Woodcut of a man wearing an eyeshade as treatment for yellow cataract. Cataracts are an opacity of the lens of the eye or the membrane that covers it, causing impairment of vision or blindness. Appeared in Ophthalmodouleia by Georg Bartisch (1535-1607) a German physician. He began his medical career, at the age of 13, as an apprentice to a barber surgeon. He was considered a skilled practitioner of ocular medicine and surgery. His Renaissance manuscript on ophthalmic disorders and eye surgery, Ophthalmodouleia Das ist Augendienst (1583), discussed ocular diseases, surgical techniques, instruments, including woodcuts depicting diseases of the eye. Despite his skill as a surgeon, he was a superstitious individual, as he believed that magic, astrology and witchcraft played a significant part in medicine.