moon blindness

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Recurrent inflammation of a horse's eyes, often resulting in eventual blindness.

from The Century Dictionary.

• noun Same as moon-blink.
• noun An eye-disease of the horse, scientifically known as periodic ophthalmia, the cause of which is unknown. One attack is followed at regular intervals by others which finally produce total blindness in one or both eyes.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A chronic equine inflammatory eye disease.
• noun The optic condition night blindess: reduced eyesight in faint light.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun recurrent eye inflammation in horses; sometimes resulting in blindness
• noun inability to see clearly in dim light; due to a deficiency of vitamin A or to a retinal disorder