Comparison study of a Q‐switched alexandrite laser delivered with versus without compression in the treatment of dermal pigmented lesions

BACKGROUND: The Q-switched laser is the treatment of choice when attempting to improve dermal pigmented lesions. However, purpura and dyspigmentation are frequently observed after treatment. OBJECTIVE: To compare the efficacy and complications of the Q-switched alexandrite laser when delivered with versus without compression in the treatment of dermal pigmented lesions. METHODS: Ten patients with dermal lesions were enrolled in the study. Each patient had a lesion treated with the Q-switched alexandrite laser delivered with compression. Each patient also had a lesion treated with the Q-switched alexandrite laser delivered without compression with the same fluence and spot size. The patients were evaluated for efficacy and treatment-related side effects. RESULTS: There was no significant difference in efficacy, but purpura and dyspigmentation were more likely when pigmented lesions were treated without compression. CONCLUSION: Purpura from Q-switched laser treatment in darkly pigmented skin is due to mechanical injury of blood vessels. It is well known that pressure 'diascopy' eliminates blood from cutaneous vessels by coapting the vessel lumen. In this study, we used pressure applied by a glass window on the Q-switched laser handpiece to remove cutaneous blood during laser exposure, making it possible to reduce purpura and dyspigmentation.