Lasers in Surgery and Medicine

Efficacy and Safety of Ablative Resurfacing With AHigh‐Energy 1,064 Nd‐YAG Picosecond‐domain Laser forthe Treatment of Facial Acne Scars in AsiansYing‐Xiu Dai, 1,2 Ying‐Yen Chuang,3 Po‐Yu Chen,1 and Chih‐Chiang Chen1,2,4*1Department of Dermatology, Taipei Veterans General Hospital, Taipei 11221, Taiwan2Department of Dermatology, School of Medicine, National Yang‐Ming University, Taipei 11221, Taiwan3DRX Dermatology Clinic, New Taipei City 24147, Taiwan4Institute of Clinical Medicine, National Yang‐Ming University, Taipei 11221, Taiwan

Objectives: There have been few studies regarding theuse of a picosecond‐domain laser for acne scars in Asians.This prospective study evaluated the efficacy and safety ofa high‐energy 1,064 nm Nd:YAG picosecond‐domain laserfor ablation and resurfacing of facial acne scars in Asians.Methods: Subjects were treated with a 1,064 nm picose-cond laser (8mm spot, 0.7–1.0 J/cm2, 5Hz) every 4 weeksfor three sessions. Two blinded dermatologists evaluatedthe pre‐ and 3‐month post‐treatment images with a 10‐point improvement scale. Subject pain, global improve-ment, and satisfaction were also assessed. The FacialAcne Scar Quality of Life (FASQoL) questionnaire wasused to evaluate the subjects’ quality of life.Results: Twenty subjects aged 18–50 years with Fitzpa-trick skin type III–V were enrolled. The median derma-tologist‐rated improvement score was 3 out of 10. Subjectswere satisfied to very satisfied with global improvement.Subjects’ quality of life significantly improved with amedian FASQoL score of 10 after treatment comparedwith 21 before treatment (P< 0.001). Adverse effects werelimited to erythema, pain, and edema without postin-flammatory hyperpigmentation.Conclusions: The 1,064 nm picosecond‐domain laserwith ablative resurfacing parameters is safe and effectivefor the treatment of acne scars in Asians. Lasers Surg.Med. © 2019 Wiley Periodicals, Inc.

Key words: acne scars; treatment; fractionated; picose-cond; laser

INTRODUCTION

Acne vulgaris is a common skin disease that can lead topermanent scarring [1–3]. Acne scarring significantlyimpairs patients’ quality of life and has been describedas a risk factor for depression, suicide, low academicperformance, and unemployment [4,5]. The managementof acne scarring depends on the types of acne scars andthe limitations of the treatment modalities [6]. Currenttreatment modalities include chemical peeling, dermab-rasion, needling, filler, platelet‐rich plasma, ablative

lasers, fractional/nonablative lasers, and punch excision[7–14]. Despite the availability of multiple treatmentmodalities, management of acne scars remains challen-ging. The 755 nm Alexandrite picosecond laser with adiffractive lens array has demonstrated clinical efficacyfor improving facial acne scars [15,16]. However, the useof a high‐energy 1,064 nm Nd:YAG picosecond‐domainlaser for ablation and resurfacing of acne scars have neverbeen investigated. In this study, we examined the efficacyand safety of a new 1,064 nm picosecond‐domain fractio-nated laser with a high‐energy setting for the treatmentof acne scars in Asians.

MATERIALS AND METHODS

Subjects

Patients aged 18–50 years with Fitzpatrick skin type III–Vand facial acne scars were enrolled. The Fitzpatrick skin typewas determined by the study investigators based on a sun‐exposure reaction questionnaire and the investigator’sobjective evaluation. To be included, subjects were requiredto have facial acne scars and be otherwise healthy withoutpregnancy, lactation, a history of skin cancer, keloidalscarring, active infection, immunodeficiency disorders, andlight hypersensitivity or taking phototoxic medications.Patients who received resurfacing procedures such as lasertreatment or chemical peels to the face within the previous 6

© 2019 Wiley Periodicals, Inc.

Accepted 11 August 2019Published online in Wiley Online Library(wileyonlinelibrary.com).DOI 10.1002/lsm.23151

*Correspondence to: Chih‐Chiang Chen, MD, PhD, Depart-ment of Dermatology, Taipei Veterans General Hospital, Taipei11221, Taiwan. E‐mail: docs1.tw@yahoo.com.tw

Ying‐Xiu Dai and Ying‐Yen Chuang contributed equally tothis work.

