Laser shooting eyes

When the laser hits the eyes, it will cause great damage to the eyes, and may even cause temporary eye damage, which will affect your vision. Therefore, it is best to avoid direct laser exposure to your eyes, otherwise you will feel great pain in your eyes and often shed tears.

Laser wavelength and eye damage: Among the injuries caused by laser, the most serious damage is to the eyes. For lasers with wavelengths in the visible and near-infrared range, the absorption rate of the eye's refractive medium is low and the transmittance is high, while the focusing ability (i.e., focusing 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 focus the light on the retina. At this time, the laser energy density and power density on the retina increase to thousands or even tens of thousands of times. A large amount of light energy is concentrated on the retina in an instant, causing the temperature of the retinal photoreceptor cell layer to rise rapidly, so that the photoreceptor cells coagulate, degenerate and die, and lose their photosensitivity. When laser light is focused on photoreceptor cells, overheating is generated, which causes protein coagulation and denaturation, which is irreversible damage. Once damaged, it will cause permanent blindness.

Different wavelengths of lasers have different effects on the eye and have different consequences. The damage of far-infrared laser to the eyes is mainly to the cornea. This is because lasers of this wavelength are almost completely absorbed by the cornea, so the cornea is most seriously damaged, mainly causing keratitis and conjunctivitis. Patients feel eye pain, foreign body-like irritation, photophobia, tears, eye congestion, decreased vision, etc. When far-infrared light damage occurs, the injured eye should be covered to protect it, infection should be prevented, and symptomatic treatment should be given.

The damage caused by ultraviolet laser to the eye is mainly to the cornea and lens. Ultraviolet laser in this band is almost completely absorbed by the lens of the eye, while the mid- and far-field ones are mainly absorbed by the cornea, thus causing opacity of the lens and cornea.

2. Relationship between incident laser intensity and eye damage

The degree of laser damage to the eyes is not only related to the different wavelengths of lasers (CO2 laser 10.6μm; Nd:YAg laser 1.06μm, He-Ne laser 632.8nm), but also related to the total light energy, energy density and power density of the laser entering the eye.

Among the types of lasers, visible or near-infrared lasers do not cause acute damage to the eyes when their power density is very low. The main reason is that the power density of the laser is low. Although the retinal tissue receives the energy of laser photons and gradually becomes hotter, the heat is transferred to the surrounding tissues through molecular vibration and then to the outside of the eye. On the other hand, the heat can be transferred to the microvessels densely distributed in the choroid at the bottom of the retina, and then dissipated to the outside of the eye as the blood circulates in the microvessels. Therefore, there is no significant increase in temperature from the retina to the entire eye, or there is a slight temperature change, which is still within the range that is completely harmless to the eyes.