lasers that can be used to treat pigment is a
result of the broad absorption spectrum of
melanin. Even so, other less pigment-specific
lasers have been used to treat pigmented lesions,
including the COZ and argon lasers. The
COZ laser exerts its effect on tissue by simple
vaporization of water-containing cells. Textural
skin changes and scarring may result from this
nonselective destruction. A very low wattage
COZ laser appears to reduce the risk of scarring
and has been used effectively to treat superficial
epidermal pigmented lesions, such as solar
lentigines.
The green and blue light (488 and 514 nm,
respectively) of the argon laser is specifically
absorbed by melanin. The problem with the
system is that it functions as a continuous
wave laser. Thus, although this laser selectively
targets the melanin chromophore, the heat
produced dissipates from the absorbing
melanosomes, causing thermal damage to
surrounding tissue with resultant hypopigmentation
and scarring.
Lasers that produce pulses of light shorter than
the thermal relaxation time of melanosomes are
now used to selectively destroy targeted
melanin. The process of removing pigmented
lesions using sufficiently shorter laser pulses is
called selective photothermolysis. The targeted
melanosome selectively absorbs the laser light and
the resultant increase in temperature induces
thermal damage of