Optic neuritis may be divided into papillitis (an inflamed optic nerve head visible with an ophthalmoscope) and retrobulbar optic neuritis, which includes mydriasis, absence of pupillary reflexes, and blindness without any ophthalmoscopic abnormalities. Flash electroretinography, combined with visual evoked potentials, and fluorescein angiography may be used to confirm optic neuritis. A CBC, blood chemistry profile, neurologic examination, radiology, and vitreous and CSF analyses may be indicated.
Papillitis is common in 1) granulomatous meningoencephalitis in dogs; 2) systemic viral, bacterial, and fungal infections in dogs, cats, horses, and cattle; and 3) trauma. It appears as a swollen optic nerve head with blurred margins, variable hemorrhages, and exudates. Peripapillary retinitis is often present and appears as a translucent to opaque retina adjacent to the optic disk. Therapy is directed at the underlying systemic disease. Systemic corticosteroids may be used for the optic neuritis. A positive response includes return of the pupillary reflexes and normal pupil size in several days, followed by vision a few days later.