Dry eyes are most commonly caused by tears reducing, that is, glands in your eyelids produces tears which are much less than normal. Meanwhile, if glands in eyelids cannot produce quality tears, dry eyes may also occur. I seek deeply online and found that vitamin D is not likely to help dry eyes because vitamin D is good for proper muscle and nerve functioning, even help to fight bacteria and viruses. However, dry eyes is hardly to be caused by bacteria and viruses. Well, the best way to heal dry eyes is to call a doctor for help. If you wanna heal it through supplements, then doctor's advise are very important. My elder sister, a doctor, who said that salmon, walnuts and fish is good for individual dry eyes.