Design and evaluation of a novel portable erythema-melanin-meter.

BACKGROUND AND OBJECTIVES: Objective evaluation of the pigmentation index (PI) and the eythema index (EI) of human skin is a prerequisite for successful optimization of laser- and intense-pulsed-light (IPL)-based treatment modalities in dermatology. STUDY DESIGN/MATERIALS AND METHODS: We describe a three-wavelength technique for determining PI and EI as well as its particular implementation using LEDs operating at wavelengths of 560, 650, and 710 nm and a large-area photodiode. The instrument has been evaluated both in vitro and in vivo. RESULTS: In vitro, good correlation between the measured indices and results obtained with commercially available techniques has been observed. In addition, linearity of the PI with melanin concentration in the phantom medium up to 7 x 10(-3) nm(-1) (defined as a slope of the optical density spectrum) has been established. In vivo, feasibility of using the technique for predicting the minimal erythema dose (MED), minimal phototoxic dose (MPD), and the threshold of epidermal damage in a photothermal treatment has been demonstrated. CONCLUSIONS: The data suggest that the technique has a substantial potential as a method of pre-treatment diagnostics for photochemical and photothermal procedures.

In vivo fluorescence spectroscopy of the human skin: experiments and models.

The results of the experimental investigation of autofluorescence spectra of human skin in vivo caused by the UV radiation of the skin and by the external mechanical pressure applied to the skin are presented. These results are compared with results of Monte Carlo modeling of the autofluorescence of the skin with variable blood content. The proposed simple model of the skin gives the possibility of evaluation of changes of the blood and melanin content within the skin. © 1998 Society of Photo-Optical Instrumentation Engineers.

In vivo evaluation of sunscreens by spectroscopic methods.

BACKGROUND/AIMS: The methods available for testing the efficacy of topical sunscreens have improved considerably in recent years. Nevertheless, so far no simple and rapid test has been proposed to measure in vivo transmission spectra of sunscreens in the UVA region. METHODS: Spectral changes that occur after sunscreen application were measured with a fluorescence spectrometer (LS 50B, Perkin Elmer, UK) equipped with a Y-shape quartz guide for in vivo measurements. Three sunscreens with different protection factors in the UVA range were tested. The excitation-emission maps of human collagen, skin and sunscreens were analysed. RESULTS: As a consequence of the human skin and sunscreen fluorescence map analysis, the optimal spectral regions (both for direct and indirect fluorescence measurements) were detected. In vivo fluorescence and remittance spectroscopy were used to investigate the time dependence in transmission spectra of epidermis with applied sunscreens. We also evaluated the feasibility of in vivo fluorescence measurements for the investigation of the sunscreens'water-resistance. CONCLUSION: The procedure is simple, and values obtained can be used to predict UVA protection on the basis of the mathematical algorithms.