Vitamin D will affect your eyesight when you lack it. Vitamin is very close to our eye health. When you lack Vitamin D, it will cause cataract, parenchymatous keratitis, corneal ulcer, vesicular keratitis, blepharospasm and so on. What is more, if you are just a kid, you may have high myopia. So in order to avoid this happening, what you should do is to supply your body with enough vitamin D via different ways such as eating more milk, sea food, vegetables. But you should be careful because if you have too much vitamin D, it will do harm to your eyesight as well. So take care of yourself.