Sunglasses, also known as Shade mirror, for shading purposes.
People in the sun usually to adjust the size of the pupil to adjust the luminous flux, when the intensity of light over the human eye to adjust the ability, it will cause harm to the human eye.
Therefore, in outdoor activities, especially in summer, need to use shading goggles to cover the sun, to reduce the eye adjustment caused by fatigue or strong light stimulation caused by injury.