Neuro10 Eye

Question 1

Retinitis

Answer 1

Retinal necrosis + edema leads to atrophic scar.

Question 2

Iritis

Answer 2

Systemic inflammation.

Question 3

Near vision

Answer 3

Ciliary muscle contracts (zonular fibers relax then lens relaxes which then becomes more convex) .

Question 4

Distant vision

Answer 4

Ciliary muscle relaxes (lens flattens).

Question 5

Aging

Answer 5

Sclerosis and decreased elasticity cause presbyopia (no near vision) due to change in lens shape.

Question 6

Retinal artery occlusion

Answer 6

Acute, painless monocular loss of vision; pale retina and cherry-red macula. Macula is much thinner than the surrounding retina so the choroid is more easily visualized through the macula.

Question 7

Glaucoma

Answer 7

Impaired flow of aqueous humor leads to increased intraocular pressure which then leads to optic disk atrophy with cupping.
Open/wide angle-obstructed outflow (e.g., canal of Schlemm); associated with myopia, increased age,
African-American race. More common, “silent,” painless.
Closed/narrow angle- obstruction of flow between iris and lens leads to pressure buildup behind iris.
Very painful, decreased vision, rock-hard eye, frontal headache. An ophthalmologic emergency. Do not give epinephrine.

Closed/narrow angle glaucoma refers to enlargement or forward movement of the lens against the central iris, pushing the peripheral iris against the cornea and blocking flow through the trabecular meshwork

Question 8

Cataract

Answer 8

Painless, bilateral opacification of lens leads to decrease in vision. Risk factors: age, smoking, EtOH, sunlight, classic galactosemia, galactokinase deficiency, diabetes (sorbitol), trauma, infection.

Question 9

Papilledema

Answer 9

Increase in intracranial pressure leads to elevated optic disk with blurred margins, bigger blind spot (can be
seen in hydrocephalus) .

Question 10

CN VI

Answer 10

innervates the Lateral Rectus

Question 11

CN IV

Answer 11

innervates the Superior Oblique

The superior oblique abducts, intorts, and
depresses while adducted

Question 12

CN III

Answer 12

innervates the Rest

The “chemical formula” LR6S04R3

Question 13

CN III damage

Answer 13

eye looks clown and out; ptosis, pupillary dilation, loss of accommodation

Question 14

CN IV damage

Answer 14

eye drifts upward causing vertical diplopia (problems reading newspaper or going down stairs)

Question 15

CN VI damage

Answer 15

medially directed eye

Question 16

Testing extraocular muscles

Answer 16

To test the function o f each muscle, have the patient look in the following directions (e.g., to test SO, have patient depress eye from adducted position)

IOU: to test Inferior Oblique, have patient look Up.

Question 17

Pupillary control

Answer 17

l . Constriction (miosis) - Pupillary sphincter muscle (aka circular muscle). Parasympathetic.
Innervation-CN III from Edinger-Westphal nucleus to the ciliary ganglion.
2. Dilation (myDriasis) -radial muscle (aka pupillary dilator muscle), sympathetic. Innervation Tl preganglionic sympathetic to superior cervical ganglion to postganglionic sympathetic to long ciliary nerve.

Question 18

Pupillary light reflex

Answer 18

Light in either retina sends a signal via CN II to pretectal nuclei (dashed lines) in midbrain that activate bilateral Edinger-Westphal nuclei; pupils contract bilaterally (consensual reflex).
Result: illumination of 1 eye results in bilateral pupillary constriction.
Marcus Gunn pupil-afferent pupillary defect (e.g., due to optic nerve damage or retinal
detachment) . Decreased bilateral pupillary constriction when light is shone in affected eye.

Question 19

Retinal detachment

Answer 19

Separation of neurosensory layer of retina from pigment epithelium leads to degeneration of
photoreceptors leads to vision loss. May be 2° to trauma, diabetes.

Question 20

Age-related macular degeneration (ARMD)

Answer 20

Degeneration of macula (central area of retina) . Causes loss of central vision (scotomas) . “Dry”/ atrophic ARMD is slow, due to fat deposits, and causes gradual J, in vision. “Wet” ARMD is rapid, due to neovascularization.

Question 21

Internuclear ophthalmoplegia (MLF syndrome)

Answer 21

Lesion in the medial longitudinal fasciculus (MLF) leads to medial rectus palsy on attempted lateral gaze. Nystagmus in abducting eye. Convergence is normal. Syndrome is seen in
many patients with multiple sclerosis.

MLF = MS .
When looking left, the left nucleus of CN VI fires, which contracts the left lateral rectus and stimulates the contralateral (right) nucleus of CN III via the right MLF to contract the right medial rectus.