PracticalDermatology

Acne scars, present in 11-14 percent of the adult population, affect patients regardless of age, ethnicity, or sex. There are multiple well–established therapeutic options for acne scars, including laser resurfacing, chemical peels, needling, dermabrasion, and subcision. The 10,600nm CO₂ ablative laser is one of the most widely used treatment options for acne scars and has been shown to be one of the most efficacious lasers for their treatment. The 585nm or 595nm pulsed dye laser (PDL) targets oxyhemoglobin, and can be used to treat erythematous, atrophic, hypertrophic, and keloidal scars. Ablative lasers are generally considered to provide the greatest improvement of atrophic scars, while fractional lasers provide a compromise between clinical improvement and adverse effects. Non–ablative lasers are often considered for hypertrophic, erythematous, or mild atrophic scars. The combination of laser modalities can also be used to improve results, as exemplified in the following case.

CASE Report

An 18-year-old male with Fitzpatrick type IV presented to the dermatology clinic with a history of acne and erythematous rolling, icepick, and boxcar acne scars. In addition to the treatment of his active acne, he was also treated with three sessions of PDL (7mm spot; 8–9mJ; 6ms), fractional CO₂ laser (FCL; 15–20W; spot pitch: 600–800; dwell time: 600–1000; 1 pass), and trichloroacetic acid (TCA) CROS (50%) at four to eight week intervals. Following treatment, the patient’s acne cleared, the scars faded in both number and depth, and all associated erythema had resolved (Fig. 1).

Fig. 1: Patient before (left) and after treatment.

5–YEAR REVIEW OF THE LITERATURE

Over the last five years, there have been several advances in therapeutic laser options for acne scars, including comparisons of existing lasers and alternatives for acne scars, new potential adjuvant therapies, as well as evidence regarding the concomitant use of isotretinoin and laser therapy. Importantly, most of the recent developments have been in skin of color, with 25, 21, and eight of the 32 studies published between 2016 and 2021 explicitly including type III, IV, and V skin, respectively.

Existing lasers. In a prospective cohort study, FCL was shown to reduce the ECCA score by 45.4 percent. The ultra-pulse CO₂ laser, using the manual fractional thermal contraction technology technique reduced the ECCA score by 32 percent after one to four bi-monthly treatments in a prospective trial. In another prospective trial of acne scars in the setting of rosacea, a non–ablative fractional 1440nm laser reduced the ECCA score by 30 points after three monthly treatments. The fractional 1064nm Nd:YAG picosecond laser improved scarring in 85 percent of patients based on the FASQoL questionnaire score by an average of three points after three treatments in another prospective study.

A randomized split-face trial in Asian patients revealed treatment with 1064nm Nd:YAG picosecond laser using a diffractive optical element reduced the ECCA score by 54.6 percent, significantly more than the 41.9 percent reduction in the 1550nm erbium-glass fractional laser group. In a randomized split-face trial, the Nd:YAG picosecond laser and the fractional 1550nm erbium fiber laser reduced ECCA scores by 38.89 and 33.33 percent, respectively, after four monthly treatments. Importantly, more pinpoint bleeding was noted with the picosecond laser, while pain scores were higher with the erbium fiber laser. The 755nm picosecond Alexandrite laser, in a randomized split-face trial of 16 patients, reduced the ECCA score by 24.7 percent following three treatments at four-week intervals. In another randomized split-face trial, treatment with FCL or fractional picosecond 1064nm laser resulted in comparable physician improvement scores for skin texture and atrophy, while the FCL group experienced more post-inflammatory hyperpigmentation. Finally, in a randomized trial, the 2940nm Er:YAG laser in microlaser peel mode, fractional ablative mode, and combined mode, each significantly reduced ECCA scores, with combined mode exhibiting the greatest score reduction; exact reductions are not explicitly stated.

Laser alternatives. In one trial, four treatments with FCL at four-week intervals reduced the ECCA score to a greater degree than three fractional radiofrequency treatments followed by one FCL treatment. In another, one injection of autologous adipose-derived stem cells was comparable to three FCL treatments at four-week intervals for reduction in acne scar area. In a randomized trial, two monthly treatments with fractional Er:YAG laser resulted in a greater reduction in ECCA score than two monthly treatments with bipolar radiofrequency combined with diode laser. In another randomized trial, fractional Er:YAG resulted in clinical improvement in more patients than microneedling with lower pain scores, although downtime was longer. In another study, radiofrequency microneedling (FMR) improved subjects’ subjective evaluation of their acne scars to a greater degree than the 1450nm diode laser. Additionally, another found that while both FMR and ablative fractional Er:YAG laser both effectively treat acne scars, FMR tends to have a shorter downtime and is better tolerated by patients.

