Page 166 - Blog Posts v1

'Fitzpatrick 1' - although, the Fitzpatrick scale is NOT a skin colour scale!!!). SC2 is 10%, SC3 is 16%, SC4 is 23.5%, SC5 is 33% and SC6 is 43%. These concentrations represent the change in skin colour due to melanin alone.
Figure 2: The relative absorptions in three skin colours (1, 3 and 6) and in oxyhaemoglobin with light from the Nd:YAG (532 & 1064nm), ruby, diode and alexandrite lasers
Figure 2 shows the relative absorptions of five wavelengths commonly used in laser skin treatments today, in three skin colours and haemoglobin. The skin colours I chose are SC1, 3 and 6 - which ranges from very pale skin (5% melanin concentration) to black skin (43% concentration). Obviously, the darker skin colour absorbs much more light energy than the lighter colours. This is not surprising since the higher concentration of melanosomes will obviously absorb more light. We can also see that the 532nm wavelength is the most strongly absorbed wavelength in all skin colours - again, this is not surprising since 532nm is more strongly absorbed than all the other, longer wavelengths (see figure 1). While, the order of absorption is ruby, alex, diode followed by 1064 Nd:YAG, in all cases. Again, given the curves in figure 1, this is not surprising.
The last set of bars on the right of figure 2 shows the relative absorptions in blood. Once again, the 532nm wavelength dominates over all the others, in terms of absorption. Interestingly, the order of the other wavelengths is the reverse of that in melanin - Nd:YAG, diode, alex and then ruby. But these are all miniscule compared with the 532nm light!
All the bars in figure 2 are on the same scale. So, that means that they can all be compared against each other. This shows that the absorption of 532nm is almost the same in black
Mike’s Blog Posts 166