LIGHT AND ELECTRON-MICROSCOPIC INVESTIGATION OF THE PROCESS OF HEALING OF THE NEVUS OF OTA BY Q-SWITCHED ALEXANDRITE LASER IRRADIATION

Melanocytes in the naevus of Ota were destroyed by irradiation using t he Q-switched alexandrite laser. This laser is highly selective and hi ghly absorbed by melanosomes. Other cells and tissue components of the dermis remained almost intact. Melanosomes were vaporized or fragment ed to subelectron microscopical size, or degenerated. If the irradiate d energy was sufficient, melanocytes vanished and large vacuoles sever al times the size of dermal melanocytes formed at the sites. If it was too weak, dermal melanocytes were also vaporized, but vacuoles formed within them. Nuclei were no longer discernible. Following irradiation macrophages infiltrated the irradiated areas and scavenged degenerate d melanosomes and cellular debris. Thus, discoloration of the skin was markedly reduced. Although a few melanocytes and melanophages remaine d, pigmentation cleared to a satisfactory level. Melanocytes and kerat inocytes were also injured in the epidermis; however, the epidermis re covered completely. No scarring was observed.