Role of Vit. A
Vitamin A is the chromophore of rhodopsin (vertebrate photoreceptor molecule) used in low light levels. Rhodopsin is a complex of Vit. A and Opsin protein present in the retina.
Vitamin A is essential for the epithelial cells. In Vitamin A deficiency, mucus-secreting cells are replaced by keratin producing cells, leading to xerosis.
Glycoprotein synthesis requires Vitamin A. In severe Vitamin A deficiency, lack of glycoproteins may lead to corneal ulcers or liquefaction.