"Adults who play a lot of action video games may be improving their eyesight, U.S. researchers said on Sunday."
"Practiced action gamers became 58 percent better at perceiving fine differences in contrast"
http://www.reuters.com/article/technologyNews/idUSTRE52S1TW20090329?feedType=RSS&feedName=technologyNews
I think what they are saying is probably true except I know my distance vision is wrecked after a long game session so kind of balances out.