Dermatol Surg. 2009 Jun 22; Wanitphakdeedecha R, Manuskiatti W, Siriphukpong S, Chen TMBACKGROUND Treatment of acne scars remains a challenge, especially in dark-skinned individuals. Treatment parameters may be optimized by selecting appropriate pulse width and laser energy that enhance tissue thermal response with limited morbidity. OBJECTIVE To determine the efficacy and side effects of variable square pulse (VSP) erbium:yttrium-aluminum-garnet (Er:YAG) laser resurfacing for treatment of punched-out atrophic and rolling acne scars. METHODS Twenty-four subjects with acne scars were treated monthly for 2 months with four passes of VSP Er:YAG laser resurfacing using a 7-mm spot size and a fluence of 0.4 J/cm(2). Subjects were divided into two groups and treated with two different pulse widths: 300 mus (short pulse, SP) and 1,500 mus (extra-long pulse, XLP). Objective and subjective assessments were obtained at baseline and 1, 2, and 4 months after treatment. RESULTS In the SP group, skin smoothness improved significantly (p
