When Kenneth Watson was 16, he thought nothing of the gnat that flew into his eye: "I don't think you can afford to be afraid of bugs in the Bible Belt," he said. But two weeks later when the Hardy, Ark., teen was getting ready for school, he knew something was terribly wrong when he couldn't see. When he told his mother, she thought he was faking. "I had slept late and my mom thought I was skipping school," he said. "Sometimes I would come up with crazy stories, and she told me to get up and get ready." As...