Conflict of Interest Disclosures: All authors have completedand submitted the ICMJE Form for Disclosure of PotentialConflicts of Interest and have disclosed the following: Y.‐Y.C. is aspeaker for Quanta System.

Ethical approval: This study was approved by the InstitutionalReview Board of the Taipei Veterans General Hospital (IRB‐TPEVGH No.: 2018‐02‐004A).

Contract grant sponsor: Ministry of Science and Technology;Contract grant number: MOST 107‐2314‐B‐075‐032‐MY3‐1.

months were excluded as well. This study was approved bythe institutional review board of the Taipei Veterans GeneralHospital (2018‐02‐004A) and informed consent was obtainedfrom all the subjects.

Laser Treatment

A picosecond‐domain, 1,064/532 nm Nd:YAG laser (Dis-covery PICO®; Quanta system S.p.A., Samarate, Italy)was used for all laser treatments. The device is equippedwith a specialized handpiece with micro‐lens array(MLA), which fractionates the laser beam into 66microbeams in an 8mm circular diameter (Fig. 1a). Thelaser system delivers an adjustable energy level, from0.05 to 1.4 J/cm2. The calculated energy level ranges from0.45 to 12.7mJ per microbeam. With a low scattering rate,

the MLA is able to deliver 90% of the set energy in thehigh fluence regions, which cover 5% of the treatment spotin total. Before treatment, each acne scar within thetreatment area was mapped and photographed. Topicalanesthetic cream (EMLA®; AstraZeneca, Wilmington, DE)was applied with occlusion for 40minutes. With a fixedspot size of 8mm, fluence of 0.7–1.0 J/cm2, repetitive rateof 5Hz, and two passes, a 1,064 nm picosecond laser withMLA was applied to all areas of facial acne scars,including rolling, boxcar, and icepick scars. Double laserpasses were administered sequentially in rows, approx-imatively corresponding to 10% surface of the treatmentarea. A total of 1,200–1,600 pulses were given per sessionbased on experience with the laser and tissue reaction.Immediate erythema and mild oozing of bloody serous

Fig. 1. (a) The 66‐microbeam pattern of the 1,064 nm Nd:YAG picosecond‐domain laser withmicro‐lens arrays. (b) There was no significant correlation between subject age anddermatologist‐rated improvement score (Spearman rank ρ=−0.298, P= 0.202). (c) There wasno statistically significant difference in the dermatologist‐rated improvement score between menand women (median [range]: 3.0 [−6 to 8] in men vs. 4.0 [−7 to 8] in women, P= 0.641). Linesindicate median values. (d) Histology showing epidermal ablation (H&E stain, ×40). (e) High‐power view (H&E stain, ×100). (f) A well‐defined, intra‐epidermal vacuole (H&E stain, ×40). (g)High‐power view (H&E stain, ×100). H&E, hematoxylin and eosin.

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exudates, a sign of epidermal ablation, were the desiredendpoints. All subjects received treatment every 4 weeksfor a total of three sessions.

Evaluation of Efficacy

Two‐dimensional photographs (Nikon D640) were ta-ken before the initial laser treatment and 3 months afterthe final treatment session. The photographs were takenin standardized lighting and photography sitting areas.To avoid confirmation bias, two blinded dermatologistsevaluated the photographs in pairs of pre‐ and 3‐monthpost‐treatment randomized to left and right panels. Foreach subject, improvement in volume, texture, and overallappearance of the treatment areas was assessed withbefore‐and‐after photographs. The reviewers were askedto identify which image was the pre‐treatment photo-graph and then rate the degree of improvement using a10‐point global aesthetic improvement scale (1= 10%,2= 20%, 3= 30% improvement to 10= total clearance). Incases where the reviewer incorrectly identified a pre‐treatment photograph, the subject’s evaluation obtained anegative score.At 1 and 3 months after the final treatment, subjects

were asked to evaluate the improvement in overallappearance on a 10‐point scale (1= 10%, 2= 20%,3= 30% improvement to 10= complete clearance). Sub-jects also rated their satisfaction with improvement inoverall appearance and texture on a 5‐point Likert scale(−2= very dissatisfied, −1= dissatisfied, 0= no opinion,1= satisfied, and 2= very satisfied) at 1 and 3 monthsafter the final treatment. To assess the impact oftreatment on quality of life, subjects were asked tocomplete the Facial Acne Scar Quality of Life (FASQoL)questionnaire before the initial treatment and 3 monthsafter the final treatment. FASQoL is a 10‐item instrumentwith three domains assessing the impact of scars onemotions, social functioning, and work/school on a 5‐pointrating scales with a recall period of the past 7 days(0= not at all, 1= a little, 2= somewhat, 3= very much,and 4= extremely) [17].

