Xerophthalmia is a severe drying of the eye surface caused by a malfunction of the tear glands. Also found in people with immune disorders, it occurs most commonly because of decreased intake or absorption of vitamin A. Symptoms include night blindness and eye irritation. In addition to the eyes being very dry, there is a loss of luster on their surface. At later stages, the corneas become soft, with increased opacity.
Rarely seen in industrialized countries, xerophthalmia remains the leading cause of childhood blindness in the developing world. Up to ten million cases occur among children every year due to a dietary deficiency of vitamin A, and 5 percent of these children become blind.
Xerophthalmia is treated with artificial eye moisturizers and vitamin A supplementation. In 1999 a genetically engineered form of rice was created that contains up to 20 percent beta-carotene, a rich source of vitamin A. It is hoped that this grain, known as golden rice, will alleviate much of the world's vitamin A deficiency. However, critics maintain that the volume of rice needed to reach the daily recommended amount of vitamin A is too excessive to be practical. In addition, lingering concerns about the safety of genetically engineered foods may affect its use.
National Institutes of Health Clinic Center. "Vitamin A and Carotenoids." Available from <www.cc.nih.gov>
Merck Manual. "Vitamin A Deficiency." Available from <www.merck.com/pubs/mmanual>