Vitamins: How We Know Which One Is Needed?

DEAR SIR ------------ How we know that our body needs more vitamins i think after 18 years age vitamins and minerals recovery is not possible. I have 2.5 numbers in my eyes.Is vitamin a,e are good for eyes? Which vitamins are good for hands? Do you think that vitamin e and a is a very good source to increase eye-light. THANK YOU