Over the wavelength range in which many lasers operate, the skin is a strong absorber, and thereby protects the organs of the body; however, damage to the eyes is a major risk.
There are three principal types of tissue damage mechanisms for laser radiation: thermal, photochemical, and thermo-mechanical. The nature of an injury that results from laser exposure is determined by the laser wavelength, the duration of exposure, and the type of tissue that is exposed.
Ocular hazards
| | Wavelength range | Primary tissue at risk of damage |
| Ultraviolet | 180 nm – 400 nm | Cornea or lens (302 – 315 nm) |
| Visible Near Infrared | 400 nm – 1.4 µm | Retina |
| Medium & Far Infrared | 1.4 µm – 1 mm | Cornea or lens (1.4 – 3.0 µm) |
Retinal eye damage from laser radiation can occur at very low power levels due to the focusing effect of the cornea and lens of the eye, and the coherence of laser radiation.
For very short exposures (< 10-6 s), damage arises primarily from thermo-acoustic transients. Simple heating effects predominate in the range 100 ms – 10 s. For exposures longer than 100 s, photochemical effects can predominate if the wavelength is less than 600 nm.
Skin hazards
The biological effects of skin exposure to laser radiation are simpler to assess than those of eye exposure. The primary injury is surface burning, which can occur in just a fraction of a second. Photochemical burns can result from skin exposure to UV laser beams and could result in longer term issues, such as a higher risk of skin cancer. Unlike retinal eye burns, skin burns can usually be treated. They are sterile and generally heal quickly.
Laser damage mechanisms for skin tissue are similar to those for the eye, in terms of the effect of wavelength and duration of exposure.
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