Excimer Laser for Psoriasis: A Review of Theories Regarding Enhanced Efficacy Over Traditional UVB Phototherapy

Background: Fiber-optically targeted ultraviolet B (UVB) therapy has been shown to clear plaques of psoriasis in a significantly fewer number of treatments and reduce overall cumulative UVB dose than traditional UVB phototherapy. Objective: This article reviews existing theories in the literature attempting to explain the superior efficacy of targeted UVB. Methods: Medline was used to perform a comprehensive review of the literature from 1965 to present. Only information from the English language journals are reported in this study. Results: The theories proposed to explain the higher efficacy of the excimer (XeCl) laser relative to traditional UVB include the ability to use higher intensities of ultraviolet (UV) light and a more efficient induction of T cell apoptosis. Conclusion: The possible explanations for the superior efficacy of the excimer laser over traditional UVB therapy for psoriasis include: 1) a higher intensity UV light to plaques, which is more effective in clearing psoriasis; 2) penetration into the dermis where it may induce T cell apoptosis, potentially to a greater extent than the wavelength or given energy level predicts; and 3) the difference in the delivery of UVB light may result in cell death and skin immune system suppression more effectively than traditional UVB.