Leica Biosystems LPC Operating Manual - Manual (Page 41)

41 Leica LP C
7.3 Biological effects of laser beams
7.3.1 Eye injuries
Because of the high degree of beam collimation, a laser serves as an almost
ideal point source of intense light. A laser beam of sufficient power can the-
oretically produce retinal intensities at magnitudes that are greater than
conventional light sources, and even larger than those produced when di-
rectly viewing the sun. Eye exposure to a direct beam can cause permanent
eye damage including blindness. Protective eyewear should always be
worn when potential exposure to direct laser beams exist.
• Due to the lens-like focusing effect of the human eye, it is 100,000 times
more susceptible to injury than the skin.
• The laser protective eyewear must always be available for the wave-
lengths of the laser used.
• However, with regard to protection from laser radiation, eye protection
equipment is the last step in the process. Engineering and administrative
controls are the first step.
• Do not wear jewelry when working with an open laser beam to prevent
the beam from being reflected in uncertain directions.
• If possible, use all protective housings, locking mechanisms and guards.
• Always use laser protective eyewear when repairing, aligning or install-
ing lasers or whenever a laser safeguard is not present.
7.3.2 Thermal injury
The most common cause of laser-induced tissue damage is thermal in na-
ture, where the tissue proteins are denatured due to the temperature rise
following absorption of laser energy.
The thermal damage process (resulting in burns) is generally associated
with lasers operating at exposure times greater than 10 microseconds and
in the wavelength region from the near ultraviolet to the far infrared. Tissue
damage may also be caused by thermally induced acoustic waves following
exposures to sub-microsecond laser exposures.
7. Appendix A – Laser Safety