The intensity of laser radiation is often such that exposure
can result in serious and permanent injury to skin and eyes.
There are also a number of non-beam hazards associated with
laser systems. These include electrical shock, exposure
to dyes and chemicals, and production of potentially hazardous
The site of injury following laser exposure depends on
the wavelength (Figure 1). Ultraviolet with wavelengths
from 0.2 to 0.215 mm and infrared with wavelengths of
1.4 mm or greater are absorbed in the cornea. Wavelengths
from 0.78 to 3 mm are also partially absorbed in the lens.
Visible light 0.4 to 0.78 mm is transmitted to the retina.
Some light with wavelengths from 0.78 to 1.4 mm will also
be transmitted to the retina.
Acute exposure of the cornea can cause corneal burns,
or photokeratitis (welder's flash). Lens opacities (cataracts)
are associated with chronic exposure of the lens. Chronic
exposure of the retina may also result in retinal injury.
All injury described above may be permanent and serious.
Exposure of the retina can be particularly hazardous,
however, as a result of the focusing effect of the lens.
A laser beam originally several mm in diameter may be
focused to a spot on the retina of 10 to 20 um diameter.
The irradiance of the original beam is intensified in
this manner by a factor of 10,000 or more!
Objects in the center of the field of vision are focused
on an area of the retina called the fovea. This area of
the retina is the most sensitive and is responsible for
most of our visual acuity. Injury of the fovea may result
in permanent blindness in the injured eye. If the peripheral
areas of the fovea are injured, the effect on vision is
less serious. In some cases the effects are not noticeable
or distracting. See Appendix F.
Skin burns are caused by radiation from high-powered
lasers in the infrared. Exposure to the skin in all wavelengths
may result in erythema, skin cancer, skin aging, dry skin
effects, and photosensitive reactions in the skin.