The swinging flashlight test in a patient with a right relative afferent pupillary defect (RAPD) shows:

• A Both pupils dilate when light shines in the right eye and constrict when light shines in the left eye ✓
• B The right pupil constricts briskly and the left does not
• C No change in pupil size regardless of which eye is illuminated
• D Paradoxical dilation of the right pupil during direct illumination when compared with consensual response

Explanation

In a right RAPD (Marcus Gunn pupil), the afferent limb of the pupillary reflex is reduced on the right side (optic nerve or extensive retinal lesion). Both pupils constrict more when light shines in the normal left eye and both pupils paradoxically dilate (or constrict less) when light quickly swings to the right eye — because the right eye sends a weaker afferent signal. Option D refers to the isolated right pupil, which appears to dilate relative to the stronger consensual constriction when light was in the left eye, but the full description is bilateral dilation when light is in the right eye.

Reference: Khurana Comprehensive Ophthalmology, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.