Image Based Question-66032

Lesion at site (Bar) shown in the photograph causes which among the following ?

A. Wernicke’s hemianopic pupil.

B. Marcus Gunn pupil.

C. Marcus Gunn pupil.

D. None ofthe above.

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Correct Answer » A Explanation

Ans:A. Wernicke’s hemianopic pupil.

The site of lesion shown in the image is Optic Tract

ABNORMALITIES OF PUPILLARY REFLEXES

Amauratic light reflex

• Absence of light reflex on the affected side

• Absence of consensual light reflex on the normal side

• Lesions on the optic nerve or retinal on the affected side leading to complete blindness

Efferent pathway defect

• Absence of both direct & consensual light reflex on the affected side

• Near reflex is also absent on the affected side

• Presence of both direct and consensual light reflex on the normal side

• Efferent pathway defect → sphincter paralysis

• Causes: parasympatholytic drugs → atropine, homatropine, internal ophthalmoplegia, Ill N palsy

Wernicke’s hemianopic pupil

• Site of lesion — optic tract
• Light reflex is absent if the light is thrown

1. On the temporal half of the retina on the affected side
2. On the nasal half or the retina on the normal side

• Light reflex is present if the light thrown

1. On the nasal half of retina on the affected side
2. On the temporal half of retina on the normal side

Marcus Gunn pupil

• Otherwise known as Relative afferent pupillary defect (RAPD)

• A bright flash light is thrown to one eye and pupillary constriction is noted

• Then the light is quickly moved to the opposite eye and response noted

• This swinging to and fro of flash light is repeated several times

• Normally both pupils constrict equally and the pupil to which light is transferred remains tightly constricted

• In the presence of RAPD in one eye the affected pupil will dilate when the flash light is moved from the normal eye to the abnormal eye

• This response is called Marcus Gunn pupil which is the earliest feature of optic nerve deficiency

• Seen in optic neuritis, optic atrophy, CRAO, CRVO, RD

Argyll – Robertson pupil

• Accommodation Reflex Present , Pupillary Reflex Absent

• Commonly seen in neurosyphilis

• Also in multiple sclerosis, polio, encephalitis, diabetes mellitus

• Lesion at tectum (internuncial neurons b/w pretectal nucleus and EW nucleus at the level of pretectum)

• Pupils dilate poorly with mydriatics but constricts with serine

Holme Adie’s tonic pupil

• Light reflex absent

• Near reflex is slow and tonic

• Affected pupil is larger (anisocoria)

• Caused by postganglionic parasympathetic pupillomotor damage

• Usually unilateral, associated with absent knee jerk,

• Healthy young women, DM, amyloidosis, Shy-Drager syndrome

• Adie’s pupil constricts with 0.125% pilocarpine while normal pupil does not

• Pupil dilates with mydriatics