Optic neuritis describes any condition that causes inflammation of the optic nerve; it may be associated with demyelinating diseases, or infectious or inflammatory processes. It is also known as optic papillitis (when the head of the optic nerve is involved), neuroretinitis when there is a combined involvement of optic disc and surrounding retina in the macular area and retrobulbar neuritis (when the posterior part of the nerve is involved). [Source: Wikipedia 
]
