vitamin a deficiency

Vitamin A deficiency (VAD) or hypovitaminosis A is a lack of vitamin A in blood and tissues. It is common in poorer countries, especially among children and women of reproductive age, but is rarely seen in more developed countries. Nyctalopia (night blindness) is one of the first signs of VAD. Xerophthalmia, keratomalacia, and complete blindness can also occur since vitamin A has a major role in phototransduction. The three forms of vitamin A include retinols, beta-carotenes, and provitamin A carotenoids.Vitamin ...