Effects of vitamin A deficiency on the ocular surface.

Vitamin A deficiency remains an important cause of ocular morbidity among patients with chronic liver disease and lipid malabsorption, and is a major cause of blindness in developing countries. Early ocular surface changes include keratinization of the conjunctiva and development of superficial punctate keratopathy. More severe deficiency results in corneal keratinization, ulceration, and necrosis. Vitamin A is necessary for normal differentiation of nonsquamous epithelium; keratinization is a direct consequence of its deficiency. Exposure exacerbates the process and surface phenomena, especially localized drying from loss of mucus-secreting goblet cells, reduced aqueous tear production, and irregularities of the keratinized surface may all contribute to stromal melting, which can occur in the absence of inflammatory infiltration or bacterial invasion. Surface abnormalities respond rapidly to systemic vitamin A. Significantly, corneal changes disappear long before the reappearance of goblet cells. Inflammation sometimes masks or reverses the xerotic process.