The Marcus Gunn pupil is a<unk>  indicating a decreased<unk>  response to light in the affected eye. In the swinging flashlight test, a light is alternately shone into the left and right eyes. A normal response would be equal constriction of both pupils, regardless of which eye the light is directed at. This indicates an intact direct and consensual<unk>  light reflex. When the test is performed in an eye with an<unk><unk><unk> , light directed in the affected eye will cause only mild constriction of both pupils (due to decreased response to light from the<unk><unk> , while light in the unaffected eye will cause a normal constriction of both pupils (due to an intact<unk>  path, and an intact consensual<unk>  reflex). Thus, light shone in the affected eye will produce less<unk>  constriction than light shone in the unaffected eye. Anisocoria is absent. A Marcus Gunn pupil is seen, among other conditions, in optic neuritis. It is also common in retrobulbar optic neuritis due to multiple sclerosis but only for 3–4 weeks, until the visual acuity begins to improve in 1–2 weeks and may return to normal. A total CN II lesion, in which the affected eye perceives no light, is very similar to a Marcus Gunn pupil; to distinguish them, in a CNII total lesion shining the light in the affected eye produces zero dilation nor constriction.
Relative afferent pupillary defect
Mechanical anisocoria
Physiological anisocoria
Persistent pupillary membrane
Ocular dysmetria
Nephroptosis
Scintillating scotoma
Optic disc pallor