I'm becoming more and more interested in diet, and the carrots reference was a bit of a joke.  Well carrots contain lutein and beta carotein, and both are antioxidents that can improve eye health, but there is more to it than that. If you are sitting in front of a screen for long period, don't start at it solidly, but look out of a window frequently, and focus on trees and houses in the distance. Get up and walk around now and then to give yourself a break.