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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


causes of pathologic anisocoria

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).


PSNS and SNS innervation of iris

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


parasympathetic dysfunction of eye

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.


sympathetic dysfunction of eye

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.


How do you determine which pupil is abnormal?

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


Horner syndrome

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)


Horner syndrome- orders

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)


Tonic pupil - cause, anisocoria, response to light

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.


Disease that causes tonic pupil



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

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


visual pathway

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



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.


do visual field defects cross vertical or horizontal meridians



Are visual field defects homonymous

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


optic nerve dysfunction symptoms

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


optic nerve dysfunction exam

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


what is an afferent pupillary defect

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


How are afferent pupillary defects detected

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).


color of healthy vs unhealthy optic nerve

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


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

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


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

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


ocular misalignment symptoms and causes

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


diplopia- questions to ask

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



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


oscillopsia- causes



types of nystagmus

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


downbeat nystagmus- cause

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