Is a Markus Gunn pupil ALWAYS associated with central retinal artery occlusion?
(also known as a relative afferent pupillary defect) describes the finding during the swinging-flashlight test whereupon the patient’s pupil dilates instead of constricting when the light swings from the unaffected “good” eye to the affected “bad” eye. Upon shining the light into the “good” eye, both pupils will constrict. However, when the light moves to the “bad” eye, the light will not be perceived and both pupils will dilate as if there was no light at all. It is also considered lack of a consensual reflex in the affected eye, showing optic nerve damage in which the sensory or afferent stimulus sent to the brainstem is reduced. Severe retinal disease may also yield a Marcus Gunn pupil.
