Relationship between incident laser intensity

by:LASERRPAIR     2020-06-05
?????The degree of laser damage to the eyes is not only related to lasers of different wavelengths (CO2 laser 10.6 μm; Nd: Yag laser 1.06 μm, He-Ne laser 632.8 nm), but also related to the total light energy, energy density and power density of the laser entering the eye United. Among the types of lasers, when the visible or near-infrared laser power density is very low, it does not cause acute eye damage. The main reason is that due to the low power density of the laser, the retinal tissue gradually heats up after receiving the laser photon energy, but on the one hand, the heat is transferred to the surrounding tissue through molecular vibrations, and then to the outside of the eye; on the other hand, the heat can be transferred Give the microvessels densely packed in the choroid of the bottom of the omentum, and then circulate outside the eye as the blood circulates in the microvessels. Therefore, the temperature of the retina to the whole eye does not increase significantly, or slightly changes in temperature, and it is still in a range that is completely harmless to the eye. The damage to the retina depends on the power and time. For example, when the power density of the visible or near-infrared continuous laser is increasing, the heat accumulation speed on the retina is greater than the heat dissipation speed, or the power density is not very high, but the retina absorption time is too long. The temperature of the part where the retina receives photon flow must rise, that is, the longer the irradiation time, the greater the temperature rise, and the greater the temperature rise. If it exceeds the normal eye temperature by more than 10 ° C, it will cause retinal damage. 1. Pupil size and degree of damage pupil size has a certain proportional relationship with the degree of injury. A reduced pupil can reduce the amount of laser light entering the fundus. The larger the pupil, the greater the amount of laser light entering the eye, and the more serious the fundus damage, the more irreversible. Therefore, pupil reduction has certain significance for protecting the fundus retina and preventing laser beam damage. 2. The change of the pupil is different from the environment. In a dark room, the pupils are spread apart. In debugging in such an environment, those who use lasers must carefully protect their eyes. Therefore, when the pupil of the eye is outside the maximum state, although the amount of light entering is small, it is also the easiest to damage the retina of the eye. In addition to reducing the amount of light entering the pupil, the amount of laser light outside the pupil can be absorbed by the iris, and the heat can be diffused and transferred by the microvessels of the iris. The eyes of the average person, when adapting to a dark environment, have a pupil diameter of 7 to 8 mm, which can be reduced to only 1.5 mm under visible strong light, and usually have a pupil diameter of about 2 to 3 mm during the day. Therefore, the light transmission area between the largest pupil and the smallest pupil differs by more than 20 times.
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