It is sad what is happening to your friend, but he will be able to deal with it once the issue is over, because he simply has a strong personality.
I worry about my eyesight, working so many hours on the computer and cell phone makes my vision immensely fatigued. I may have to give it all up, and it hurts, but we will have to find ways to fill that void.
Losing one's eyesight would be a terrible thing, maybe you could limit your screen time?