Vitamin A was discovered at the turn of the century.1 It is required for normal cellular growth and differentiation and has an important role in the visual process.2 The effects on the eye of vitamin A deficiency are often seen in developing countries. It occurs primarily in children of school age and is usually seen in association with other nutritional deficits, such as multiple vitamin deficiencies and protein calorie malnutrition (marasmus). Over 124 million children worldwide are estimated to be deficient in vitamin A.3 This deficiency causes between one and two million deaths annually among children aged 1-4 years3 and is the commonest cause of childhood blindness in the world; over five million children develop xerophthalmia annually, a quarter of a million or more becoming blind.

Sporadic cases of dietary vitamin A deficiency are rare in the Western world,4 5 but patients with abnormal metabolism can manifest signs and symptoms of vitamin deficiency. These secondary deficiencies can occur with drugs and after small bowel bypass surgery, chronic alcoholic pancreatitis, and severe liver disease. In severe liver disease there is reduced production of retinol binding protein, reduced amounts of zinc, and reduced storage of vitamin A esters in the liver.