Evaluation of Safety

Subjects assessed their discomfort after each treatmentsession using the Wong‐Baker Faces Pain Rating Scale(0= no discomfort; 10= intolerable pain). Subjects werealso required to record post‐treatment effect includingerythema, edema, exfoliation, petechiae, and blistering.At 3 months after the final treatment, two blindeddermatologists independently evaluated hypopigmenta-tion, hyperpigmentation, and scarring.

In Vivo Study

An in vivo study was conducted in one male subjectprior to the surgical excision of a deep box scar, which didnot greatly benefit from the laser treatment. The patientreceived the laser treatment 30minutes prior to thepunch excision.

Statistical Analysis

Descriptive statistics were applied to summarize thedata. Comparing different groups was performed usingthe Wilcoxon rank‐sum test and the Kruskal–Wallis test.The Spearman rank correlation coefficient was calculatedon age, improvement score, and satisfaction score. A two‐sided P< 0.05 was considered to be statistically signifi-cant. Data analyses were performed with the softwareSPSS version 22.0 (IBM, Armonk, NY).

RESULTS

Overall, 20 subjects (13 males and 7 females, ages21–39 years, median age 28 years) with Fitzpatrick skintypes III–V were enrolled, and all of them completed thestudy. Most subjects have a mix of several types of scarsand were categorized into three types: rolling‐predomi-nant, boxcar‐predominant, or icepick‐predominant scars(Table 1).

Efficacy Evaluated by Dermatologists

Of the 40 image sets (20 subjects evaluated by twodermatologists), blinded reviewers correctly identified 33(82.5%) baseline images (Table 2). The reviewers rated amedian improvement score of 3 (range −7 to 8) for allsubjects. After averaging scores from the two reviewers,17 of 20 (85%) subjects showed some level of improvementand 9 (45%) subjects had an improvement score of at least3 (≥30%). For the 15 subjects whose baseline image wascorrectly identified by both reviewers, the median im-provement score was 4.5 (range 3–8). Subjects withrolling‐predominant scars responded better than subjectswith boxcar‐predominant and icepick‐predominant scars,with a median (mean [range]) improvement score of 4.5(4.08 [−2 to 8]), 4 (2.39 [−7 to 8]), and 2 (0.1 [−6 to 3]) forrolling‐predominant, boxcar‐predominant, and icepick‐predominant groups, respectively (Fig. 2). The dermatol-ogist‐rated improvement scores were not significantlyassociated with age, sex, or type of skin (Fig. 1b–c).

Efficacy Evaluated by Subjects

The subject rated median improvement score was 6.5 at1 month after the final treatment session. Furtherimprovement was reported at 3 months with a medianscore of 8 on global aesthetic improvement (P= 0.004).Subjects reported high satisfaction rates with the treat-ment results. Overall, 55% and 25% of subjects weresatisfied and very satisfied with their results at the 1‐month follow‐up, respectively. Subjects maintained satis-faction at the 3‐month follow‐up, with 55% and 40% beingsatisfied and very satisfied with the treatment outcome,respectively. There was a statistically significant correla-tion between subject‐rated improvement score and satis-faction score (Spearman’s rank ρ= 0.653, P= 0.002).FASQoL questionnaires showed significant improvementin the quality of life after laser treatment (median [range]:21 [4–40] before treatment vs. 10 [0–24] after treatment,P< 0.001).

PICOSECOND LASER FOR ACNE SCARS 3

Safety

Subjects reported a median pain score of 6 (range 2–9).Immediate post‐treatment responses were mild‐to‐mod-erate erythema, edema, exfoliation, petechiae, and blis-tering. All post‐treatment responses resolved within 10days with edema clearing a few hours after treatment,and erythema, exfoliation, and petechiae typically clear-ing a few days after treatment. The downtime rangedfrom 1 to 10 days, with a median of 4 days. Subjectsreported no dyspigmentation, oozing, or crusting at 1week, 1 month, and 3 months post‐treatment. No severeadverse events were observed during the study.

