Fast-paced shoot 'em up video games such as Unreal Tournament can improve players' vision, scientists have reported.

Researchers at the University of Rochester have shown that people who play action video games for a few hours a day over the course of a month improved their vision about a fifth when it came to identifying letters presented "in clutter".

"In essence, playing video game improves your bottom line on a standard eye chart," the scientists reported.

Daphne Bavelier, professor of brain and cognitive sciences at Rochester, said: "Action video gameplay changes the way our brains process visual information.

"After just 30 hours, players showed a substantial increase in the spatial resolution of their vision, meaning they could see figures like those on an eye chart more clearly even when other symbols crowded in."

Professor Bavelier and graduate student Shawn Green tested college students who had played few, if any, video games in the past year.

At the outset, the students were given a 'crowding' test, which measured how well they could discern the orientation of a 'T' within a crowd of other distracting symbols.

Students were then divided into two groups. The experimental group played Unreal Tournament for roughly an hour a day. The control group played Tetris, a game equally demanding in terms of motor control, but visually less complex.

After about a month of near-daily gaming, the Tetris players showed no improvement in sight, but the Unreal Tournament players could tell which way the 'T' was pointing much more easily than they had a month earlier.

"When people play action games, they are changing the brain's pathway responsible for visual processing," explained Professor Bavelier.

"These games push the human visual system to the limits and the brain adapts to it. This learning carries over into other activities and possibly everyday life."