neuroophthalmology

Question 1

anisocoria

Answer 1

a difference in the size between a person’s pupils and size is measured using pupillary diameter. <1.0mm difference can be normal. Does NOT cause vision loss

Question 2

causes of pathologic anisocoria

Answer 2

efferent nervous system disturbance to the innervation of the muscles of the iris or is the result of local iris injury/damage. When sympathetic or parasympathetic dysfunction in the innervation of the pupil occurs, anisocoria is nearly always present (even when the dysfunction is bilateral owing to the lack of “perfectly symmetric” dysfunction).

Question 3

PSNS and SNS innervation of iris

Answer 3

The sphincter muscle of the iris is parasympathetically innervated and when it contracts, it results in a smaller pupil. The radial muscle of the iris is sympathetically innervated and when it contracts, it results in a larger pupil

Question 4

parasympathetic dysfunction of eye

Answer 4

results in a mydriatic pupil that is poorly responsive to light and the anisocoria that results will be greater in the light than in the dark.

Question 5

sympathetic dysfunction of eye

Answer 5

results in a miotic pupil that is poorly responsive to the dark. Thus, when sympathetic dysfunction occurs, the anisocoria will be greater in the dark than in the light.

Question 6

How do you determine which pupil is abnormal?

Answer 6

If the anisocoria is greater in dark and both pupils have a normal light response, then the smaller pupil is the abnormal pupil, and this finding is likely due to sympathetic dysfunction. If the anisocoria is greater in the light and the larger pupil has a poor response to light, then the larger pupil is the abnormal pupil

Question 7

Horner syndrome

Answer 7

disruption of sympathetic fibers resulting in ptosis, miosis, anhidrosis. Anisocoria greater in dark, normal pupillary response to light, and dilation lag of the miotic pupil (i.e. the pupil will take longer to dilate when going from light to dark)

Question 8

Horner syndrome- orders

Answer 8

order” is used to indicate which neuron in the three neuron pathway is affected. Level of brain stem (1st order) or spinal cord/lung (2nd order) or carotid/ cavernous sinus (3rd order)

Question 9

Tonic pupil - cause, anisocoria, response to light

Answer 9

Disruption of parasympathetic fibers at and beyond ciliary ganglion. Typically, the anisocoria is greater in the light; the large (abnormal). pupil will have poor response to light and segmental constriction to light will be present (segmental palsy). Constriction occurs better with focusing on near target than with light stimulus.

Question 10

Disease that causes tonic pupil

Answer 10

diabetes

Question 11

Why is there better response to near focus than light in tonic pupil

Answer 11

there is 30 to1 near responsive neurons to light -responsive neurons allowing a better chance for re-innervation to come from near responsive neurons

Question 12

visual pathway

Answer 12

optic nerve > chiasm > optic tract > lateral geniculate nucleus in thalamus > optic radiations >occipital cortex

Question 13

retinotopy

Answer 13

correspondence of the visual field defect to a given lesion location in the retina. Retinotopy is maintained throughout the visual pathways including within the optic nerve, chiasm, optic tract, lateral geniculate nucleus, optic radiations, and occipital cortex.

Question 14

do visual field defects cross vertical or horizontal meridians

Answer 14

no

Question 15

Are visual field defects homonymous

Answer 15

yes- they inolve the same area of the visual field in each eye

Question 16

optic nerve dysfunction symptoms

Answer 16

Monocular vision loss (blurred, missing,dim), Decreased brightness or color vision impaired

Question 17

optic nerve dysfunction exam

Answer 17

Vision loss (acuity, field, or both), Afferent Pupillary Defect (APD), Color vision loss, Abnormal optic nerve

Question 18

what is an afferent pupillary defect

Answer 18

aka Marcus Gunn pupil- always be present in unilateral or asymmetric optic nerve dysfunction.

Question 19

How are afferent pupillary defects detected

Answer 19

swinging flashlight- The light is first shined in one eye and then swung back and forth between the pupils at equal speed. If one of the pupils dilates each time the light is shined in that eye after swinging from the other eye, then afferent dysfunction is present (there is a relative decrease in the light detected from one eye compared to the other).

Question 20

color of healthy vs unhealthy optic nerve

Answer 20

A healthy optic nerve is typically orange/yellow and nerve loss will result in a white or pale nerve.

Question 21

for optic neuritis: describe vision loss, pain, age, optic nerve appearance and recovery

Answer 21

Visual acuity (VA) loss is almost always present and Visual Field (VF) usually central.  Paiin Common – and occurs with eye movements (~95%). Younger.  2/3 of patients have normal optic nerve appearance at onset
-pallor develops later. Usually near complete recovery by 6 weeks – 10 week

Question 22

For anterior ischemic optic neuropathy: describe vision loss, pain, age, optic nerve appearance and recovery

Answer 22

visual acuity loss can be present and Visula Field loss is typically altitudinal or arcuate . Pain is Rare. Older. Edema with hemorrhages -pallor develops later. Minimal recovery

Question 23

ocular misalignment symptoms and causes

Answer 23

binocular diplopia (meaning that the diplopia is present only when both eyes are open and goes away when either eye is closed). Causes include cranial nerve nuclei, cranial nerve fascicles, neuromuscular junction (e.g. myasthenia gravis), or extraocular muscle weakness

Question 24

diplopia- questions to ask

Answer 24

binocular? Horizontal vs vertical? Worse with any position of gaze? Worse at near or far viewing?

Question 25

oscillopsia

Answer 25

the appearance of movement of the visual world due to an eye movement disturbance.

Question 26

oscillopsia- causes

Answer 26

nystagmus

Question 27

types of nystagmus

Answer 27

pendular (slow-slow phases), jerk (fast-slow phases), or mixed (slow-slow as well fast-slow phases).

Question 28

downbeat nystagmus- cause

Answer 28

cervical-medullary junction damage. The cause is due to compression of the cerebellar flocculus due to an Arnold-Chiari malformation (i.e. presence of the cerebellum below the foramen magnum). The flocculus normally inhibits the anterior (and not the posterior) semicircular canal connections. The anterior semicircular canals normally stimulate the eyes to move upward. When the anterior semicircular canals are disinhibited, the eyes will drift up and then a fast “corrective” phase downward occurs