It really depends on the quality of your sunglasses. When you try to protect your eyes from watching the strong sunshine directly, You need an eclipse viewer, a pair of welders' glass, black polymer filter, specialized astronomical equipment, metal coated glass or mylar filter certified for visual use. They can filter the UV radiation. By the way, optical viewfinder is forbidden. But due to the relatively poor law system to enforce the quality of the sunglasses on the market, you may get a pair of sunglasses with inability to protect your eyes even it costs you a lot of money. As we all know, our eyes protect themselves from exposing to the light more by shrinking the size of the pupils. Your tinted glasses appear to reduce the intensity of the sun to a comfortable level, so that your eyes keep dilated. Once you open again, it will hurt. Further, it would be better if you weren’t wearing them at all when you get a fake anti-UV sunglasses because it can't filter the invisible infra-red or ultra-violet radiation with dangerous amount, which will lead to retinal burns.
