Abstract: A fiber optic probe comprises a pair of substantially parallel optical fibers separated by a gap and positioned in a centrifuge tube which contains a stratified medium. The pair of fibers includes a transmit fiber for directing light from a light source into a substantially undisturbed portion of the stratified medium disposed in the gap. Light traversing the portion of the stratified medium in the gap is collected by a receive fiber and provides an indication of a light property of the portion of the stratified medium disposed in the gap. The pair of fibers are adapted to be moved in the stratified medium without significantly disturbing the stratification of the medium. As the fibers are moved, light property measurements can be obtained in other substantially undisturbed portions of the stratified medium.

Abstract: A cutaneous pigmented lesion is treated by irradiation with laser light of between 345 and 600 nm and preferably about 500 nm wavelength. The fluence is between 1 and 10 J/Cm.sup.2 and preferably between 2 and 4 J/cm.sup.2 . The pulse duration is less than 1 .mu.sec and preferably less than 500 nsec. A 3 mm diameter spot is illuminated.