Adjuvant therapies. One randomized split-face trial, utilizing the Antera scoring system, determined that FCL in combination with intradermal platelet-rich plasma (PRP) resulted in more patients with good or excellent improvement than FCL alone. Another found that FCL in combination with intradermal PRP resulted in a greater improvement in the 5-point Investigator’s Global Assessment (IGA) as well as ECCA scores than FCL alone. A third study determined that FCL followed by lyophilized PRP treatment increased rates of improvement of skin texture, pigmentation, and pore size compared to FCL alone. Another randomized split-face study found that FCL followed by intradermal PRP improved acne scar appearance by a physician’s assessment to a greater degree than FCL alone. Finally, in a trial comparing the pairing of FCL with either intradermal PRP or non–crosslinked hyaluronic acid, both adjuvant therapies similarly improved Goodman and Baron’s grading system scoring. Topical adipose tissue stem–cell-derived exosomes following FCL, in another trial, reduced ECCA score to a greater degree than FCL alone. In another randomized split-face study, 1550nm erbium glass fractional laser, when followed by FMR was found to improve the ECCA score to a greater degree than the laser alone.

One randomized split-face trial determined that 830/590nm light-emitting diodes low-level light therapy (LED-LLLT) reduced the average duration of post-treatment erythema following FCL. Two randomized split-face trials determined that post-laser application of MAS063DP or a moisturizer containing 5% panthenol, madecassoside, and copper-zinc-manganese are both comparable to 0.02% triamcinolone acetonide regarding reduction in downtime. Silicone gel, applied after treatment with Er: YAG laser in a randomized split-face trial, did not improve physician or patient evaluation of acne scar severity over placebo, although it did improve skin roughness via Visioscan measurement. Β–glucan, in a split-face trial following either FCL or 1565nm non-ablative fractional laser, improved hemoglobin index, skin hydration index, and transepidermal water loss at post-laser day 7. Finally, a randomized controlled trial revealed that 0.05% ECa 233 gel, an extract of Centella asciatica, following 2940nm Er:YAG laser, reduced mean erythema index, as well as physician-scored erythema, crusting, and wound appearance. A randomized controlled trial comparing fusidic acid cream to erythromycin ointment for seven days following FCL found that at both eight and 12 weeks, the fusidic acid group had lower Hyperpigmentation Activity and Severity Index (HASI) scores.

Laser therapy and concomitant isotretinoin use. In an observational study of patients on 0.2–0.3mg/kg/day of isotretinoin, treatment of acne scars with a 650 microsecond, 1064nm Nd:YAG laser, resulted in a 72.2 percent decrease in IGA score and 72.3 percent reduction in Dermatology Life Quality Index (DLQI) while being well tolerated by patients and without formation of new scars. In a randomized split-face study, patients receiving 10mg/day isotretinoin underwent three sessions of 1550nm non-ablative fractional laser, which resulted in improvement of atrophic scar appearance and often mild side effects, including transient erythema and edema. However, additional scar formation was not observed. Another randomized split-face study determined that within one month of completing a course of low dose oral isotretinoin, treatment with 1550nm erbium-doped fiber laser resulted in physician-scored improvement of scar appearance as well as normal wound healing without hypertrophic scar or keloid formation.

Recent Progress

Importantly, most of the studies analyzed laser treatment in skin of color, which is more prone to post-inflammatory hyperpigmentation following laser treatment. The last five years have provided evidence for both additional lasers and alternatives, particularly picosecond lasers and FMR, that can be safely and effectively used to treat acne scars. Additionally, although more data is needed, early evidence suggests that both concomitant and recent isotretinoin use are safe and effective with certain non-ablative lasers. With evidence suggesting the benefits of adjuvant therapies, particularly intradermal PRP, and with new potential alternatives for topical steroids, the last five years have progressed toward improving clinical outcomes, while reducing downtime and minimizing side effects.

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