I'm short-sighted. And I have astigmatism.
Astigmatism is a type of refractive error in which the eye does not focus light evenly on the retina.
WHile in the process of sorting out my closet, I found an old pair of glasses that I have not worn for nearly ten years. Not at all in my strength, of course. Why did I keep them? I have no idea honestly. In case I ran out of contact lenses and lost my current glasses? That seems, unlikely but it is the only thing I can think of.
More likely, I think I didn't know what to do with them and I was reluctant to discard them. So I kept a pair of glasses that no longer fulfilled their, because while obsolete, I felt that it was a waste to get rid of them.
When I found them, I decided to get rid of them. Finally. But how? The Internet being a close friend as she is I decided to ask. And as the Internet is funny like that, in a nice way, she answered me.
Apparently, some opticians take them back and send them to underprivileged countries. But you will have to see on a case to case basis. Some of them work like the appliance sellers: "I'll take them back if you bought them here" or "I will take them if you buy a new pair."
There are associations that recycle glasses. Just send them glasses, frames, sunglasses, cases, hearing protection and hearing aides. Volunteers receive, sort and measure the characteristics of item and pass them on to hospitals and clinics in developing countries around the world.
Controversy about donations do exist. This article on Bloomberg highlights some of the points. So you will have to make up your own mind about the process and see if it fits your expectations.