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In the past reports, excessive or long-term ultraviolet (UV) irradiation may cause DNA damage, resulting in genetic mutations and probably leading to skin cancer. However, it is difficult to noninvasively diagnose skin damage in the early stage due to excessive and long-term UV exposures. In this study, we propose to use optical coherence tomography (OCT) for noninvasively investigating the progress of skin damage due to excessive UV irradiation. The developed OCT system can provide the ability of label-free 3D microstructural and microvascular imaging with the axial and transverse resolution of 7 and 5 m, respectively. Mouse skin is used as the experimental model and exposed to different UV exposure powers of 5, 20 and 50W (corresponding to the power densities of 1.6, 6.4, and 16 W/cm2) for various time periods. The results show that the morphological and microcirculation changes can be identified when the skin is exposed to different exposure powers. With a lower exposure power of 5 W, no significant structural change can be found from the OCT results, but the vessel sizes are slightly increased and the vessel density is also increased. When the exposure power of UV light is increased to 20 W, the vessel density is increased significantly with the exposure time and the structural damage is also can be found. Then, when mouse skin is exposed to a higher UV power of 50 W for 8 mins, the skin structure and vessels are severely damaged. Finally, the skin after the exposures of various UV powers is also followed up with OCT to evaluate the skin recovery. The results show that the structural and microvascular changes due to UV irradiation can be identified with OCT and OCT can be an effective and noninvasive diagnostic tool for the early-stage sun damage.
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