Histological Findings

Immediate post‐treatment histology revealed epidermalablation and well defined, intra‐epidermal vacuoles(Fig. 1d–g). Degenerating necrotic keratinocytes wereseen around the vacuoles.

DISCUSSION

This prospective study demonstrates that the high‐energy 1,064 nm picosecond laser with MLA is a safe andeffective treatment modality for acne scars in Asians. Asevaluated by two blinded dermatologists, the improve-ment was observed in 85% of the patients with a medianimprovement score of 3 after three treatment sessions.Subjects’ satisfaction was high with 19 of 20 subjectsbeing satisfied or very satisfied with their aestheticresults. A significant improvement in subjects’ quality oflife was also observed. There was no dyspigmentation,prolonged erythema, edema, acneiform eruption, miliaformation, hypertrophic scar, and delayed wound healingafter the treatment.

With the MLA, the high energy fluence deliversenergy to only 5% of the treated area in a single pass.Theoretically, the efficacy can be enhanced by increas-ing the passes or treatment sessions. In our study,1,200–1,600 laser pulses seemed inadequate for a full‐face treatment compared with other studies usingdifferent picosecond laser devices [18,19]. In the studyby Haimovic et al., who used a 755 nm Alexandritepicosecond laser (PicoSure®; Cynosure Inc., Westford,MA), 3,000–7,000 pulses were delivered in 2–4 passesfor the whole face in 56 patients with darker skin types[16]. However, regarding the larger spot size of 8 mmround and the higher fluence of 0.7–1.0 J/cm2 of thedevice we used, the smaller number of laser pulses inour study was reasonable. Besides this, perhaps due tothe larger numbers of laser pulses given in theHaimovic et al. study, six subjects developed postin-flammatory hyperpigmentation (PIH), which was notobserved in our study. Dierickx suggested that in-creased treatment pulses did not offer additionalbenefits for acne scars [18]. In contrast, Huang et al.showed that session number is positively associatedwith clinical improvement [19]. Therefore, furtherstudies are needed to determine the appropriate laserpulses and treatment sessions in the treatment of acnescars.

While grading scales exist for acne scarring, no consensushas been reached on the scar assessment tool to be selectedfor a given condition [20]. Therefore, it is difficult to comparethe results of different studies. The efficacy of laser treatmentwas assessed based on a 10‐point improvement scale in ourstudy, while a 4‐point scale or a 5‐point scale was used inother studies [15,19]. Compared with our study’s medianimprovement score of 3 on a 10‐point scale, the study byBernstein et al. demonstrated a mean improvement score of1.4 (range 4–6; 95% CI: 0.85–1.9) at 3 months after 4 monthlytreatments with a 1,064 and 532nm picosecond‐domain laser(PicoWay®; Syneron‐Candela Inc., Wayland, MA). The system

TABLE 1. Baseline characteristics of the subjects (n=20)

Age, y, median (range) 28 (21–39)Sex, n (%)Female 7 (35)Male 13 (65)

Fitzpatrick skin type, n (%)II 4 (20)III 12 (60)IV 4 (20)

Predominant scar type, n (%)Rolling 6 (30)Boxcar 9 (45)Icepick 5 (25)

TABLE 2. Efficacy and safety assessed by various para-meters (n=20)

P value

Efficacy evaluated by blindeddermatologists

Global improvement scale,median (range)

0.671

Reviewer 1 3.5 (−7 to 8)Reviewer 2 3 (−7 to 8)

Efficacy evaluated by subjectsGlobal improvement scale,median (range)

0.004

1‐month 6.5 (3–9)3‐month 8 (5–9)

Satisfaction score, median(range)

0.035

1‐month post final treatment 1 (−1 to 2)3‐month post final treatment 1 (0–2)

FASQoL, median (range) <0.001Before treatment 21 (4–40)After treatment 10 (0–24)

SafetyPain rating scale, median (range) 0.203Session 1 6 (2–9)Session 2 6 (2–8)Session 3 6 (2–9)

Abbreviation: FASQoL, Facial Acne Scar Quality of Life.

