ABSTRACT
The erythema index is constructed along the principles set out by Diffey et al. Light of two narrow wavebands is directed on to the skin and the diffuse remittance measured. This diffused light has passed into the upper region of the skin and has been scattered and absorbed by the cutaneous structure and pigments. The Melanin meter is based on the same principle, but uses different wavelengths. It has been found by Edwards et al. that a red and a near infra-red wavelength can be chosen to lie on minima of blood pigment absorbance, giving excellent isolation of the melanin index from the vascular state of the skin. Using the Optomax image analysis system the percentage area of corneocytes occupied by melanin granules was quantified and this figure was used as the Surface Melanin Index.
