This article introduces the classification of ophthalmic lasers, the characteristics of different wavelengths of lasers, and the absorption wavelengths of different tissues.

Ophthalmic lasers are divided into three categories: gas, liquid and solid lasers. Among them, gas lasers are further divided into three types: molecular (CO2 molecules), atomic (helium-neon atoms) and ion (argon ions and krypton ions) lasers. Liquid lasers have dye lasers. Solid-state lasers include ruby laser, Nd: YAG laser, and semiconductor laser. There are two ways of application: intraocular and extraocular. Intraocular lasers are used inside the eye during vitreous surgery. There are two ways to use the extraocular laser, one is through the pupil and the other is through the sclera.

Blue-green laser: The shallowest penetration depth, acts on the inner and outer layers of the retina, and is mainly absorbed by RPE, such as argon laser.

Green laser: tissue penetration is stronger than blue light, absorbed by hemoglobin and RPE, 57% absorbed by RPE, and 47% absorbed by choroid.

Yellow laser: The retinal nerve fiber layer has little diffusion and strong penetration, and the yellow laser is absorbed by the RPE layer and the choroidal inner layer each accounting for 50%.

Red and infrared lasers: the strongest penetrating power, mainly acting on the middle and outer layers of the choroid. The absorption of red laser light by the choroid increases gradually with increasing wavelength.

1. The penetration of the laser wavelength from 400 to 950 nm in the eye can reach 95%. The absorption rate of RPE and choroid can reach 70% at the wavelength of 450~630nm. As the wavelength increases, the absorption rate drops rapidly, so the argon laser (blue-green) laser and the 532 laser are the most commonly used laser spectra in the eye.
2. Hemoglobin absorption characteristics of light: At the wavelength of 400~600nm (blue to yellow part), hemoglobin has a high absorption rate, and the wavelength above 600nm (red and near-infrared) is very absorbed by hemoglobin, so 600nm (red) can be used when there is subretinal hemorrhage. above laser.
3. Absorption characteristics of lutein: Lutein is the photoreceptor pigment of cone cells. It has a high absorption peak for wavelengths below 480nm, which is easy to cause damage to lutein. In order to avoid damage, it is safer to use wavelengths above green for cone cells. Among them, 810 laser minimal damage to it.