(1) The laser beam is of great value in surgery because the beam can be
focused to a fine point by a single optical lens. This results in sufficient power density to
vaporize tissue giving a sharp, clean incision. There is little or no bleeding since blood
vessels are cauterized by the heat of the laser beam, and once the vaporized material is
suctioned off, the entire site is free of debris. The depth of the cut is adjusted by
reducing the beam focus and increasing the scan speed. When laser surgery is being
performed, wet towels must be draped over exposed metal, and nonexplosive
anesthetic gases must be used.
(2) Ophthalmologists have needed an intense beam of light which could be
focused into small areas at the back of the eyeball to weld a detached and torn retina.
Today a very carefully controlled laser beam can fill that need. The retina, which
captures images of the things we see, sometimes comes loose from the back of the
eye. This causes poor vision. A low-power laser beam the size of a pinpoint can pass
through the clear parts of the eye. When the beam hits the retina, the photons pile up
welding the damaged area back in place.
Figure 2-17. Eye surgery with laser beam.