Definition of Nyctalopia

Nyctalopia: Night blindness, impaired vision in dim light and in the dark, due to impaired function of certain specialized vision cells (the rods) in the retina.

"Nyctalopia" comes from the Greek "nyct" (night) + "aloas" (obscure or blind) + "opsis" (vision). Nyctalopia is also called day sight, nocturnal amblyopia, and nyctanopia.