The primary goal of the dermatologic laser surgeon is to deliver effective treatments without compromising patient safety. Laser and light-based technologies continue to evolve at a torrid pace, whereas the methodology by which laser surgeons assess the skin to be treated has lagged behind.
Fitzpatrick's eponymous skin-typing scale was introduced in 1975 to aid in determining therapeutic UVA light doses for oral methoxsalen photochemotherapy in white patients typed I to IV (Fitzpatrick TB. J Med Esthet. 1975;2:33034). Later expanded to include darker skin types, his system is a subjective assessment based on genetic disposition (eye, hair and skin color as well as freckling), tanning habits and reaction to sun exposure that, when combined with the laser surgeon's therapeutic experience, dictate device treatment parameters (Fitzpatrick TB. Arch Dermatol. 1988;124(6):869-871).
The majority of these products utilize reflectance spectroscopy, which operates on the premise that two main chromophores contribute to skin color - melanin and hemoglobin. Light is delivered to the target surface via a probe and a photodetector is used to collect the reflected light. The more melanin in the skin, the less light reflected. However, in order to account for the contribution of hemoglobin, more than one spectral band must be assessed (Stamatas GN, Zmudzka BZ, Kollias N, Beer JZ. Pigment Cell Res. 2004; 17(6):618-626).