Vitamin A deficiency with night blindness

**Definition:** Night blindness (poor adaptation to darkness) is generally the earliest manifestation of vitamin A deficiency. In mild cases, night blindness is apparent only after photic stress. Affected children no longer move around after dusk and prefer to sit in a secure corner, often unable to find their food or toys. Night blindness of recent onset in a preschool child is practically pathognomonic of vitamin A deficiency. All patients respond rapidly to therapy with vitamin A, usually within 48 hours.