (iris, ciliary body, choroid)

Associated with systemic dz (sarcoid, RA, juvenile idiopathic arthritis, TB, HLA B27)

Question 3

Retinitis

Answer 3

Retinal edema and necrosis leading to scar
Often viral (CMV, HSV, HZV) associated with immunosup

Question 4

Central retinal artery occlusion

Answer 4

Acute, painless monocular vision loss

Retina whitening with cherry red spot.

Question 5

Control of aqueous humor pathway

Answer 5

Iris dilator: alpha 1
Sphincter: M3
Ciliary epithelium: beta2 (produces aqueous humor)
Ciliary muscle: M

Canal of Schlemm collects aqueous humor from trabecular meshwork.

Trabecular meshwork collects aqueous humor that flows from anterior chamber.

Question 6

Glaucoma: open angle/wide

Answer 6

Peripheral then central vision loss usually with high IOP,
Optic disc atrophy with cupping
Associated with age, AA race, fam hx, high IOP
Painless, more common in US

Primary cause: unclear
Secondary cause: uveitis, trauam steroid, and vasoproliferative retinopathy that can block or reduce outflow at the trabecular meshwork

Question 7

Glaucoma: closed/narrow angle

Answer 7

Enlargement or forward movement against central iris leads to obstruction of normal aqueous flow through pupil,
fluid builds up behind iris, pushing peripheral iris against cornea and impeding flow through the trabecular meshwork

Chronic closure: often asymptomatic with damage to optic nerve and peripheral vision

Acute closure: true ophthalmic emergency, increased IOP pushes iris forward -> angle closes abruptly. Very painful, sudden vision loss, halos around the light, rockhard eye, frontal headache.
-Do not give epi because of its mydriatic effect.

Question 8

Cataract

Answer 8

Painless, often bilateral opacification of lens
Decrease in vision

Risk factors: age, smoking, ETOH, excessive sunlight, prolonged steroid, classic galactosemia, galactokinase deficiency, diabetes(sorbitol), trauma, and infection

Question 9

Papilledema

Answer 9

Optic disc swelling (usually bilateral) due to increased ICP (e.g. 2nd to mass effect).

Enlarged blind spot and elevated optic disc with blurred margins seen on fundoscopic exam.

Question 10

EOM lesion: CN 3

Answer 10

Eyes look down and out:

ptosis, pupillary dilation, loss of accommodation

Question 11

EOM lesion: CN 4

Answer 11

Eyes look upward, particularly with contralateral gaze and ipsilateral head til

Problem going downstairs

Superior oblique abducts, intorts, and depresses while adducted.

Question 12

EOM lesion: CN 6

Answer 12

Medially directed eye that cannot abduct

Question 13

Testing EOM

Answer 13

IOU: to test Inferior Oblique, have patients look UP
SO: have patients depressed eye when adducted.

Question 14

Pupillary control: miosis

Answer 14

Miosis (constriction, parasympathetic)
1st neuron: Edinger-Westphal nucleus to ciliary ganglion via CN 3
2nd neuron: short ciliary nerves to pupillary sphincter muscles.

Question 15

Pupillary control: mydriasis

Answer 15

Mydriasis (dilation, sympathetic)
1st neuron: hypothalamus to ciliospinal center of Budge (CN8-T2)
2nd neuron: exit at T1 to superior cervical ganglion (travel along cervical sympathetic chain near lung apex, subclavian vessels)
3rd neuron: plexus along internal carotid, through cavernous sinus, enters orbi as long ciliary nerve to pupillary dilator muscles.

Question 16

Pupillary light reflex

Answer 16

Light enters retina via CNII to pretecta nuclei in midbrain, activates bilteral Edinger-Westphal nuclei;
pupils contract bilaterally (consensual reflex)

Results: illumination of one eye, constricts both pupils

Marcus Gunn pupil: afferent pupillary defect, reduced bilateral pupillary constriction when light is shone in affected eye.

Question 17

CN3

Answer 17

Both motor (central) and parasym (peripheral)

Motor output: affected primarily by vascular disease (diabetes; glucose-> sorbitol) due to low diffusion of oxygen and nutrients to the interior fibers from compromised vasculature that resides on outsdie of nerve
“Sign: ptosis and down and out”

Parasympathetic output: fibers on the periphery are 1st affected by compression (PComm aneurysm, uncal herniation)
“Sign: diminished or absent pupillary light reflex, blown pupil”

Question 18

Retinal detachment

Answer 18

Separation of retina from outermost pigmented epithelium
(normally shields excessive light, supports retina)
Degeneration of photoreceptors -> vision loss
May be 2/2 retinal breaks, diabetic traction, inflam effusions

Breaks more common with high myopia and often preceded by posterior vitreous detachment (flashes and floaters), and eventually monocular vision loss like a curtain drawn. Surgical emergency.

Question 19

Age-related macular degeneration

Answer 19

Degeneration of macula (central area of retina)
Causes distortion (metamorphosia) and eventual loss of central vision (scotomas)

1) Dry (nonexudative, >80%) deposition of yellow extracellular material beneth retinal pigment epithelium (drusen) with gradual loss of vision.
Prevent progression with multivitamin and antioxidant supplements.

2) Wet (exudative, 10-15%) rapid loss of vision due to bleeding, 2/2 chorodial neovascularization
Treat with anti VEGF or laser.

Question 20

Visual field defect

Answer 20

Optic nerve: ranopsia
Optic chaism: bitemporal hemianopsia
Optic tract: homonymous hemianopsia
Meyer’s loop (temoral): upper quadratic anopia (MCA)
Dorsal optic radiation (parietal lobe): lower quadratic anopia (MCA)
PCA infarct: hemianopsia with macular sparing.

Question 21

Internuclear ophthalmoplegia (MLF)

Answer 21

Medial longitudinal fasciculus: pair of tracts that allows for crosstalk between CN 6 and CN 3 nuclei.

Coordinates both eyes to move in same horizontal direction.

Highly myelinated (must communicate quickly so eyes move quickly. Lesions seen in patients MS.

Lesion: when CN 6 ncuelus activates ipsilateral lateral rectus, contralateral CN3 nucleus does not stimulate medial rectus to fire.

Therefore, abducting eye gets nystagmus (CN6 overfires to stimuates CN3), Convergence IS normal.