Sunglasses, also called sunshades, are used for sunshades. In the sun, people usually need to adjust the pupil size to adjust the luminous flux. When the light intensity exceeds the ability of the human eye to adjust, it will cause harm to the human eye.

Therefore, outdoor activities, especially in summer, need to use sunshades to block sunlight to reduce fatigue caused by eye adjustment or damage caused by strong light stimulation.