Deficiency of which of the following vitamins is associated with progressive keratinization of the cornea?

Vitamin A deficiency is the most impoant preventable cause of blindness. The earliest sign of deficiency is a loss of sensitivity to green light-followed by impairment to adapt to dim light-then night blindness (inability to see in the dark) More prolonged deficiency leads to xerophthalmia: keratinization of the cornea, and blindness