Sharp-eyed shooters in video games also have better vision in the real world, researchers say.

Daphne Bavelier of the University of Rochester said that very practiced action gamers -- those who play first-person shooters such as "Doom" or "Halo," for instance -- become 58 percent better at seeing fine differences in contrast.

It had been thought that the only way to improve the ability to see slight differences in shades of gray was glasses or surgery. But she said playing video games seems to train the brain about how to use the visual information.

The results are based in part on a study of 22 college students who were split into two groups. One group played "Unreal Tournament 2004" and "Call of Duty 2" for 50 hours over 9 weeks. The other played "The Sims 2."

The action-game players had 43 percent improvement in their vision. Those who played "The Sims" saw no improvement.

"When people play action games, they're changing the brain's pathway responsible for visual processing. These games push the human visual system to the limits and the brain adapts to it, and we've seen the positive effect remains even two years after the training was over," Bavelier said.