Polarization enhanced wide-field imaging for evaluating dermal changes caused by non-ablative fractional laser treatment.

Background And Objective: Laser non-ablative fractional treatment (NAFT) is an important part of armamentarium of modern dermatology. Recently, such treatments have become available in at-home setting due to advent of self-application NAFT devices. Safety and clinical efficacy of NAFT are well established in multiple studies. Less information is available on morphological and functional changes in tissue occurring as a result of NAFT. Polarization-enhanced multispectral wide-field imaging device allows for in vivo real time visualization of dermal structures. The objective of this study is to use this imaging modality to monitor early effects of the home-use NAFT on collagen networks.

Materials And Methods: Eight subjects (skin types I-III) used a commercially available NAFT device (wavelength 1410 nm, energy per pulse up to 15 mJ) to treat peri-orbital wrinkles in standard recommended mode, that is daily, for a period of two weeks. In each session, subjects applied a pre-treatment gel to the peri-orbital areas and then used the device, delivering 8-10 applications to each side of the face without overlap. Subjects were asked to use the highest device setting. Cross-polarized 440 nm wide-field images were acquired from peri-orbital areas before and two weeks after the onset of the treatment regimen. Wide-field images were normalized and thresholded to a level of 40% brightness to emphasize collagen structure. Collagen content was quantitatively determined from thresholded collagen images. Improvement in collagen content at two weeks of daily treatments was assessed.

Results: Eight subjects (age 24-53 years) completed the study. Cross-polarized 440 nm wide-field images clearly delineated collagen networks. Quantitative assessment of collagen images revealed statistically significant (P < 0.05) improvement of collagen content at a time point of two weeks. Seven out of eight subjects showed varying degree of improvement. The increase of collagen content in responders ranged from 1-26%, with the mean improvement of 11%. Subjects in their early 40s showed the best improvement in comparison to younger and older age groups.

Conclusions: Polarization-enhanced multispectral wide-field reflectance imaging method is a suitable technique for noninvasive in vivo assessment of dermal structures. Post-treatment images, taken three days after the last treatment session, demonstrate that non-ablative fractional treatment resulted in increased dermal collagen content as measured by the polarization-enhanced technique as early as two weeks post onset of the treatments. However, further studies with a larger number of subjects and longer treatment period are required to determine the optimal regimen and how long the results will last.