Rather than relating dry eyes to veganism, you need to think about foods, or supplements that you have started that you never had before.
It's not from giving up animal products.
It may be something added that is causing an allergic reaction.
Allergies can develop at any time. I know many adults who complain of seasonal allergies who never experienced them before. This could happen with anything.
Yeah sorry. I read it too fast the first time and missed the A part. It seems like it's really rare to be deficient in Vitamin A. I hope the doctor can give you more answers but until then I think you should treat yourself to some pumpkin pie!! Pumpkin is really high in Vitamin A and delicious as well.
Not eating enough calories and good fats can cause overall dryness. Also supplemental lecithin can help for skin and soft tissues. If you are low in Vitamin A, try juicing carrots or carrot juice everyday to get your fill of beta-carotene (which converts to vitamin A in the body).