There are two main types of laser damage to the human body, and some damage to the eyes and skin, but taking the necessary protective measures can completely avoid harm to people.
Laser wavelength and eye damage:
Of the laser injuries, the most serious is the eye injury in the body. Lasers with wavelengths in visible light and near-infrared light have a low absorption rate and high transmittance of the refractive medium of the eye, and the focusing ability (ie, light-gathering power) of the refractive medium is strong. When high-intensity visible or near-infrared light enters the eye, it can pass through the refractive medium of the human eye and accumulate light on the retina. At this time, the laser energy density and power density on the retina are increased to thousands or even tens of thousands of times. And lose the role of light. The coagulation and denaturation of proteins caused by overheating when the laser converges on the photoreceptor cells is irreversible damage. Once damaged, it can cause permanent blindness of the eyes. The effect of different laser wavelengths on the eyeball is different, and the consequences are also different. The damage of the far infrared laser to the eye is mainly cornea. This is because the laser of this wavelength is almost completely absorbed by the cornea, so the corneal damage is the most serious, mainly causing keratitis and conjunctivitis. Fear of light, tearing, hyperemia of eyes, decreased vision, etc. In case of far-infrared light damage, the injured eye should be covered and protected to prevent infection and symptomatic treatment. The damage to the eye caused by the ultraviolet laser is mainly the cornea and the lens. The ultraviolet laser in this band is almost completely absorbed by the lens of the eye, while COSCO mainly absorbs the cornea, which may cause the lens and cornea to be cloudy.
Laser damage to the skin:
Due to the physiological structure, the human skin has sensitive touch, pain, and temperature functions, which constitute a complete protective layer. And the skin is composed of multiple tissue layers, with different cells in each layer. When the laser shines on the skin, if the energy (power) is too large, it can cause skin damage. Of course, the lesion can be repaired by tissues. Although the function is reduced, it does not affect the overall functional structure, and the damage to the eyes is much lighter. . But it must also be highly valued. The threshold of laser damage to the skin is also very high, the output energy of various lasers varies greatly, and the range of high-power lasers currently used is very wide. The degree of laser damage to the skin is related to factors such as the dose of the laser, the wavelength of the laser, the skin tone, the moisture of the tissue, and the thickness of the cuticle of the skin. The previous three factors are the main factors.
Laser dose and degree of skin damage:
After a lot of practice, the greater the laser power density (or energy density) used when irradiating the skin, the greater the damage to the skin, and there is a positive correlation between the two. After the skin absorbs laser energy that exceeds the safety threshold, the skin on the exposed area will appear thermally induced erythema, blisters, coagulation and thermally induced carbonization, boiling, combustion and thermally induced vaporization with increasing dose. Therefore, the mechanism of laser damage to the skin is mainly caused by the thermal effect of the laser. After the skin absorbs laser energy, the local skin temperature rises within a short period of time, and the degree of temperature rise is different, causing different damage. In particular, infrared lasers are prominent, such as CO2 lasers (vapor lasers). The skin has a high absorption rate of 10.6 μm wavelength infrared lasers and low transmittance. The skin absorbs CO2 lasers strongly, causing the local temperature of the skin to rise rapidly. High, very easy to cause damage. The severity of laser damage to the skin is determined by the skin's laser absorption rate, which is determined by the laser's wavelength. The higher the skin's absorption rate of a certain wavelength of laser, the more serious the damage will be. For example, when the skin's absorption rate of ultraviolet laser and infrared laser is very high, these two types of lasers are the main band lasers that damage the skin.
The main effect of infrared laser on the skin is thermal burns. This kind of laser irradiates the skin, and the power is relatively small, causing the capillaries to dilate, and the skin is red and fever. As the laser power density increases, the degree of thermal damage also increases. On the contrary, the effect of ultraviolet laser on the skin is mainly light. When irradiated with ultraviolet laser light on the skin, it can cause skin erythema and aging, and can cause severe carcinogenesis when overdose. Ultraviolet light waves that are most harmful to the skin are between 270 and 290 nm, and wavelengths larger or smaller than 270 to 290 nm are relatively less harmful.
The YAG infrared laser with a wavelength of 1.064um is less harmful to the skin.