management of acne scarring, part i · proper acne scar classification, laser scar revision...

Management of Acne Scarring, Part IA Comparative Review of Laser Surgical Approaches

Joseph F. Sobanko1 and Tina S. Alster2

1 Department of Dermatology, University of Pennsylvania, Philadelphia, PA, USA

2 Washington Institute of Dermatologic Laser Surgery, Washington, DC, USA

Contents

Abstract. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 319

1. Pathogenesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 320

2. Scar Classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 320

3. Acne Scar Treatment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 320

4. History of Laser Scar Revision . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 321

5. Hypertrophic Acne Scars . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 321

6. Atrophic Acne Scars . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 322

6.1 Laser Scar Revision of Atrophic Acne Scars . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 322

6.1.1 Ablative Resurfacing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 322

6.1.2 Nonablative Resurfacing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 324

6.1.3 Fractional Resurfacing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 324

7. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 327

Abstract Acne scarring is the result of a deviation in the orderly pattern of healing and can have profound

psychosocial implications for patients. While the most effective means of addressing acne scarring is to

prevent its formation through good acne control, there are a number of therapeutic interventions that

improve the appearance of acne scars. Many of these procedural modalities have flaws and are limited by

operator skill and experience. Laser scar revision, on the other hand, is a precise, well tolerated procedure

with clinically demonstrable efficacy and minimal adverse effects that may be used alone or in combination

with other scar treatments. The last 20 years has seen a dramatic evolution in laser treatment of acne scars,

spanning ablative and nonablative technologies, to the current popularity of fractional laser scar revision.

Determining which laser system to use depends upon the type and severity of acne scarring, the amount of

recovery a patient can tolerate, and the ultimate goals and expectations of each patient. The importance of

proper acne scar classification, laser scar revision techniques, and the evidence that addresses each laser

system is reviewed in this article.

Acne is believed to affect 45 million people in the US,

the overwhelming majority of whom are adolescents and

young adults.[1] The financial burden of acne in the US is

staggering, estimated at $US1 billion (March 2001) when loss

of productivity and unemployment are included in calcu-

lations.[1] Scarring is a common complication of acne, with

some degree of scarring observed in 95% of acne patients in

one clinical evaluation.[2] Other studies have reported much

lower incidences of scarring in acne patients, ranging from

0.17% to 14%.[3-5] Estimates of acne scarring are often in-

accurate because data are based on isolated pieces of infor-

mation such as medication purchases, hospital records, or

REVIEW ARTICLEAm J Clin Dermatol 2012; 13 (5): 319-330

1175-0561/12/0005-0319/$49.95/0

Adis ª 2012 Springer International Publishing AG. All rights reserved.

compensation claims rather than examining a full cross-

population sample.[6,7]

Unfortunately, the psychosocial impact of acne scarring can

be profound.[8] Scars that result from acne translate into

physical disfigurement and can place limitations on self-esteem,

social interactions, and daily activities. The ability to acquire

employment in adulthood may be limited in those with acne

scarring.[9] While it appears that the severity of one’s acne is

directly proportional to the severity of the acne scarring,[2] it is

important to note that levels of psychosocial distressmay not be

accurately predicted by one’s degree of disfigurement.[10] Thus,

it must be emphasized that the most effective means of mini-

mizing or preventing acne scarring and the subsequent psy-

chosocial difficulties that accompany it is to treat acne early and

effectively.[11]

1. Pathogenesis

A number of factors contribute to the pathogenesis of acne:

intense perifollicular inflammation, proliferation of Propioni-

bacterium acnes, increased sebum production, and follicular

hyperkeratinization appear to be the main etiologic fac-

tors.[12,13] A cascade of pro-inflammatory cytokines is stimu-

lated, leading to follicular rupture and perifollicular abscess

formation. This subsequently leads to a series of wound healing

events that may deviate from the orderly pattern of healing

whereby an imbalance of matrix degradation and collagen bio-

synthesis occurs.[14,15]

It has been demonstrated that acne patients prone to scar-

ring have a particular cellular infiltrate milieu different than

those patients who do not scar. Additionally, a prolonged in-

flammatory response at the follicle is noted in those patients

prone to scarring.[16] Throughout this process, an overzealous

healing response can create a raised nodule of fibrotic tissue,

whereas ‘pitted’ and atrophic scars may result from inadequate

replacement of deleted collagen fibers. Although vascular and

pigment alterations associated with wound healing are typically

transient, the textural changes caused by collagen disruption

are often permanent. Histologically, whatmakes scars unique is

the relative absence of skin appendages and elastic fibers –

constituents of normal skin that may account for the loss of

flexibility seen in scar tissue.[17]

2. Scar Classification

For the purposes of practicality and ease in treatment se-

lection, acne scars should be categorized as either ‘hyper-

trophic’ or ‘atrophic’. Atrophic scars may be further subdivided

into icepick, rolling, and boxcar types. Other descriptors such

as ‘pitted’ and ‘crateriform’ have been used in the past to

identify acne scars. Unfortunately, these terms are vague and

subjective. In order to unify the terminology and enable com-

parisons of treatments across different studies, clinicians

should adhere to the recommended nomenclature.

