[Laser in dermatology: biological effects; indications (author's transl)]

The various laser-systems can be classified according to: 1) the wavelength or range of wavelengths of the beam and 2) the method of delivery of the laser output: continuous or pulsed. -- Principal continuous-wave lasers are: -- the argon-ion laser, which produces multiple transitions ranging from 448 to 544 nm, -- the neodymium yttrium aluminium garnet (Y. A. G.) operating in the near infrared at a wavelength of 1,060 nm, -- and the carbon-dioxide laser with its output occurring in the far infrared, at 10,600 nm. Continuous-wave lasers induce essentially thermal effects which are used to coagulate or volatilize various superficial skin lesions. But when high power density is required, the relative benefit of lasers as compared with other conventional thermal devices (such as high-frequency electrocoagulator) is not obvious. On the other hand, the argon laser is capable of selectivity damaging pigmented cutaneous lesions with satisfactory healing of the laser wound and sparing of the overlying skin. This selective absorption is useful in the treatment of some vascular lesions such as port-wine stain or melanotic lesions or tattoos, and gives a good results. The specific color absorption is not so pronounced with the Nd-YAG laser and is absent with the carbon dioxide laser, chiefly used as an "optical scalpel". Photochemical effects produced by other continuous-wave lasers such as U.V. lasers, seem to be of interest in photobiology research and in destruction of tumors after the addition of a colorant. -- Pulsed laser systems produce not only thermal but also "non-linear" reactions, which are not well-known. The classical ruby laser is still appropriate in the treatment of some skin lesions.