your eyes focus on close objects by tensing tiny little muscles that distort the lens.
your eyes focus on distant objects by relaxing the same muscles.
close = tensed
distant = relaxed
do too much close work and your eyes will hurt.
as you get older the lenses in your eyes become stiffer – the lens muscles have to work harder to achieve the same focus.
as you get older the muscles that distort the lens become weaker.
how old are you monkey? – your eye muscles are working very hard for 10 hours a day, of course your eyes will hurt. just get some +1 reading glasses.
all this modern life (reading, looking at porn on tinternet, etc.) is very hard work for our eyes which evolved for a bit of tree climbing, spear chucking, and scanning the horizon for mammoths.
you’ll do enough close work in a normal day (counting your change, making a sandwich, reading a map) to stop your eyes becoming ‘weak’ and long-sighted, but asking your poor old peepers to cope with 10 hours screen-work is a bit much.
you can do it when you’re young, but it’s increasingly hard as you get older.
feel free to ignore me, but don’t ask me for sympathy when you get migraines, or your eyes ‘adjust’ to all this close work by becoming short-sighted.