Medical Definition of Sight, day
Sight, day: 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 finding 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 nyctalopia.
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