Whether it’s for sun protection, cool looks, or keeping up with trends, black sunglasses have always been popular with everyone. Black sunglasses are not only the favorite decorations of trendy men and women, but also a must-have for many people to prevent strong light in summer. Let's take a look at black sunglasses together. Black sunglasses can be said to block all visible light and do not reflect any color light. You can feel that the surrounding environment is relatively dark. In the case of strong light, you need to adjust the luminous flux by the pupil size of your eyes. Black sunglasses can reduce the stimulation of light, reduce eye fatigue caused by eye adjustment, and reduce the damage of strong light. At the same time, black sunglasses are also an excellent decoration, and because of the coldness of black, they have become a tool used by many young people to pretend to be cool. When wearing black sunglasses, there is a big difference when the eyes see the things around them and how they usually feel. This has to do with the reason why sunglasses block visible light. When looking at things, I feel that I can see more clearly when I don't wear sunglasses. In order to see more clearly, it is more laborious to use the eyes. If it is long, it is easy to cause visual fatigue. Black sunglasses make the human eye in a darker environment, and the pupil of the human eye will be dilated. If you wear black sunglasses for a long time, the pupil of the human eye will also be enlarged for a long time, and the result is that the vision will be decreased. Even if vision was particularly good before, it can have an impact. However, because the development of this kind of impact on vision is relatively slow, many people tend to ignore it. Since black sunglasses block most of the visible light out. However, because some harmful light rays are more likely to enter the eyes due to the dilation of the pupils, causing damage to the eyes. In particular, some sunglasses without UV protection and other harmful rays are still very harmful to the eyes. Therefore, in the choice of sunglasses, we must understand the function of the purchased sunglasses.