One of my friends is severely visually impaired (blind in one eye, very limited vision in the other) and yet is the most talented guitar player I know personally. Excellent at improv chords (played Eye of the Tiger on-the-fly for an audience one night after strumming the melody once), probably helps that he can't read sheet music. He specializes in the bouzouki and plays gigs at traditional Greek Orthodox weddings.
If anyone cares:
sample bouzouki (friend playing guitar .. gets interesting around 2:08 .. apologies for my crappy recording)
sample recording (performed and compiled by him)