We all know how Beethoven went deaf later in his life, yet kept composing. Lesser known is the story of Johann Sebastian Bach's sight, which was always weak but he eventually went blind before he died. Bach underwent cataract surgery twice.
In the 18th century, those who suffered from cataracts, or cloudy lenses, had only one surgical treatment available. It involved "couching," or separating the lens from the front of the eye, which could restore some vision. Replacement was not possible at the time. Bach, at age 65, turned to famous eye surgeon John Taylor, who called himself an "ophthalmiater." Taylor was famous in some places for his skill at eye surgery and in others for the disastrous results of his eye surgery. A look into his techniques would make any modern patient shudder. Taylor performed cataract couching on Bach twice. We don't know if those involved a surgery on each eye, or an attempt at repair after a failure, but we know they led to Bach's blindness and death within a few months. Read about Taylor and what he did to Bach (and later composer George Frideric Handel) at Amusing Planet.