Kim 2009.

Methods	A split‐face trial conducted in patients with acne scars. Facial halves were randomly assigned to receive either treatment
Participants	20 participants (6 women and 14 men) aged 22 – 37 years with mild to moderate acne scars and Fitzpatrick Skin Types IV and V. The participants were grouped as rolling type group and icepick type group according to the predominant scar type Exclusion: "Pregnancy or lactation, history of hypertrophic scarring or keloid formation, history of active or recurrent herpes simplex, presence of infected skin lesions, refusal to give signed informed consent, and use of isotretinoin within 6 months before treatment"
Interventions	Intervention: 1 facial half received treatment with 1550 nm Er:Glass fractional laser (Mosaic1, Lutronic Corporation, Gyeonggi, Korea). The 1550 nm Er:Glass fractional laser applied pulse energy of 30 – 32 mJ and density of 300 – 350 spots/cm2 using a 6 mm handpiece tip 3 times during a 6‐week interval Comparator: The contralateral half received CROSS method using 100% TCA. The CROSS method repeated 2 times every 12 weeks
Outcomes	Improvement of acne scars (12 weeks), using a quartile scale (0 = no improvement; 1 = 1% – 25% improvement; 2 = 26% – 50% improvement; 3 = 51% – 75% improvement; 4 = > 75% improvement) Participant satisfaction (12 weeks) using the same quartile scale Side effects (12 weeks), including severity of the pain on a 10‐point scale (0 – 9), erythema lasting days, and overall down time Timing: at baseline, at week 6, week 12, week 18, week 24,and 12 weeks after the final treatment
Funding source	Yonsei University Research Fund of 2007
Declaration of interest	No available data
Notes	Korea Informed consent was obtained from all participants Study approved by the hospital’s medical ethnic committee
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "Facial halves were randomly assigned" Comment: Insufficient data
Allocation concealment (selection bias)	Unclear risk	Insufficient information about the allocation concealment process to permit judgement
Blinding of participants and personnel (performance bias) All outcomes	High risk	Quote: "One side was treated with the 1,550nm Er:Glass fractional laser .....And the other side was treated with CROSS method " Comment: Probably not done. Given that the control arm was easily distinguished from the treatment arm during treatment, participants and the treating dermatologist were not blinded
Blinding of outcome assessment (detection bias) Investigator‐ assessed	Low risk	Quote: "Patient photographs were reviewed by 2 independent physicians who were blinded to the study." Comment: Probably done
Blinding of outcome assessment (detection bias) Participant‐reported	High risk	Quote: "One side was treated with the 1,550nm Er:Glass fractional laser .....And the other side was treated with CROSS method " Comment: No blinding of participants and the outcome assessment is likely to be influenced by lack of blinding
Incomplete outcome data (attrition bias) All outcomes	Low risk	18/20 participants completed the trial and were included in the data. 1 participant dropped out because of slight discomfort of the treatment such as pain and erythema, and the other dropped out because of scheduling conflicts
Selective reporting (reporting bias)	Low risk	The study protocol is not available but it is clear that the published reports include all expected outcomes that are of interest in the review
Other bias	Low risk	The study appears to be free of other sources of bias