Day sight: Night blindness. Listed in medical dictionaries under "Nyctalopia" from the Greek "nyct' (night) + "aloas" (obscure or blind) + "opsis" (vision), the condition involves impaired vision in dim light and in the dark (but normal sight in bright light), due to impaired function of specific vision cells (the "rods") in the retina. Day sight (night blindness) is a classic symptom resulting from deficiency of vitamin A. It was discovered by the English physician William Heberden (1710-1801) who described other medical disorders of importance including angina pectoris (chest pain that is often severe and crushing, due to an inadequate supply of oxygen to the heart muscle) and osteoarthritis of the small joints with nodules (Heberden's nodes) in and about the last joint of the finger. Day sight (night blindness) is also called nocturnal amblyopia and nyctanopia.