This is goofy. The melanin in the skin is produced by the skin; it has nothing to do with the eyes or what the eyes see. (Same thing with vitamin D.) The eyes do not respond to UV; the lens filters it out. Excessive UV will hasten the aging of the lens toward the formation of a cataract. UV blocking is a design requirement for artificial lenses. It is bad for the retina. If the sunglasses cut light intensity by 50%, that will not harm you. The natural variation in eye sensitivity is much greater than that. Polarized lenses will do that, and also block light that is horizontally polarized, such as reflections off water, which is a primary source of glare. You get all the blue light you need from skyshine (which makes fear of computer screen blue light kind of silly).
I'm speaking from a career involving making intraocular lenses and having read all of a thick university textbook on ophthalmology. If you think this is a good idea, go up on the ski slopes sometime without eye protection and go blind. There is the famous scene in "The Four Feathers" (1939) where Ralph Richardson's character is stranded in the desert and goes blind from the overwhelming sunlight. The moment is captured in the Miklos Rozsa score by the sound of a hammer hitting an anvil. (A good film and a good story, as a meditation on courage.)
This is goofy. The melanin in the skin is produced by the skin; it has nothing to do with the eyes or what the eyes see. (Same thing with vitamin D.) The eyes do not respond to UV; the lens filters it out. Excessive UV will hasten the aging of the lens toward the formation of a cataract. UV blocking is a design requirement for artificial lenses. It is bad for the retina. If the sunglasses cut light intensity by 50%, that will not harm you. The natural variation in eye sensitivity is much greater than that. Polarized lenses will do that, and also block light that is horizontally polarized, such as reflections off water, which is a primary source of glare. You get all the blue light you need from skyshine (which makes fear of computer screen blue light kind of silly).
I'm speaking from a career involving making intraocular lenses and having read all of a thick university textbook on ophthalmology. If you think this is a good idea, go up on the ski slopes sometime without eye protection and go blind. There is the famous scene in "The Four Feathers" (1939) where Ralph Richardson's character is stranded in the desert and goes blind from the overwhelming sunlight. The moment is captured in the Miklos Rozsa score by the sound of a hammer hitting an anvil. (A good film and a good story, as a meditation on courage.)