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used in the Bernstein et al. [21] study also utilized afractionated handpiece, which delivered an energy level of 1.3to 2.9mJ per microbeam. The energy level used in our studyis at least three times higher, and the treatment outcome isbetter without PIH being observed.Previous studies of fractional picosecond‐domain

devices demonstrated the dermal remodeling effect ofthe LIOB induced by the laser [22,23]. Our studyrevealed the optical breakdown and epidermal ablationproduced by the 1,064 nm picosecond‐domain laser. Tothe best of our knowledge, there is only one studyreporting microscopic ablation of the epidermis afterirradiation [24]. This is most likely due to the fluenceused for treatment. The energy per microbeam used inour study was 5.3–9.1 J per microbeam, while otherswere 1.3–2.9 J per microbeam [21]. Using the frac-tional picosecond Alexandrite laser, Brauer et al. [15]showed that the intra‐epidermal vacuoles were asso-ciated with increased dermal collagen, elastic tissue,and mucin. In the study by Guida et al. [25], who usedthe same 1,064 nm picosecond laser as ours, reflec-tance confocal microscopy revealed reticulated col-lagen fibers arranged in a net, suggesting increasedcollagen remodeling after laser treatment. However,further studies are necessary to elucidate the mechan-

isms underlying the clinical improvement in acne scarsfrom the treatment.

Asians have high melanocytic activity; therefore, theyhave a substantial risk of PIH after ablative lasers, suchas erbium:yttrium–aluminum–garnet or carbon dioxide(CO2) lasers [26–29]. Although the ablative, non‐fractio-nated CO2 laser is highly efficacious for the treatment ofacne scars, it might produce prolonged dyspigmentationand longer downtime. Fractionated CO2 lasers greatlyreduce the downtime but compromise the efficacy.Although fractionated, non‐ablative lasers have beenproved to be much safer than the CO2 laser, their efficacyin treating acne scars is suboptimal [30]. In our study, thelonger downtime and increase in pain during theprocedure might be associated with the epidermal abla-tion produced by the high fluence level. However, this1,064 nm picosecond‐domain laser achieved significantimprovement in acne scars with a low PIH risk, suggest-ing potential advantages of this device over earlierablative and non‐ablative fractionated lasers for treatingacne scars in darker skin types.

The low incidence of PIH in our study may be explainedby the MLA technology of this device. The MLA handpiecedelivers the laser in an array of narrow, focused high‐precision microbeams to create the thermal/plasma effecton both the epidermis and dermis. When the laser is

Fig. 2. A 36‐year‐old male with rolling‐predominant scars at baseline (a) and after 3 months offinal treatment (b). A 28‐year‐old male with icepick‐predominant scars at baseline (c) and after 3months of final treatment (d).

PICOSECOND LASER FOR ACNE SCARS 5

delivered at high fluence, plasma formation occurs beforephotons reach the dermis [31]. The multi‐photon ioniza-tion produces an electron avalanche, thereby leading to anepidermal breakdown. The surrounding tissue has limitedcollateral damage in the picosecond domain to ensurerapid healing and minimum side effect, explaining the lowincidence of PIH [22,32].The limitations of this study include relatively small

sample size, efficacy evaluation based on two‐dimensionalphotography, a follow‐up period of only 3 months, and lackof a comparative group. The use of two‐dimensionalimaging would probably not capture subtle changes inacne scars. Thus, this might explain the discrepancybetween the assessment of dermatologists and subjects’self‐assessment. Because scar tissue remodels over manymonths, further improvement could occur over a longerfollow‐up period. Finally, despite numerous tools availableto assess the severity of acne scars, the lack of consensusconcerning acne scar evaluation makes it difficult tocompare our results with those from other studies [33].This is the first report investigating the efficacy and

safety of the versatile picosecond laser with MLA in thetreatment of acne scars in Asians. In conclusion, the1,064 nm picosecond‐domain laser with a high‐energysetting is a safe and effective treatment modality for facialacne scars in Asians. The positive clinical outcomes and thesafety profile suggest that the 1,064 nm picosecond‐domainlaser is a promising therapeutic option for facial acne scars.

ACKNOWLEDGMENTS

This study was funded by the Ministry of Science andTechnology, R.O.C. under Grant (MOST 107–2314‐B‐075‐032‐MY3‐1).

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