It has been thought that violent computer games offer nothing good to those who play them, except perhaps to help young males let off steam vicariously. But now a brain scientist at Tel Aviv University's Goldschlager Eye Institute has found that playing them improves their real-world eyesight. "As a father and brain scientist, I was quite concerned when my kids were playing video games," says Dr. Uri Polat, who partnered with the University of Rochester to carry out the new study. "What we see now is that teens who play violent video games are also training their brains to see better." Results of the study were recently reported in Nature Neuroscience. Polat and his collaborators compared the effects of playing violent action games like Unreal Tournament 2004 and Call of Duty 2 to other videogames that don't require high levels of visual-motor coordination, like "The Sims." Administering a standardized visual test to 22 game-playing teenagers, Dr. Polat assessed the teens' contrast sensitivity function (CSF) - the primary factor used by ophthalmologists to measure the quality of a person's eyesight. Usually, improvements in CSF are found only when eye doctors prescribe glasses or contact lenses, or the person undergoes surgery. Surprisingly, the researchers discovered that playing violent video games enhanced the ability of young game players to discriminate between subtle contrasts in color or shades of gray. In the recent study, the game-playing teens were divided into two groups. One played violent video games, and the other played The Sims 2, a role-playing game focused on a virtual community. After playing 50 hours of the assigned game over nine weeks, those who played the more violent games showed an average 43 percent improvement in their ability to discern between close shades of gray. The players assigned to The Sims showed no improvement. Studies have already shown that video games enhance motor skills and reaction time, but Polat suspected that there might be other virtues. "Many researchers had been debating if there is any effect on vision," says Polat. "I suggested that we ask scientifically. We think that the games are taking the brain's visual cortex to the limits, forcing it to adapt to the added stimuli," he concludes. Among the test subjects, researchers measured an improvement of up to 58% in contrast sensitivity. And the effects were greatest for players who were skilled at playing "first-person shooter" games. "We were able to show that action-oriented video games can improve the brain's ability to process visual information - effects which seem to last months," said Dr. Polat, who also explores the visual systems of patients at Sheba Medical Center at Tel Hashomer. While a teen's social skills may suffer from addictive game playing, the effects on the visual system appear positive, the researchers concluded.