Pupil Examination

Assessment of pupil size, shape, and reactions that can reveal important information about the visual and nervous system.

The pupil examination is a crucial part of the neuro-ophthalmic evaluation. Pupils respond to light and near focus, and abnormalities can indicate optic nerve problems, brain lesions, or autonomic dysfunction.

Key Takeaways

Pupils reveal nervous system function
Checks both direct and consensual responses
APD (Marcus Gunn pupil) indicates optic nerve problem
Size differences may indicate Horner or third nerve palsy
Simple but very informative examination

What's Tested

Size and Shape

Measured in millimeters
Compared between eyes
Noted in light and dark

Light Reaction

Direct response—same eye constricts
Consensual response—opposite eye constricts
Speed and completeness assessed

Near Response

Pupils constrict when focusing on near object
Tests different pathway than light

Swinging Flashlight Test

Alternating light between eyes
Detects relative afferent pupillary defect (RAPD/APD)

Key Findings

Relative Afferent Pupillary Defect (RAPD)

Also called Marcus Gunn pupil
Pupil dilates when light swings to affected eye
Indicates optic nerve problem on that side
Very important finding in neuro-ophthalmology

Horner Syndrome

Small pupil (miosis)
Ptosis
Anhidrosis (reduced sweating)
From sympathetic pathway disruption

Third Nerve Palsy

Large, poorly reactive pupil
Associated with ptosis, eye movement problems
Dilated pupil—consider aneurysm

Adie's Tonic Pupil

Large pupil, poor light reaction
Slow constriction to near
Benign condition

Pharmacologic Testing

Sometimes drops are used to help diagnose:

Dilute pilocarpine (Adie's)
Cocaine and apraclonidine (Horner's)
Hydroxyamphetamine (localize Horner's)

Medically Reviewed Content

This article meets our editorial standards

Written by:: Hashemi Eye Care Medical Team
Medically reviewed by:: Board-Certified Neuro-Ophthalmologist (MD, Neuro-Ophthalmology)
Last reviewed:: January 30, 2025

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