Medicine: Led by the Blind

One-seventh of all the world's people suffer from trachoma. No killer, but the cause of maddening itching and burning in the eyes, it impairs vision, often leads to blindness. Now, after 50 years of frustrating efforts to find incontrovertible proof that the disease is caused by a virus, Britain's Medical Research Council reports that researchers have closed the circle of evidence. It was a blind man who helped them to see the proof they needed.

From the eye sockets of trachoma victims, investigators had no trouble getting secretions in which they found what seemed to be a large virus. The trick was...