What should I do to keep my vision the same and good?

Well, I’m just worried that reading too much will make my eyesight go bad. I’ve been reading a lot lately, due to schoolwork, and also books on investing…..
What are some things that I should do to keep my eyesight good and the same? After I read, sometimes my vision is temporarily blurry…. is that normal?

Also university will have a lot of reading involved as well, I fear getting glasses. Please give suggestions/ comments, but no negative ones! =]