Start by deciding whether the complaint is true visual loss or just blur, then determine whether it is monocular or binocular. That sequence keeps papilledema, optic neuritis, and retinal ischemia separated before the workup becomes unfocused.

Papilledema usually lacks an afferent pupillary defect and does not cause early severe visual loss; Optic neuritis often causes an afferent pupillary defect and marked visual loss; Central retinal artery occlusion is a major ischemic cause of acute monocular vision loss; Ocular ischemia and retinal vein occlusion remain important alternatives; Monocular versus binocular symptoms should guide the first diagnostic branch