The authors present the differential diagnosis of inflammatory optic neuritis (ON) to include multiple sclerosis, infectious optic neuritis, systemic disease and neuromyelitis optica (NMO). The features of ON for the varying aetiologies are detailed including incidence and overlap. In acute demyelinating ON, patients typically present with progressive unilateral visual loss of variable severity, usually associated with pain. Optic neuritis due to infection more frequently corresponds to neuroretinitis rather than typical ON. ON due to NMO is often more severe and bilateral in nature. ON due to systemic disease has a low incidence reported in reviewed literature. Differentiation between causes is essential for therapeutic and management decisions to be made. A study was performed on 62 patients with relapsing ON and an eight year follow-up period reported. In this group of patients with recurrent ON, two groups had a poor prognosis (high risk of NMO and chronic relapsing inflammatory ON) that may be treated early with immunosuppressive treatments.