When exposed to ultraviolet rays and short-wave visible light in the sun, the color of photochromic lenses darkens and the light transmittance decreases; indoors or in a dark place, the light transmittance of the lenses increases and the color fades and the eyes recover. The lens can adjust the light transmittance by changing color, so that the human eye can adapt to the changes in ambient light, reduce visual fatigue, and protect the eyes.
