I enjoyed gba sp ds lite psp. My eyesight is worse I do not enjoy gaming on small screens like I used to I traded in my ds lite purchased component cable to play psp purchased gamecube gb player to play my gb gbc gba on big screen tv.
I did portables contributed to worse eyesight many fun games on portables I do not want to give it up but worse health novelty of playing console quality games on small screens is gone I will play my portable games on the big screen.
When my friend first got a psp I couldn't play it because it seemed to mess with me to stare at the screen (this was about 4 years ago when I was 24) but I bought one anyway and have had no problems. Maybe you just need glasses? Or English lessons?
Staying awake on meth for a week at a stretch playing handheld games is bound to cause a bit of eyestrain. Soon your heart will explode and it will no longer be an issue.