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LASER SAFETY PAGE 1
Abstract

THE UNPROTECTED HUMAN EYE is extremely sensitive to laser radiation and can be permanently damaged from direct or
reflected beams. The site of ocular damage for any given laser depends upon its output wavelength. Laser light in the
visible and near infrared spectrum 400 - 1400 nm (the majority of lasers used in dermatology) contributes to the so-called
"retinal hazard region" and can cause damage to the retina, while wavelengths outside this region (i.e., ultraviolet and far
infrared spectrum) are absorbed by the anterior segment of the eye causing damage to the cornea and/or to the lens. The
extent of ocular damage is determined by the laser irradiance, exposure duration, and beam size. As laser retinal burns
may be painless and the damaging beam sometimes invisible, maximal care should be taken to provide protection for all
persons in the laser suite including the patient, laser operator, assistants, and observers.
Protective eyewear in the form of goggle, glasses, and shields provides the principal means to ensure against ocular
injury, and must be worn at all times during laser operation. Laser safety eyewear (LSE) is designed to reduce the amount
of incident light of specific wavelength(s) to safe levels, while transmitting sufficient light for good vision. In accordance with
the ANSI Z136.3 (1988) guidelines, each laser requires a specific type of protective eyewear, and factors that must be
considered when selecting LSE include: laser wavelength and peak irradiance, optical density (OD), visual transmittance,
field of view, effects on color vision, absence of irreversible bleaching of the filter, comfort, and impact resistance.
Ignorance of any of these factors may result in serious eye injury. As LSE often look alike in style and color, it is important
to specifically check both the Colour codingwavelength and OD imprinted on all LSE prior to laser use, especially in
multi-wavelength facilities where more than one laser may be located in the same room. Color coding of laser handpieces
and LSE may help to minimize confusion. LSE should not move between laser rooms, nor should they be carried in lab
coat pockets between use. The integrity of LSE must be inspected regularly since small cracks or loose fitting filters may
transmit laser light directly to the eye. With the enormous expansion of laser use in medicine, industry and research, every
facility must formulate and adhere to specific safety policies that appropriately address eye protection.



What are the effects of laser energy on the eye?

The site of damage depends on the wavelength of the incident or reflected laser beam:

* Laser light in the visible to near infrared spectrum (i.e., 400 - 1400 nm) can cause damage to the retina resulting in
scotoma (blind spot in the fovea). This wave band is also know as the "retinal hazard region".
* Laser light in the ultraviolet (290 - 400 nm) or far infrared (1400 - 10,600 nm) spectrum can cause damage to the cornea
and/or to the lens.


Are there any specific symptoms of laser eye injuries?

* Exposure to the invisible carbon dioxide laser beam (10,600 nm) can be detected by a burning pain at the site of
exposure on the cornea or sclera.
* Exposure to a visible laser beam can be detected by a bright color flash of the emitted wavelength and an after-image of
its complementary color (e.g., a green 532 nm laser light would produce a green flash followed by a red after-image).
* When the retina is affected, there may be difficulty in detecting blue or green colors secondary to cone damage, and
pigmentation of the retina may be detected.
* Exposure to the Q-switched Nd:YAG laser beam (1064 nm) is especially hazardous and may initially go undetected
because the beam is invisible and the retina lacks pain sensory nerves. Photoacoustic retinal damage may be associated
with an audible "pop" at the time of exposure. Visual disorientation due to retinal damage may not be apparent to the
operator until considerable thermal damage has occurred.