Parents are so worried about football brain injuries, Pop Warner has seen participation drop nearly 10% in the past couple of years. Even NFL legend Brett Favre told the "Today Show" he's worried.
"I would be real leery of him playing; in some respects I'm almost glad I don't have a son."
But a new medical device that can test for possible brain injuries could be a game-changer for parents.
"The kids would do a test before the game and then after we detect an impact with one of these impact sensors they would come to the sidelines and we'd do the same test again. If there was a change in the parameters we could make a decision on whether or not to pull the kid from the game."
Dr. Rennaker says the device is also being tested at the college level and he thinks it could someday be used in the NFL.
"The eyes are sort of a pathway to your brain function. You've got basic reflex action; pupil dilation with changes in intensity of light and you can measure how much they dilate and how fast they dilate and those may be indicators of brain injury."