Confocal laser microscopy of the in vivo human skin revisited.

A new generation of confocal laser microscope, designed to image the human skin in vivo, improves the resolution, contrast and spectroscopic facilities as compared to the previous Tandem Scanning Microscope (TSM) prototype. The new device has been built with a Oz module (Noran) equipped with the skin contact device, assuming a perfect stability of skin images in the horizontal plane. The Z displacement of the objective lens, mounted directly on the Ch module, is assumed by a piezo motor with a course of 350 mu m. Moreover, the Ch module has been suspended on articulated arms to reach any part of the human body. The power of the Argon/Krypton laser source has been limited to 2 mW to secure safety and provides three visible wavelength : 488, 568 and 647 nm. The facility of instantly checking wavelength during in depth exploration of the skin optimizes the resolution and contrast of images as compared with the white light used in the TSM. Consequently, better image quality of the epidermis is obtained in the blue region with unexpected details of corneocytes and keratinocytes. The papillary dermis comprising the vascular network is advantageously observed with the red light. The fluorescence channel detector gives additional information on the penetration of fluorescent probes through the skin barrier. Optical sections are digitized (512 x 480 x 8 bit) at video rate, providing easy and fast measurements of the thickness of epidermal layers. The Silicon Graphics workstation generates a transparent volume of living human skin in less than 5 minutes. This powerful and convivial new design for imaging the in vivo human skin opens up new promises in skin research and in vivo skin pharmacology.