Background: Optic neuritis is a frequent cause of vision loss encountered by ophthalmologists in the Caribbean. The diagnosis is made on clinical grounds. Optic neuritis can occur either in an isolated manner or, most often, as the first symptom of multiple sclerosis (MS) or neuromyelitisoptica (NMO). These 2 demyelinating disorders differ by many means, including treatment and prognosis. MS can cause severe long-term disability while NMO is a short-term sight- and life-threatening condition causing potential relapses, which may require plasma exchanges. Furthermore, disease-modifying therapies used in NMO are different from those used in MS, which can worsen the natural history of NMO. Early differential diagnosis of these diseases is thus crucial for preventing severe visual loss and disability.