Vitamin A is a fat-soluble vitamin. Its physiological role is related to vision and maintenance of epithelial tissue. Prolonged deficiency of vitamin A leads to xerophthalmia (dry eye) for which the initial symptom is the night blindness. Deficiencies of vitamin A are known to be common in patients with primary biliary cirrhosis and chronic cholestatic liver diseases. Scientific research referring to therapeutic uses of vitamin A covers such areas as age-related macular degradation, retinitis pigmentosa, diabetes, HIV, measles, urinary tract infections and cancer. The prevention of bronchopulmonary dysplasia in newborn infants is an orphan designation of retinol.