I'm 29 and I wear contacts, even though glasses are better for computer work. I have a slight astigmatism in my left eye; so slight that it can't be corrected by contacts. As such, it strains my eyes to read tiny text. So what did I do? I bumped up my font size.
Let's use HN as an example. I'm on a 13" MacBook Air with a screen resolution of 1440x900. In Chrome I hit Command-Shift-+ four to five times to make the text comfortably readable. In Terminal, I use Anonymous Pro at 16-22 pt. I often use OS X's Ctrl-Zoom feature to make things bigger.
I use F.lux to change the white point all the way to tungsten (2700K) at night. Since I was a kid I constantly focus through objects towards the horizon to relax my muscles.
I do all of these things to help my eyes, because I strain them all day long looking at screens. And I'm still in my twenties!
So do yourself and your eyes a favor and make your text gigantic.