Two lasers, equal results for atrophic acne scars — one is easier to sit through

Design

prospective randomised split-face trial, three sessions at four-week intervals, 20-week duration

Population

27 patients with atrophic acne scars

Primary outcome

ECCA grading scale and Investigator's Global Assessment, with patient-rated improvement, satisfaction and daily adverse reaction diaries

Effect

both devices improved scores significantly (p<0.001) with no significant difference between them; higher satisfaction (p=0.035), shorter erythema and oedema and no crusting with the picosecond laser

Twenty-seven patients with atrophic acne scars had three split-face sessions at four-week intervals, one side treated with a 755-nm picosecond laser with a diffractive lens array and the other with a 1565-nm nonablative fractional laser, then were followed at one, two and three months after the last session. Scarring was scored with the ECCA scale and Investigator's Global Assessment, alongside patient-rated improvement and satisfaction, with adverse reactions recorded daily by patients until they resolved.

Both sides improved significantly on every efficacy measure, and neither was better than the other. The difference was in what the treatment cost the patient: the picosecond side had shorter erythema and oedema, no crusting at all, and higher satisfaction.

The split-face design is the strength here, since each patient is their own control and confounding by skin type and severity disappears. Twenty-seven patients is small, blinding of the patient is impossible when downtime differs, and three months of follow-up will not show late collagen remodelling, which usually favours fractional devices. Even so, if both devices are available, this supports offering the picosecond laser to a patient for whom downtime or the risk of post-inflammatory hyperpigmentation is the deciding factor - which, in Indian skin types IV and V, is most of them.

• Where efficacy is equal, let downtime and pigmentary risk decide the device
• Absence of crusting matters most in skin of colour, where crusting precedes post-inflammatory hyperpigmentation
• Counsel that three sessions at four-week intervals is the minimum course, not a single treatment
• Follow-up here stops at three months; late remodelling with fractional devices is not captured
• Set expectations on the ECCA scale rather than on photographs alone

The statistics, in plain English

The efficacy p-values below 0.001 describe improvement from baseline on each side, not a difference between the two devices; between-device efficacy comparisons were not significant, which in 27 patients means no difference was detected rather than none exists. The satisfaction difference (p = 0.035) is a patient-reported outcome in an unblindable trial, so it partly reflects the visible difference in downtime. A split-face design removes between-patient confounding but cannot exclude carry-over effects between adjacent facial areas.

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