In the sun, people usually adjust the pupil size to adjust the luminous flux. When the light intensity exceeds the eye's ability to adjust, it will cause damage to the human eye. Sunglasses can block the sun to reduce eye strain or damage caused by strong light. Wearing inferior glasses, the eyes look like things in the darkroom, the pupils will become larger, and the residual ultraviolet rays will be injected into the eyes in large quantities, causing the eyes to be hurt.
In addition, the surface of the lens is not smooth, and the external object will be deformed and distorted, causing the eye to sore, followed by visual fatigue such as nausea, loss of appetite, forgetfulness, and insomnia. In addition, when it is not necessary to wear sunglasses when it is not necessary to wear sunglasses on cloudy days and indoors, it will increase the burden of eye adjustment, causing tension and fatigue of the eye muscles, causing vision loss, and dizziness, long-term vision, etc.
Regular sunglasses belong to the series of plain glasses. According to national standards, the diopter tolerance of plain glasses is ±0.08D, and there is no optical defect that affects vision. Once the diopter exceeds the standard, it will make the eyes feel tired, hurt vision, and even be "cultured" into myopia or hyperopia patients. There is a simple way to identify the quality of the lens: place the sunglasses in front of your eyes and shake them to see if the object moves with the lens. If you move together, it means that the lens has diopter, which will be bad for the eyes. And the surface of the lens should be smooth, free of ripples, flawless, no bubbles, no wear marks.