How does vitamin A deficiency affect the eyes?

Question

What will be an ideal response?

Answer 1

Night blindness is one of the first detectable signs of vitamin A deficiency and permits early diagnosis. In night blindness, the person loses the ability to recover promptly from the temporary blinding that follows a flash of bright light at night or to see after dark. In many parts of the world, after the sun goes down, vitamin A-deficient people become night-blind. They often cling to others or sit still, afraid that they may trip and fall or lose their way if they try to walk alone. Treatment with vitamin A rapidly corrects night blindness.
Beyond night blindness is total blindness—failure to see at all. Night blindness is caused by a lack of vitamin A at the back of the eye, the retina; total blindness is caused by a lack of vitamin A at the front of the eye, the cornea. Severe vitamin A deficiency is the leading cause of preventable blindness in the world, causing as many as half a million children to lose their sight each year; an estimated half of them die within a year of losing their sight. Blindness due to vitamin A deficiency, known as xerophthalmia, develops in stages. At first, the cornea becomes dry and hard because of inadequate mucus production—a condition known as xerosis. Then xerosis quickly progresses to keratomalacia, the softening of the cornea that leads to irreversible blindness. For this reason, prompt correction of vitamin A deficiency is essential to preserving eyesight.