‘Oh my God. Oh my God.” Those are Cynthia Burke’s first words after Senator Rand Paul, an ophthalmologist, completes her eye surgery, removing the cataract in her right eye. Lying down in the operation room, Burke, a 55-year-old woman from the Ozarks town of Fredericktown, Mo., looks up. Standing above her are Paul and another ophthalmologist, Barbara Bowers, both dressed in blue scrubs. Because of her cataracts, Burke hadn’t been able to perceive much color, and couldn’t see at all in her right eye when there wasn’t natural light. But now, with the surgery just completed, Burke’s sight is already...