ABSTRACT
Quantitative phototoxicology requires appropriate dosimetry. The important concepts, terminology, and units of optical dosimetry required in photobiology are all too frequently not fully appreciated in experimental studies, leading to needless misinterpretation and error. The objective of this chapter is to familiarize scientists working in photodermatology with the basic concepts related to light measurement and light source characterization that are necessary for reproducible scientifi c tests. Hopefully this chapter will encourage the reader to look differently at the optical source being used and how correctly to express the exposure dose. Phototoxicological studies require knowledge of the optical and radiometric parameters of ultraviolet optical sources and geometrical exposure factors. This knowledge is required to accurately determine the irradiances (dose rates). In performing any phototoxicity study, it is imperative that the spectral characteristics of the optical source must be known. For a specifi c photobiological action spectrum, different light sources delivering the same optical power can produce completely different dermatological effects if the sources have differing spectra (Figure 63.1). Indeed, a photodermatologist will choose a specifi c ultraviolet (UV) source to match best a given biological action spectrum (if known) to achieve the greatest effi ciency in delivering a photobiologically signifi cant dose. Different applications require different light sources and a variety of measurement techniques may be in order when attempting to conduct different types of studies.
