The so-called sunshade, as the name implies, is used for shading. People usually adjust the luminous flux by adjusting the size of their pupils in the sun. When the light intensity exceeds the adjusting ability of the human eye, it will cause damage to the human eye. Therefore, in outdoor activities, especially in summer, many people use sunshades to block out the sun, to reduce the fatigue caused by eye adjustment or the injury caused by strong light stimulation.

Light-color sunglasses are not as effective as sun visors in blocking sunlight, but they are rich in color, suitable for use with various kinds of clothing, and have a strong decorative effect. Light color sunglasses are favored by young people because of their rich colors and diverse styles, and fashionable women are even more fond of them. Sunglasses for special purposes have a strong function of shielding the sun. They are often used in the fields where the sun is strong, such as beaches, skiing, mountain climbing, golf, and so on. Their UV resistance and other indicators have high requirements.

Different people choose sunglasses according to their different preferences and uses, but the most fundamental thing is to start from the basic principle of ensuring the safety of the wearer and the protection of vision. It should be the basic function of sunglasses to reduce strong light stimulation, keep the object clear without distortion, prevent the ultraviolet, recognize color without distortion, and accurately identify traffic signals. If the above functions are defective, it may lose the function of sunglasses at the light level, and it may cause self-conscious maladaptation symptoms such as dizziness and eye soreness at the heavy level. Sometimes it may also produce symptoms such as slow reaction, color discrimination illusion, walking, and visual inequality, and cause traffic accidents. Therefore, when choosing sunglasses, we should not only pay attention to the style but ignore its internal quality.