The source is some old “Top 10 Oldies Myths” article from About.com. Never cite wikipedia. Cite the source.

In all my years, I’ve never heard a single person say they ever thought he was blind. I have a really hard time believing this was ever commonly believed.

I’m not disputing that you might have believed it and that some other people might have believed it, too. It’s just, I doubt it was a common thing.