When I first started my current job - back in 2003, a guy there who had been doing that sort of work on computer longer than me told me: You need to spend 10-15 minutes a day reading material from a printed source, as opposed to on a computer screen.. Reason being, DPi of printed source is much higher than computer screen, so only reading from computer screen is making your eyes lazy, or work harder, causing your vision to go to crap..
I dunno if its true, or not - never looked it up - but I never did it.. When I started that job, I had 20/14 vision, which is Terminator good.. REALLY good vision.. Well, that went to crap slowly to the point where I can't do much of anything without reading glasses.. I had my eyes checked and don't need prescription glasses, but need reading glasses for pretty much everything else.. Also, if I put an extremely bright light on tiny text I can read it without reading glasses..
So, he might have been right - i probably ran my vision into the ground by being on computer 10 -12 hours a day.. Or, I just got older.. not sure..
Point is: I think if you CAN read printed source material, you probably should, as often as possible.. Or not.. I need to look that up..
Friendship is like peeing your pants.. Everybody can see it, but only you can feel the warmth..