The first hazard of blue light is damage to the tissue structure of the eye. Harmful blue light has extremely high energy and can penetrate the lens directly to the retina, causing atrophy or even death of retinal pigment epithelial cells. The death of photosensitive cells will lead to vision loss or even complete loss of vision, and this damage is irreversible. Blue light also causes macular degeneration, where the lens in the human eye will absorb some of the blue light and gradually cloud to form cataracts. Most blue light penetrates the lens, especially in children, where the lens is clearer and cannot effectively resist blue light, thus making it more likely to cause macular degeneration and cataracts. The second hazard of blue light is that it is easy to cause visual fatigue. Because of the short wavelength of blue light, the focus does not fall on the center of the retina, but a little bit more in front of the retina, trying to see clearly, the eye will be in a state of tension for a long time, causing visual fatigue. Long-term visual fatigue can lead to myopia deepening and diplopia. The inability to concentrate when reading affects people’s learning and work efficiency. The third harm of blue light is to affect sleep. Blue light will inhibit the secretion of melatonin, which is an important hormone that affects sleep, and is known to promote sleep and regulate jet lag. Therefore, prolonged stimulation by blue light may cause poor sleep quality as well as difficulty in falling asleep.