What is an eye muscle cleanse?

it is the lid that cleans the eye

Muscle cleanse is a strange concept. Maybe they were talking about natural vision improvement?

Google Bates method or anything along the lines of natural eyesight improvement, which involves learning not to strain the eyes, and you will find a lot of information.

I suppose muscle cleanse could come from the idea that tense muscles make the vision unclear, relaxing them makes the vision clear.

Bates method has helped many people get rid of their glasses, including me. You don't have to pay for an expensive Ebook to learn, so avoid those. There are many good websites providing free information and some videos as well.

Did you hear somebody tell the old man that he needed a muscle clense?

Maybe it was a lens that was needed not a clenae.