Optic neuritis is a broad term expressing inflammation, degeneration, or demyelination of the optic nerve. It includes:
- papillitis or anterior optic neuritis - the intraocular portion of the nerve is affected, and the optic disc is swollen
- retrobulbar neuritis - optic neuritis in which the disc is not swollen
- neuroretinitis - optic disc and adjacent temporal retina are affected
The disc changes in papilloedema may closely resemble those of papillitis but visual acuity is reduced markedly in papillitis but not in papilloedema.