BOSTON (AP) _ To doctors' amazement, experimental new medicines are rescuing people from the brink of blindness so they can read and drive and sometimes even regain perfect vision. These lucky few are the first beneficiaries of an entirely new category of drugs that many hope will revolutionize the care of common eye diseases. Several competing medicines are in development, all based on similar principles. They are designed to stop the two top causes of adult blindness _ the ``wet'' form of macular degeneration, which affects the elderly, and diabetic retinopathy, the biggest source of blindness in working-age people. Vision...