Test subjects were given an eye test similar to the one used at regular eye clinics and then divided into two groups -- one played shoot-em-up action games for an hour a day while the control group played a less visually complex game.

Their vision was tested after the study, with those who played the action game scoring better in the eye test.
aus: http://news.yahoo.com/s/nm/20070207/...ames_vision_dc