Vitamin A deficiency is one of the most common vitamin deficiency syndromes, particularly in developing countries. In many such regions, it is the most common cause of blindness. In the United States, vitamin A deficiency is usually due to fat malabsorption syndromes or mineral oil laxative abuse and occurs most commonly in older adults and individuals of lower socioeconomic status.
Night blindness is the earliest symptom. Dryness of the conjunctiva (xerosis) and the development of small white patches on the conjunctiva (Bitot spots) are early signs. Ulceration and necrosis of the cornea (keratomalacia), perforation, endophthalmitis, and blindness are late manifestations. Xerosis and hyperkeratinization of the skin and loss of taste may also occur.
Abnormalities of dark adaptation are strongly suggestive of vitamin A deficiency. Serum levels below the normal range of 30–65 mg/dL are commonly seen in advanced deficiency.
Night blindness, poor wound healing, and other signs of early deficiency can be effectively treated with vitamin A 30,000 international units orally daily for 1 week. Advanced deficiency with corneal damage calls for administration of 20,000 international units/kg orally for at least 5 days. The potential antioxidant effects of beta-carotene can be achieved with supplements of 25,000–50,000 international units of beta-carotene.