?:definition
|
-
Optic nerve transmits impulses generated by retinal photoreceptors to the brain. Damage anywhere along the optic nerve or to visual areas of brain can result in loss of vision. No overall definition for optic nerve disorders; SMQ focuses on optic neuropathy, optic neuritis (inflammation), and papilledema (swelling of optic nerve). Causes of optic neuropathy: toxins, including lead, methanol, ethylene glycol, tobacco or arsenic; compromised blood supply; nutritional deficiencies, especially vitamin B12; drugs, including chloramphenicol, isoniazid, ethambutol or digoxin. Loss of vision may be rapid (minutes or hours) or gradual over 2-7 days. One or both eyes can be affected, depending on cause. Vision can range from almost normal to complete blindness. Both eyes usually affected in optic neuropathy due to toxins or nutritional deficiency. Small area of vision loss at center of visual field slowly enlarges and can progress to complete blindness.
|