Definition of Nyctanopia

Nyctanopia: Impaired vision in dim light and in the dark, due to impaired function of the rods in the retina. Nyctanopia is a classic finding with vitamin A deficiency. Also known as day sight, nocturnal amblyopia, and nyctalopia.

Source: MedTerms™ Medical Dictionary
http://www.medterms.com/script/main/art.asp?articlekey=6449
Last Editorial Review: 3/19/2012