"[Backstage] she was wonderful; she was marvelous. She was easy-going and a worker. Oh my goodness! She rehearsed and rehearsed; always full-voice, never pushing the sound, but she would work till she got what was wanted. And of course had very poor eyesight. She used to pace out how many steps she would go, and there were steps and different levels on stage, as they were, in Norma. And she knew how many paces she could take before she had to take a step, because she was blind as a bat. She had terrible eyesight and, of course, couldn’t wear contact lenses at the stage. She did later."
January 1, 1970
https://en.wikiquote.org/wiki/Maria_Callas