Neuro10 Eye Flashcards
Retinitis
Retinal necrosis + edema leads to atrophic scar.
Iritis
Systemic inflammation.
Near vision
Ciliary muscle contracts (zonular fibers relax then lens relaxes which then becomes more convex) .
Distant vision
Ciliary muscle relaxes (lens flattens).
Aging
Sclerosis and decreased elasticity cause presbyopia (no near vision) due to change in lens shape.
Retinal artery occlusion
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.
Glaucoma
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
Cataract
Painless, bilateral opacification of lens leads to decrease in vision. Risk factors: age, smoking, EtOH, sunlight, classic galactosemia, galactokinase deficiency, diabetes (sorbitol), trauma, infection.
Papilledema
Increase in intracranial pressure leads to elevated optic disk with blurred margins, bigger blind spot (can be
seen in hydrocephalus) .
CN VI
innervates the Lateral Rectus
CN IV
innervates the Superior Oblique
The superior oblique abducts, intorts, and
depresses while adducted
CN III
innervates the Rest
The “chemical formula” LR6S04R3
CN III damage
eye looks clown and out; ptosis, pupillary dilation, loss of accommodation
CN IV damage
eye drifts upward causing vertical diplopia (problems reading newspaper or going down stairs)
CN VI damage
medially directed eye
Testing extraocular muscles
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.
Pupillary control
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.
Pupillary light reflex
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.
Retinal detachment
Separation of neurosensory layer of retina from pigment epithelium leads to degeneration of
photoreceptors leads to vision loss. May be 2° to trauma, diabetes.
Age-related macular degeneration (ARMD)
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.
Internuclear ophthalmoplegia (MLF syndrome)
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.
