Optical Characteristics of the Skin with Dark Circles Using Pump-Probe Imaging

Pump-probe imaging is a noninvasive optical imaging technique that can sensitively and specifically detect melanin in the skin with dark circles. This study aimed to obtain microscopic images and spectral information of melanin granules in ex vivo lower eyelid skin tissues using pump-probe imaging, to compare the distribution characteristics and difference in the content of melanin granules. Specimens of ex vivo human skin with dark circles obtained from patients undergoing blepharoplasty were examined. All tissue sections were analyzed using a nonlinear pump-probe imaging system and ferrous sulfate (FeSO4) staining. These two imaging methods of melanin were compared based on the intraclass correlation coefficient (ICC). Subsequently, the distribution of melanin granules was investigated, and the melanin content index (MCI) and the mean fluorescence intensity (MFI) were quantitatively analyzed simultaneously. Results showed that different types of the skin with dark circles and normal skin were significantly different in the distribution of melanin granules, which can be used to distinguish the skin with dark circles from the normal skin, guide treatment, noninvasively evaluate clinical treatment, and track the progress of dark circles or other pigmentation diseases