Isocoria with Normal Pupil Size

 Relative Afferent Pupillary Defect

Causes: 

Unilateral sensory disorder such as retinal detachment, neuritis ofthe optic nerve, atrophy of the optic nerve, or retinal vascular occlusion.

Diagnostic considerations:

❖ Direct light reflex is decreased or absent (relative afferent pupillary defect) in the affected eye.

❖The consensual light reflex in the affected eye is weak or absent but normal in the unaffected eye.

❖The swinging flashlight test reveals dilation in the affected eye when illuminated (Marcus Gunn pupil) or reduced constriction and earlier dila-tion in the presence of lesser lesions (afferent pupillary defect).

❖Near reflex is normal.

❖Unilaterally reduced visual acuity and/or field of vision.

Unilateral blindness (afferent defect) does not produce anisocoria.

Bilateral Afferent Pupillary Defect

Causes: 

Bilateral sensory disorder such as maculopathy or atrophy of theoptic nerve.

Diagnostic considerations:

❖Delayed direct and consensual light reflexes.

❖The swinging flashlight test produces identical results in both eyes (where disorder affects both sides equally).

❖Near reflex is normal.

❖Bilaterally reduced visual acuity and/or field of vision.

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