Fractional laser benefits differ in treating acne scars in Asian skin
The study was performed at the Tokyo Women's Medical University, Tokyo, where Dr. Kono is chief of the laser unit and assistant professor, department of plastic and reconstructive surgery. It enrolled 16 patients with Fitzpatrick skin types III to IV. Seven patients were treated with only the fractional 10,600 nm CO2 laser (Fraxel re:pair, Solta Medical), six patients were treated with only the fractional 2,790 nm Er:YSGG laser (Pearl Fractional, Cutera), and the two lasers were used in a split-face comparison in three patients.
All patients received a single session of treatment. Settings for the fractional CO2 laser were 40 mJ to 50 mJ for fluence with a density pattern of 8 (30 percent); for the Er:YSGG laser, the fluence was 160 mJ to 200 mJ and the density pattern was set at 4 (16 percent) or 5 (32 percent).
COMPARING RESULTS The two lasers performed similarly for improving appearance of the acne scars. However, the rate of postinflammatory hyperpigmentation (PIH) was significantly higher after treatment with the fractional Er:YSGG laser (66 percent) compared with the fractional CO2 laser (30 percent). In addition, the fractional Er:YSGG laser treatment was uniquely associated with the appearance of dot-like depressions in the skin.
"A number of studies have investigated various fractional lasers for resurfacing procedures. In Asian patients, there is particular concern about the risk for postinflammatory hyperpigmentation (PIH), but there is little information about the relative efficacy and safety of different fractional lasers in this population. Comparative studies such as this can help to identify preferred treatment modalities and settings that can deliver the best results with the least complications," Dr. Kono says.
"Our study indicates the fractional CO2 laser protocol we used is safe and effective for treating acne scars in Asian skin. However, it would be better to modify the parameters of the fractional Er:YSGG laser by reducing the density and/or fluence to minimize the adverse effects," he adds.
Dr. Kono also says patients did not use any bleaching agents pre- or postoperatively.
"Our longest follow-up was to six months. PIH improved over time, and particularly with the use of bleaching agents," he says.
DENSITY LEVELS Dr. Kono says the density levels for the two lasers were chosen so that they would result in similar coverage, and the individual energy levels were also selected so that the depth of penetration would be nearly the same for the two devices. However, the CO2 laser uses a roller pattern while the Er:YSGG laser has a stamp pattern, and the CO2 laser has a smaller spot size than the Er:YSGG laser — 120 microns versus 300 microns, respectively.
"The relatively high-density treatment using a stamp pattern with the fractional Er:YSGG laser seems to increase the risk of hyperpigmentation, while the risk for developing the visible tiny holes in the skin after treatment with the Er:YSGG laser may be attributed to the combination of the relatively high energy with a larger spot size," Dr. Kono says.
All of the procedures were performed using topical anesthesia (7 percent lidocaine cream) and with parallel air cooling (Zimmer Chiller, LaserMed). Ice packs were applied post-treatment, and all patients used an antibiotic ointment for postoperative care.
PATIENT RATINGS Patients were asked to rate treatment discomfort using a visual analogue scale (VAS) of 0 to 10. Despite the modalities used to improve tolerability, the VAS results showed that both laser procedures were moderately uncomfortable (mean VAS scores, CO2 laser, 6.0; Er:YSGG laser, 6.3).
Patients initially returned for asses sment of healing at one week, and no difference was seen between groups in the time to recovery. Subsequent follow-up visits were conducted at one and three months post-treatment. Efficacy was judged by two blinded plastic surgeons based on their assessments of pre- and post-treatment standardized photographs (Visia CR, Canfield Scientific).