???????It is harmful for the laser to shine directly on the eyes. Laser is the abbreviation of light amplified by radiation. Its English word laser (laser) is the abbreviation of light amplification by stimulated emission of radiation. The laser is to achieve light amplification by stimulated emission of radiation. The difference between it and ordinary light is that ordinary light (such as the sun and electric lights) is emitted in all directions, and its amplitude, frequency, and phase are disordered, and the laser is along a Directional propagation, its amplitude, frequency and phase are neat and orderly, so it has the characteristics of good monochromaticity, strong directivity and high brightness. Because the brightness of the laser is very high, the energy produced by the low-power laser is similar to that of sunlight. The result of frequent exposure to laser light is the same as the glare of sunlight.
The mechanism of laser damage to human eyes is very complicated. There are three main damage effects: 1. Thermal effect: the laser light is converted into heat energy after being absorbed by the tissue, and the local temperature rises, causing protein damage and damage to the cells; 2. Shock wave effect: the retina is short Received strong light irradiation for a period of time, due to the impact of photons and the rapid thermal expansion of the irradiated tissue, resulting in the generation of shock waves and spreading to the surrounding tissues causing injuries; 3. Photochemical effect: laser irradiation of eye tissue causes the vibration of atoms and molecules in the tissue Electromagnetic effects and ionization cause tissue damage. Laser damage to the eyes is often caused by several effects at the same time.
The human eye is the most susceptible part of human organs due to laser damage. This is because the retina and other tissues can effectively absorb lasers of various wavelengths, and the eyeball itself has a good focusing system, which allows the laser light to enter the pupil and reach the retina. The energy density increases, so the damage threshold of laser to eye tissue is much lower than other organs, and the macular area is more sensitive. Moreover, the biological effects of laser can have a cumulative effect. Single exposure does not cause damage, but multiple exposures may cause damage. Victims who are repeatedly exposed to laser light often do not have obvious complaints, and only feel that their eyesight gradually declines.
The location of laser damage to eye tissue is related to the wavelength of the laser. Ultraviolet light below 300nm cannot pass through the eye refractive medium, and almost all of it is absorbed by the cornea, which can cause electro-optic ophthalmia; 300nm ～ 400nm ultraviolet light is mainly absorbed by the crystal, which can cause radiant cataract; 400nm ～ 800nm ??visible light and 800nm ??~ Near-infrared light of 900nm can reach the retina through the refractive medium, and is absorbed by the pigment cells, causing retinal burns and even bleeding; 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, lens, etc.
Laser damage to eye tissue is also related to some other factors. For example: the greater the energy of the laser, the greater the damage to the eye; the smaller the angle at which the laser illuminates the eye, the greater the damage, because the smaller the angle of incidence, the smaller the spot on the retina, the more concentrated the energy density; if the eye is square Laser beam, the laser is focused on the fovea of ??the retina, which has a greater impact on vision; at night, it is more likely to cause retinal damage than during the day, because the pupil dilates at night, and the laser energy received by the retina is more when the laser energy of the same energy density is radiated. .