I suppose that depends on a few things. Long term computer use can lead to you becoming more short-sighted. My optician told me it's because your eyes learn to focus on things as far away as your monitor and get less good at focusing at things that are further away. Apparently (I really don't know for sure) that's why it's very hard to realize you need new glasses just looking at your PC.
However - It takes extremely hardcore computer use to even potentially see this happen. My guy brought it up to me because my day job put me at a PC for 8 hours a day, and my down-time I spend writing and playing PC games. I do EVERYTHING, all day every day, through a pc. Also, I have always had glasses ever since I was little and we didn't have a...