Evaluation of a model of bruising in pigmented skin for investigating the potential for alternate light source illumination to enhance the appearance of bruises by photography of visible and infrared light.

The purpose of this study was to evaluate the ability of alternate light source illumination to enhance bruises in pigmented skin. Previous work was limited to simulating bruises in non-pigmented (Caucasoid type) skin by injecting blood into pigskin. In this study, it was investigated if adding a layer of melanin to the surface of the skin would simulate pigmented skin. The study included evaluating the use of a filter that transmitted infrared light (wavelength greater than 720 nm) in place of the recommended visible light filters for the alternate light sources. The results obtained using pigskin with a layer of melanin were almost the same as results using the naturally pigmented goat ear. This indicated adding a layer of melanin could be used as a model for pigmented skin in this simulation of fresh bruising. Comparing the pigskin without melanin with pigskin with melanin revealed that the optimal light source to enhance the appearance of bruising, simulated by injection of blood, changed from violet to blue-green. Using the infrared transmitting filter resulted in greater enhancement than using the alternate light sources with their recommended visible light filter. The advantage of using the infrared transmitting filter was greater with the pigskin coated with melanin and the naturally pigmented goat ears than in the non-pigmented pigskin, however, the results remain to be validated using real bruises in naturally pigmented human skin.