Ballroom, colorful lights flying around, colorful, crowd bustling, and the beat of the music is dancing, in the giddy, do you feel that the flying lights are particularly blinding, and even make people feel that they can not see anything in front of their eyes, only a sense of flash; streets and alleys, children with laser pointer shine around, but also can change the tip of the pen to shine a variety of shapes, such as stars, arrows or small animals, sometimes Sometimes naughty children will use the laser pointer directly into the eyes of other children, shining the eyes to see things straight blurry. This often happens in daily life may not attract attention, but unknowingly some people’s eyesight will slowly decline, which is mentioned earlier “lights” have anything to do with it? In fact, these beautiful lights are small laser emitters emitted by the laser, direct exposure to the eyes is harmful. Laser is the abbreviation of light amplification by stimulated emission of radiation, its English word laser (laser) is light amplification by stimulated emission of radiation the first letter of the abbreviation. Laser is light amplification by stimulated emission of radiation, the difference between it and ordinary light is that: ordinary light (such as the sun, electric lights) is emitted in all directions, its amplitude, frequency, phase are disorderly, while the laser is propagated along a direction, its amplitude, frequency, phase neat and orderly, so it has good monochromatic, directional, high brightness characteristics. Due to the high brightness of the laser, the energy produced by a low-power laser is similar to that of sunlight, and the result of frequent exposure to laser light is the same as frequent exposure to blinding sunlight. The mechanism of laser damage to the human eye is complex, there are three main destructive effects: 1, thermal effect: the laser is absorbed by the tissue into heat, the local temperature increases, so that protein destruction, cell damage; 2, shock wave effect: the retina in a short period of time to receive intense light exposure, due to photon impact and rapid thermal expansion of the irradiated tissue, resulting in the generation of shock waves, and spread to the surrounding tissue and cause injury; 3. Photochemical effects: laser irradiation of eye tissue causes vibrations of atoms and molecules in the tissue, resulting in electromagnetic effects and ionization to cause tissue damage. Laser damage to the eye, often several effects work simultaneously. The human eye is the most vulnerable part of the human organ to laser damage, which is due to the fact that the retina and other tissues can effectively absorb multiple wavelengths of laser light, and the eye itself has a good light gathering system, so that the laser enters the pupil and reaches the retina with an increased density of light energy, so the threshold of laser damage to eye tissue is much lower than other organs, and the macula is more sensitive. Moreover, the biological effect of laser can have a cumulative effect, and a single exposure does not cause damage, but multiple exposures may cause damage. Victims of repeated laser exposure to the eye often have no obvious complaints, but only feel a gradual loss of vision. The wavelength of the laser is related to the site of damage to the eye tissue. 300nm or less UV light cannot penetrate the refractive medium of the eye, and almost all of it is absorbed by the cornea, which can cause electro-optic uveitis; 300nm-400nm UV light is mainly absorbed by the crystal, which can cause radiation cataract; 400nm-800nm visible light and 800nm-900nm near-infrared light can The visible light from 400nm to 800nm and near-infrared light from 800nm to 900nm can reach the retina through the refractive medium and be absorbed by the pigment cells, causing retinal burns and even hemorrhage; the infrared light above 950nm can be absorbed by the refractive medium of the eye and damage the superficial tissues of the eye in the form of thermal radiation: cornea, crystal, etc. Laser damage to eye tissues is also related to a number of other factors. For example, the higher the energy of the laser, the greater the damage to the eye; the smaller the angle of laser irradiation, the greater the damage, because the smaller the angle of incidence, the smaller the spot on the retina and the more concentrated the energy density; if the eye looks directly at the laser beam, the laser is focused in the central recess of the retina, which has a greater impact on vision; at night is more likely to cause retinal damage than during the day, because the pupil is dilated at night, and when subjected to the same energy density of laser radiation, the retina is more likely to be damaged. The retina receives more laser energy when exposed to the same energy density of laser radiation. According to the national standard, the laser power of 0.1 seconds or more should not exceed 10-4 watts, which is the safety threshold of laser. Our daily exposure to laser light generally does not exceed this standard, but often exposed to laser and not pay attention to protection, but also the usual chronic damage. Once an eye injury occurs, it will be too late to remedy it, because the death of retinal photoreceptor cells and pigment cells caused by laser is irreversible. Therefore, in our daily life we must pay attention to protect our eyes, try to avoid laser exposure, and never look directly at the laser because of curiosity or fun.