Amblyopia refers to blindness so nocturnal amblyopia is, literally, 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 due to impaired function of specific vision cells (namely, the rods) in the retina. Night blindness, a classic finding in vitamin A deficiency, was discovered by the English physician William Heberden (1710-1801). (Heberden also described other medical disorders of importance including angina (chest pain that is often severe and crushing, due to an inadequate supply of oxygen to the heart muscle) and Heberden's nodes, bumps around the small joints due to osteoarthritis.) Night blindness (nyctalopia) is also called day sight and nyctanopia.