CAMBRIDGE, Mass., Nov. 30 -- The excimer laser is a major advance in psoriasis treatment, according to Kenneth Arndt, MD, clinical professor of dermatology at Harvard Medical School, where it was tested on 80 patients. Arndt said 72 percent of the patients achieved at least 75 percent clearing of their psoriasis with an average of 6.2 treatments, and 84 percent of patients also experienced at least 75 percent clearing after 10 treatments or less. Half of the patients achieved 90 percent improvement after less than 10 treatments. There are many treatments but no cure for psoriasis, a chronic skin condition afflicting six to seven million Americans. Arndt said, "While conventional therapies can still be successful at treating psoriasis, I think the excimer laser will appeal to patients with mild to moderate conditions who have given up therapy because they found other treatments to be too messy, ineffective or expensive." The excimer laser -- also known as narrow band laser phototherapy -- delivers high-intensity ultraviolet radiation to localized areas of psoriatic plaques. Rather than flood the unaffected skin with ultraviolet light, this laser enables a dermatologist to direct the treatment only to affected areas. Since indirect damage to healthy skin is avoided, this permits much stronger treatment dosages than are possible using conventional ultraviolet B or PUVA treatments.