Hypertrophic scars are erythematous, raised, firm nodular

lesions. The growth of hypertrophic scars is limited to the sites

of original tissue injury, unlike keloids that proliferate beyond

the boundaries of the initial wounds and often continue to grow

without regression. Keloids present as deep reddish-purple

papules and nodules, often on the anterior chest, shoulders, and

upper back. They are more common in darker-skinned persons

and, like hypertrophic scars, may be pruritic, dysesthetic, and

cosmetically disfiguring. While the histology of hypertrophic

scars is indistinguishable from that of other scarring processes,

keloidal histology may be recognized by thickened bundles of

hyalinized acellular collagen haphazardly arranged in whorls

and nodules with an increased amount of hyaluronidase.[18]

Atrophic scars, on the other hand, are dermal depressions

that result from the aforementioned acute inflammatory pro-

cesses. The inflammation associated with atrophic scars leads

to collagen destruction with dermal atrophy. Atrophic scars are

initially erythematous and become increasingly hypopigmented

and fibrotic over time. In 2001, Jacob et al.[19] unified the vague

terminology previously used to describe atrophic acne scars

by proposing a classification based on the width, depth, and

3-dimensional architecture of acne scars. The authors suggested

classes included icepick, rolling, and boxcar scars.[19] Icepick

scars are narrow, v-shaped epithelial tracts that extend into the

deep dermis or subcutaneous tissue. Rolling scars are wide and

undulating, due to their tethering from the dermis below. Fi-

nally, boxcar scars are sharply delineated epithelial tracts that

extend into the dermis but, unlike icepick scars, do not taper at

the base. Use of this classification system allows for treatments

to be tailored to the specific type of scarring.

3. Acne Scar Treatment

Patients frequently seek treatment for improvement of their

acne scars. It is imperative for physicians to recognize that

physical improvement of scars can translate into improved

psychosocial well-being and behavior of patients.[10,20] Many

treatments have been attempted in order to improve acne

scarring. Chemical peels, surgical excision, subcision, punch

grafting, dermabrasion, and tissue augmentation with a variety

of fillers have been used to ameliorate acne scars with varying

degrees of success.[18] The clinical utility of these treatments has

320 Sobanko & Alster

Adis ª 2012 Springer International Publishing AG. All rights reserved. Am J Clin Dermatol 2012; 13 (5)

been limited by incomplete scar removal, poor intraoperative

visualization, transmission of infectious debris, scar worsening,

tissue fibrosis, and permanent pigmentary alteration.[18] Ad-

vances in laser technology have led researchers to study their

potential use as a treatment for this therapeutically difficult

condition.[18,21,22] Laser scar revision is a well tolerated proce-

dure with clinically demonstrable efficacy and minimal adverse

effects and may be used in combination with the afore-

mentioned scar treatments.

4. History of Laser Scar Revision

Although laser surgery is more than 5 decades old, the

field was revolutionized in 1983 when Anderson and Parrish[23]

elucidated the principles of selective photothermolysis. This

basic theory of laser-tissue interaction explains how selective

tissue destruction is possible. In order to effect precise thermal

destruction of target tissue without unwanted conduction of

heat to surrounding structures, the proper laser wavelength

must be selected for preferential absorption by the intended

tissue chromophore. Furthermore, the pulse duration of laser

emissionmust be shorter than the thermal relaxation time of the

target – thermal relaxation time (TR) being defined as the

amount of time necessary for the targeted structure to cool to

one-half of its peak temperature immediately after laser irra-

diation. The delivered fluence (energy density) must also be

sufficiently high to cause the desired degree of thermal injury to

the skin. Thus, the laser wavelength, pulse duration, and flu-

ence each must be carefully chosen to achieve maximal target

ablation while minimizing surrounding tissue damage.

Laser systems are versatile tools that allow for a broad range

of cutaneous maladies to be treated. Scar improvement with a

pulsed dye laser was first reported by Alster and colleagues[24]

in 1993 and, over the subsequent 2 decades, laser scar revision

progressed tremendously due to advances in technology. Laser

treatment of acne scars is optimized by proper scar catego-

rization. Several qualities of the scar, including size, color,

texture, and prior treatments influence choice of laser wave-

length and treatment parameters.

5. Hypertrophic Acne Scars

Until 15 years ago, the treatment of acne scars was limited to

procedures that included dermabrasion, chemical peels, and

primitive ablative resurfacing lasers such as the argon and

continuous-wave carbon dioxide (CO2) lasers. Prolonged ery-

thema, scarring, and recurrence were common with these mo-

dalities.[25-27] The first report of a nonablative laser being

successful for hypertrophic, erythematous facial acne scars

was published in 1996.[28] In this split-face, controlled, blinded-

observer study with a 585 nm pulsed dye laser (PDL), 22

subjects underwent laser treatment to facial halves with contra-

lateral facial halves serving as untreated controls. An average

fluence of 6.5 J/cm2 (0.45ms pulse, 7mm spot) was used to treat

scars over one or two sessions. Erythema was measured with

reflectance spectroscopy, skin texture analyses were obtained

via silicone rubber impressions, and clinical assessments were

made by two independent masked practitioners. The average

clinical improvement 6 weeks after one session was 67.5% and

the degree of scar erythema after laser irradiation was not sig-

nificantly different from readings obtained from normal skin

(p < 0.01).

