Excellent question Acorn4. I don't know why that never occurred to me. It seems so obvious. I should have mentioned where I got the information my first post about the blues singers and how they lost their sight. I simply googled biographies of each of the blind blues singers that I could think of.
People like Ray Charles and Jose Feliciano wear (wore) glasses, but it doesn't seem so odd for a blind person to wear shades. Perhaps Blind Lemon was blind in the legal definition of the word, with some vision.