When did Edgar degas lose his eyesight?

Well first off, he was never blind. But he did have bad eyesight during his late 30's and became worse as life went on. He was a guard and the harsh cold and bright sun damaged his sight. Later on he found out he couldn't see with his right eye! He got a little less work to do as a guard but, his eye sight was still getting poorer. Soon he had to ask his models to tell him which color was which and couldn't read. I guess you could say he was blind but blind means can't see at all. He could see very little.