Abstract
Optic perineuritis is an inflammatory disorder involving the optic nerve sheath. It is currently considered as a part of idiopathic orbital inflammatory disease which also includes dacryoadenitis, orbital myositis, superior orbital fissure, and cavernous sinus syndrome (Tolosa hunt syndrome). As it is idiopathic, it is considered a diagnosis of exclusion. Another important differential is optic nerve lymphoma. Isolated optic nerve lymphoma associated with systemic involvement has been described in literature. We report a case that presented as third nerve palsy but later on developed central retinal vein occlusion and was ultimately diagnosed as primary gastric lymphoma of diffuse large B cell type.