Melanin provides protection against excess exposure to solar ultraviolet radiation (UVR) and related adverse health effects. Diffuse Reflectance Spectroscopy (DRS) can be used to calculate 2 cutaneous melanin and erythema, but this is complex and has been mostly used for light-tomedium pigmented skin. Handheld reflectance spectrophotometers, such as the Mexameter® MX18, can also be used. We compared DRS-calculated melanin and erythema values with Mexameter melanin and erythema index values to understand how these techniques / measurements correlate in an African population of predominantly deeply-pigmented skin. 503 participants comprised 68.5% self-identified Black African, 9.9% Indian/Asian, 18.4% White and 2.9% Coloured. The majority of Black African (45%), Indian/Asian (34%) and Coloured This finding is considered spurious and may result from the complexity of separating brown and red pigment when using narrowband reflectance techniques. Further work is needed to understand melanin, erythema and colour in Black skin given sun-related health risks in vulnerable groups in Africa.

In any laser skin treatment, the optical properties (absorption and scattering coefficients) are important parameters. The melanin content of skin influences the absorption of light in the skin. The spread in the values of the absorption coefficients for the South African skin phototypes are not known. A diffuse reflectance probe consisting of a ring of six light delivery fibers and a central collecting fiber was used to measure the diffused reflected light from the arms of 30 volunteers with skin phototypes I-V (on the Fitzpatrick scale). The absorption coefficient was calculated from these measurements. This real-time in vivo technique was used to determine the absorption coefficient of sun-exposed and -protected areas on the arm. The range of typical absorption coefficients for the South African skin phototypes is reported. The values for the darker South African skin types were much higher than was previously reported for darker skin phototypes. In the analysis, the contributions of the eumelanin and pheomelanin were separated, which resulted in improved curve fitting for volunteers of southern Asian ethnicity without compromising the other groups.

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An individualised laser skin treatment may enhance the treatment and reduces risks and side-effects. The optical properties (absorption and scattering coefficients) are important parameters in the propagation of laser light in skin tissue. The differences in the melanin content of different skin phototypes influence the absorption of the light. The absorption coefficient at the treatment wavelength for an individual can be determined by diffuse reflectance spectroscopy, using a probe containing seven fibres. Six of the fibres deliver the light to the measurement site and the central fibre collects the diffused reflected light. This is an in vivo technique, offering benefits for near-real-time results. Such a probe, with an effective wavelength band from 450 to 800 nm, was used to calibrate skin-simulating phantoms consisting of intralipid and ink. The calibration constants were used to calculate the absorption coefficients from the diffuse reflectance measurements of three volunteers (skin phototypes, II, IV and V) for sun-exposed and non-exposed areas on the arm.

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Laser light is frequently used in both diagnostics and treatment of patients. For any laser treatment to be effective it is important to deliver the correct dose at the treatment site. Human skin scatters and absorbs laser light in the visible wavelength region, which results in a decrease in fluence some distance into the skin. Computer simulations can be used to predict the fluence at the treatment site. Liquid and solid phantoms were prepared and the optical properties were measured. These values were then used as input values to a commercial software package simulating the different layers of skin representing phantoms. The transmission and reflected fractions of the different phantoms were measured with an integrating sphere and compared with the computer simulations. The results showed very good agreement with the measured values and the model can therefore be used with confidence to predict fluence at any treatment site inside the skin.

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