Skin color and tissue thickness effects on transmittance, reflectance, and skin temperature when using 635 and 808 nm lasers in low intensity therapeutics

Abstract

Skin color and skin thickness affect transmittance and reflectance of laser light and must be accounted for when selecting energy dose to ensure therapeutic effectiveness at the target tissue. Skin heating appears not to be a concern when using 635 and 808 nm lasers at energy doses of up to 12 J and irradiance within American National Standards Institute standards. Photobiomodulation therapy should never exceed the American National Standards Institute recommendation for the maximum permissible exposure to the skin. Lasers Surg. Med. 50:291-301, 2018. © 2017 Wiley Periodicals, Inc.

Microcirculatory Response to Photobiomodulation—Why Some Respond and Others Do Not: A Randomized Controlled Study

“…It is well‐established that NIR light has greater penetration of depth compared with red light [46], which might explain the superior effects on the microvascular response found in this study. The differences in reflectance and transmittance between wavelengths were also found to be modified by skin color, particularly dark versus light skin [47]. In the current study, all participants were relatively light‐skinned and therefore skin color does not seem to be a reason for the difference found between the individuals.…”

Differential response of human dermal fibroblast subpopulations to visible and near‐infrared light: Potential of photobiomodulation for addressing cutaneous conditions

“…At 450 nm wavelength, already along the path from the top of the papillary dermis (100 mm depth) to the bottom of the reticular dermis (1,000 mm depth), light will be strongly attenuated: while 80% of the input photons will reach the top of the papillary dermis, only 10% will interact with the bottom of the reticular dermis [71]. The attenuation of light will naturally depend on the skin type and individual physiology [72,73]. This is an important consideration to take into account when attempting to apply optical treatment parameters found effective in vitro to an ex vivo or in vivo model.…”

Portable and wireless imaging of dorsal hand vein

“…This may be explained by the differences melanosome distribution, which may be found in abundance in darker skin type [19][20]. This light absorbing chromophore reduced the reflectance of light, rendering a lower signal intensity being detected [21]. This similar trend was observed in the computed MSE values, but in opposite manner.…”