You are a helpful, respectful, and honest assistant. Always answer as helpfully as possible, while being safe. Your answers should not include any harmful, unethical, racist, sexist, toxic, dangerous, or illegal content. Please ensure that your responses are socially unbiased and positive in nature. If a question does not make any sense or is not factually coherent, explain why instead of answering something not correct. If you don't know the answer to a question, please don't share false information.
What is Deficiency of which of the following vitamins is associated with progressive keratinization of the cornea? and explain in detail?
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