i do wonder how you can actually test the effectiveness of these glasses without an actual eclipse.
i have a dark spot on my retina. found out few years ago during a routine eye checkup. doctor said that it could only be caused by looking at an eclipse with naked eye. i do remember seeing an eclipse when i was a kid but with one of the glasses that were sold in the market. i can only imagine that i was stupid enough to not use it properly or it was defective.