Hello, I have a question about blue light coatings. A patient came in wanting a blue light filter for their eyeglasses. We sell mostly essilor lenses. The first thing I thought of was Crizal Prevencia . The patient had a blue light test kit. (a small pen light and a test card). He had a pair of $16.00 clear plano computer glasses that were designed to block 100% blue light. We test the glasses with his checker and the test card did not turn dark. We tested a Prevencia sample and the card turned dark. I called my essior rep and he said prevencia blocked 20% blue rays and Essilor doesn't not make a 100% blue blocker. I tested a yellow sunglass lens with his test light and the card turned dark.
What do you think of these test kits? What kind of light are they emitting? Specs?
Does anyone make a 100% blue blocking coating that we can use on lined bifocal? Would 100% blue blocking be beneficial.

Thanks in advance!