LAUSR

light delivery system (Excilite ; DEKA Medical Lasers, Florence, Italy) was used directly towards participants’ left inner forearm as high irradiance (HI) UVB radiation (50 mw/cm). For participants’ right inner forearm treated with low-irradiance (LI) UVB radiation, a neutral density physical filter capable of 75% irradiance reduction was placed in front of the irradiation handpiece of the same excimer light device. The light spectrum and the effect of filter are shown in Figure 1. The exposure time of LI UVB is four times the duration of HI UVB, so the exposure doses were identical. No significant difference in the MED results was observed between the HI and LI UVB-treated areas (P = 0.877) (Table 1b). This result indicated that UVB-induced erythema depends on fluence delivered regardless of irradiance of UVB in both the mouse and human skin. Taken together, at equivalent exposure dose, difference in wavelength is likely the only explanation for the MED discrepancy observed between the different excimer light devices. The declaration of “monochromatic 308 nm in wavelength” regarding those products is perhaps not completely accurate. It is possible that VTRAC excimer light contains a larger proportion of short-wave UVB than TheraBeam excimer light therefore causing a stronger erythemogenic effect at given fluence. We proposed that MED results defined with a particular phototherapy device cannot be used for other devices, even if both devices claimed to be monochromatic (i.e., 308-nm excimer) light. The discrepancy in wavelength, but not irradiance, may play a crucial role in the MED variability. Repeating MED testing before switching to a different phototherapy device is necessary to avoid the risk of burn. The therapeutic effects of similar phototherapy devices may not be reproducible if not all the parameters, including wavelength, irradiance, and fluence delivered, are identical. Shiang-Yu Yang , MD Yi-Wen Liu , MD Cheng-che Lan *, MD, PhD Department of Dermatology, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan Departments of Medical Imaging and Radiological Sciences, College of Health Sciences, Kaohsiung Medical University, Kaohsiung, Taiwan Department of Dermatology, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan *E-mail: [email protected]