Do you know Wikipedia? There are lots of information on this website. It can provide all kinds of information that related to all fields of our life. I suggest you to have a look on it. Google can guide us to find some useful information online too. If you really don't know how to search on the internet, I suggest you to go to a book shop. There are many books about eye health. You just need to choose one of them and then you can have a good understanding of eye health. But if you want to know more, you can buy all kinds of books that talk about eye health. I often read books in our library becasue I don't want to buy books.