The laws of thermodynamics do not limit the power of lasers. A laser beam with low divergence entering the eye can be focused down to an area 10 to 20 microns in diameter. Just as a magnifying glass can be used to focus the sun and burn wood, the lens in the human eye focuses the laser beam into a tiny spot than can burn the retina.
The eye is the organ most sensitive to light. The major danger of laser light is hazards from beams entering the eye. A surface that would be a diffuse reflector for a visible laser may be a specular reflector for an infrared laser beam. Whether a surface is a diffuse reflector or a specular reflector will depend upon the wavelength of the beam. Diffuse reflections from Class 4 lasers are capable of initiating fires.
#RETINA BURN FULL#
These reflections do not carry the full power or energy of the primary beam, but may still be harmful, particularly for high powered lasers. Mirror-like surfaces that are not completely flat, such as jewelry or metal tools, may cause diffuse reflections of the beam.
#RETINA BURN SKIN#
Curved mirror-like surfaces will widen the beam such that while the exposed eye or skin does not absorb the full impact of the beam, there is a larger area for possible exposure.Ī diffuse surface is a surface that will reflect the laser beam in many directions. Specular reflections from mirror surfaces can be nearly as harmful as exposure to the direct beam, particularly if the surface is flat. The eye or skin is exposed to the full irradiance or radiant exposure possible. Intrabeam exposure means that the eye or skin is exposed directly to all or part of the laser beam. Particularly for high powered lasers, exposure to beam reflections may be just as damaging as exposure to the primary beam. PhotobiologicalĮxposure to the laser beam is not limited to direct beam exposure. Table 2 summarizes the probable biological effects of exposure of eyes and skin to different wavelengths. Photochemical effects depend greatly on wavelength. A change in cell chemistry may result in damage or change to tissue.
This happens when the laser beam causes localized vaporization of tissue, causing the shockwave analogous to ripples in water from throwing a rock into a pond.īeam exposure may also cause photochemical effects when photons interact with tissue cells.
The severity of the damage is dependent upon several factors, including exposure duration, wavelength of the beam, energy of the beam, and the area and type of tissue exposed to the beam.Īcoustical effects result from a mechanical shockwave, propogated through tissue, ultimately damaging the tissue. Thermal effects are caused by a rise in temperature following absorption of laser energy. The biological damage caused by lasers is produced through thermal, acoustical and photochemical processes. Effects can range from mild skin burns to irreversible injury to the skin and eye. Improperly used laser devices are potentially dangerous. The hazards of lasers may be separated into two general categories – beam related hazards to eyes and skin and non-beam hazards, such as electrical and chemical hazards.
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