reading from the screen?

Probably many in the Habré are reading at computers, laptops, communicators, etc. Unfortunately, not many people, including me, know how to do it correctly. I want to ask who can deal with these issues, but I really do not want to wear glasses in a few years. I mean what kind of contrast, brightness, font size, background, etc. It is better to put that would cause the least possible harm to the eyes. Search not something sensible unfortunately did not give. Any material on this topic is welcome. Thank you in advance.