The Centers for Disease Control estimates that 3.8 million people get concussions from recreational sports every year. What's worse is that half of those concussions may be going undiagnosed. A team at the University of Washington wanted to do something about this, so they developed PupilScreen. The tech enables anyone with an iPhone to detect concussions and brain injuries. Lynn McGrath Jr., one of the Neurological Surgery Residents on the team, joins Cheddar to explain the development and why accessible concussion diagnosis tools are needed.