The development of a filter to enhance the efficacy and safety of excimer light (308 nm) therapy

Abstract

Excimer light (308 nm) therapy is a new ultraviolet (UV) B phototherapy for which the efficacy and resulting DNA damage are not well established. To develop an effective and safe phototherapy using the excimer lamp, we studied the effects of different light cut-off filters, A and B. Efficacy was evaluated by measuring apoptosis using fluorescence-activated cell sorting analysis. DNA damage was evaluated by measuring cyclobutane pyrimidine dimers (CPDs). Light sources, including normal wave and short wave (SW) excimer light, broad-band (BB) UVB, and narrow-band (NB) UVB, were examined using the filters. A human skin equivalent model was also examined. The ratio of positive apoptosis to CPD formation normalized to the mean induced by NB-UVB was 5.7 using the excimer lamp without a filter, 6.3 using the excimer lamp with the A filter, 6.4 using the SW excimer lamp without a filter, and 4.2 using the BB-UVB. The A filter reduced CPD formation induced by the normal wave and SW excimer lamp. In the human skin equivalent model, the use of filters significantly decreased the amount of CPD-positive cells. These findings suggest that using the A filter with the excimer lamp increases the efficacy and safety of excimer light therapy.