Today we discussed a case of a 38 year old man with acute onset left eye vision loss with pain on eye movements and without eye redness. For an internist, the chief complaint of vision loss is often intimidating, but when we examine the facts with an anatomic framework, it becomes surprisingly simple.

Below is a diagram that includes our differential for acute, persistent, monocular vision loss. For completeness, retrochiasmal anatomy is included, but pathology occurring after the optic chiasm (in the optic tracts, Meyer loop, lateral geniculate nucleus, optic radiations) will cause bilateral homonymous hemianopsia, not monocular vision loss. Blindness occurring in the occipital lobe is termed cortical blindness and is bilateral and severe.

 When we consider pain with eye movements in our illness script, our differential narrows considerably to the following entitities:

Note that papilledema and GCA are not included in this chart because they include pain due to headaches, but not pain with eye movement.

Finally, when we consider that our patient’s eye was not injected, erythematous, or tearing, our differential narrows still further to endopthalmitis and optic neuritis. On fundoscopic exam, the clinical diagnosis of optic neuritis can be made if papillitis is seen without hypopyon, WBCs in the vitreous humor, or white mound-like lesions in the retina.