Table 2.
Devices available to calculate epidermal melanin concentration (EMC) in skin. Tristimulus reflectance colorimetry quantifies the amount of light reflected through three broad wavelength filters and describes the colour using of three coordinates (XYZ) that are typically converted into other colour systems such as RGB and CIELAB (Van Der Wal et al. 2013)
| Device | Technique | Development and commercial availability | References |
|---|---|---|---|
| DRS probe (R200-7-UV-VIS, Ocean Optics, 830 Douglas Avenue, Dunedin, FL) |
Diffuse reflectance spectroscopy utilising a white light source, optical fibre and spectrometer, and measures the light diffusely reflected by the skin. Values for melanin and erythema are given in mol L−1 |
Commercially available probe | (Wright et al. 2016) |
| CM-2600d (Konica Minolta, Japan) | Remittance spectroscopy at 390 nm at a 15-nm bandwidth with an 8-mm aperture | Commercially available handheld spectrometer | (Verkruysse et al. 2009) |
| iPulse (CyDen Ltd., Swansea, UK) | Remittance spectroscopy at 460 nm | Preproduction handheld prototype consisting of three main components: an optical head, a control and data processing unit, and the power supply unit | (Ash et al. 2015) |
| DSM II and DSMIII ColorMeters (Cortex Technology ApS, 9560 Hadsund, Denmark) | Narrowband tristimulus reflectance spectrophotometry (470, 510 and 660 nm) with a 4 mm aperture. Can directly measure erythema, EMC and CIELAB values | Commercially available handheld colorimeters | (Ash et al. 2015; Van Der Wal et al. 2013) |
| Custom-built photothermal detector device with a PVI-5 probe (Boston Electronics, Boston) and Gentlelase Alexandrite laser (Gentlelase, Candela, Wayland, MA) | Photothermal measurements using an uncooled photovoltaic infrared photodetector PVI-5 probe (spectral bandwidth 2.5 to 5 μm, HgCdZnTe) that was aligned with the hand-piece of a Gentlelase Alexandrite laser (755 nm, 3-ms pulse duration) | Novel custom-built handheld device with a probe that was calibrated prior to each measurement with a commercial blackbody (BB701, Omega) | (Verkruysse et al. 2009) |
| Mexameter (MX18 probe) (Courage-Khazaka, Germany) | Narrowband tristimulus reflectance spectrophotometry (568 nm, 660 nm and 870 nm). Calculates erythema and melanin index values using an arbitrary scale ranging from 1 to 1000, with higher erythema and melanin index readings denoting more erythematous and darker skin or scar. Has a 5-mm aperture | Commercially available as a standalone device or as a MX18 probe that is connected to the company’s phototherapy device | (Bhargava et al. 2016; Matias et al. 2015; Van Der Wal et al. 2013) |
| Colorimeter (CL 400 probe) (Courage-Khazaka, Germany) | Tristimulus reflectance colorimetry using wavelength emissions ranging from 440 to 670 nm. The device interprets reflected light from white light-emitting diodes (LED) expressed in CIELAB system (represented as LAB1, LAB2 and LAB3, respectively) and individual typology angle (ITA) index values | Commercially available | (Matias et al. 2015; Van Der Wal et al. 2013) |
| CR200b and CR-400 chromameters (Minolta, Osaka, Japan) | Tristimulus reflectance spectrophotometry (450, 560 and 600 nm). The Minolta chromameter allows skin colour to be evaluated as a set of three parameters L, A and B in the colour space of CIELAB-system. | Commercially available | (Dolotov et al. 2004) |
| Custom EMM-01 device with three principle components: the optical head, the control/data processing unit and the power supply unit | Tristimulus reflectance colorimetry (560, 650 and 710 nm) | Novel and portable erythema/melanin meter device | (Dolotov et al. 2004) |
| Dermacatch photodetector | Visible-spectrum reflectance colorimeter (full visible light spectrum emission) that measures globally reflected light to compute erythema as well as melanin values (with arbitrary units). The measured area covers a disk of 5.5 mm in diameter | Commercially available | (Baquié and Kasraee 2014) |
| TLS850 Translucency Meter (Dia-Stron, Hampshire, UK) | Reflectance spectrophotometry that can be used to calculate the melanin index using the formula: melanin index = log10(905 nm/632 nm) × 1000 and the erythema index. The manufacturer reports the device’s fibre optic faceplate is insensitive to surface optical effects and only interprets internally scattered light. Measurements can be carried out using single colour modes of red, green or blue from the emission source | Commercially available reflectance spectrophotometer | (Ha et al. 2003; Kuchel et al. 2002) |