I don't think your eyes get worse from looking at the screen. You will get tired but the eyes getting bad is something that would have happened anyway.
http://www.intelihealth.com/IH/ihtIH/WSIHW000/28067/28122/193064.html?d=dmtContent
http://www.stlukeseye.com/Conditions/ComputerVisionSyndrome.asp
http://www.intelihealth.com/IH/ihtIH/WSIHW000/28067/28122/193064.html?d=dmtContent
http://www.stlukeseye.com/Conditions/ComputerVisionSyndrome.asp