It does. Straining your eyes on a screen usually means you're focused on it for too long, and thus you are looking at the very same distance for a long time. The reason looking away for short periods of time helps is because it helps change t he distance of focus, which in turn helps keep the elasticity of the cristalline lens. This isn't the only cause, but it helps develop a basic form of myopia, and directly helps develop, along with age hardening and weakening the cristalline lens, presbyopia.
I did use a little wiki to get my terms right, but biology class did actually teach me something
dang