There is no consensus on the precise mechanismwhereby the

PDL exerts its effect on scars. The PDL has been demonstrated

to reduce transforming growth factor-b expression, fibroblast

proliferation, and collagen type III deposition.[29] Other plau-

sible explanations include selective photothermolysis of vas-

culature,[30] released mast cell constituents (such as histamine

and interleukins) that could affect collagen metabolism,[31] and

the heating of collagen fibers and breaking of disulfide bonds

with subsequent collagen realignment.[32] In fact, the PDL has

been successful in improving the depth of moderately atrophic

facial acne scars, likely due to stimulation of collagen remod-

eling.[33] As a consequence of this research, the laser of choice in

treating hypertrophic, erythematous acne scars and keloids is

the vascular-specific 585 nm PDL (figure 1).[34-36]

The use of concomitant intralesional corticosteroids or

fluorouracil has been shown to provide additional benefit in

proliferative scars.[37,38] Intralesional injections of corticoste-

roids (20mg/mL triamcinolone) are more easily delivered im-

mediately after (rather than before) PDL irradiation because

the laser-irradiated scar becomes edematous (making needle

penetration easier). An additional consideration is that when

corticosteroid injection is performed before laser irradiation,

the skin blanches, rendering the skin a potentially less amenable

target for vascular-specific irradiation.

The most common adverse effect of treatment with the PDL

is postoperative purpura, which often persists for several days.

Pulse durations shorter than 6ms are almost certain to bruise

the skin. Edema of treated skin may also occur, but usually

subsides within 48 hours. A topical healing ointment under a

nonstick bandage can be applied for the first few postopera-

tive days to protect the skin. Treated areas should be gently

cleansed daily with water and mild soap. Strict sun avoidance

and photoprotection should be advocated between treat-

ment sessions in order to reduce the risk of pigment alteration.

Management of Acne Scarring, Part I 321


Hyperpigmentation has been reported with varying frequencies

(1–24%).[38,39] If skin darkening occurs, further laser treatment

should be suspended until resolution of the dyspigmentation

has occurred in order to reduce the risk of cutaneous melanin

interference with laser energy penetration. Topical bleaching

agents (such as hydroquinone or kojic acid) may be applied to

hasten pigment resolution.

6. Atrophic Acne Scars

Most acne scars tend not to be erythematous and elevated.

More often, patients present with atrophic scars that may or

may not be erythematous. Some authors[15] state that the ratio

of atrophic to hypertrophic acne scars is 3 : 1. It is helpful to

distinguish atrophic scars as icepick, rolling, and boxcar sub-

types since each subtype may respond differently to various

surgical interventions.[19] For example, icepick scars appear to

be most amenable to correction by punch excision.[19] While

there are other surgical interventions for atrophic acne scars

(including chemical peels, subcision, soft tissue fillers, der-

mabrasion), their operator-dependent efficacies and adverse-

effect profiles, as well as temporary clinical effects (in the case of

filler injections), limit their usefulness and widespread accept-

ance for the long term. Laser scar revision is a precise, well

tolerated procedure with clinically demonstrable efficacy and

minimal adverse effects that may be used in combination with

the aforementioned scar treatments. It is for this reason that all

patients with boxcar and rolling acne scars are excellent can-

didates for laser resurfacing.[15] The remainder of this section

will address the use of lasers for atrophic scars. Because prior

studies have not been rigorous with distinguishing the various

types of acne scars, boxcar and rolling acne scars will be con-

sidered together.

6.1 Laser Scar Revision of Atrophic Acne Scars

6.1.1 Ablative Resurfacing

There has been a dramatic evolution of laser skin resurfacing

over the past 5 decades. CO2 lasers were first introduced in the

1960s, but had limited utility because they could not remove

fine layers of tissue in a controlled and predictable manner.

Significant thermal damage, scarring, and pigmentary changes

were often observed.With the subsequent development of high-

energy, pulsed lasers, and their US FDA approval in 1996, it

became possible to safely apply higher energy densities with

exposure times that were shorter than the thermal relaxation

time of water-containing tissue. These features lowered the risk

of thermal injury to surrounding non-targeted structures and

allowed laser vaporization to become accepted as the treatment

of choice for atrophic facial acne scars.[40] Subsequent ablative

lasers such as the short-pulsed erbium:yttrium-aluminum-

garnet (Er:YAG) followed, which produced fewer adverse

events and less postoperative recovery, while maintaining

clinical benefit.[41,42]

Far infrared CO2 (10 600 nm) and Er:YAG (2940 nm) lasers

work to selectively heat and vaporize superficial skin by emitting

energy that is absorbed by intracellular tissue water. Cutaneous

laser resurfacing produces an additional skin tightening benefit

through controlled heating of dermal collagen. The depth of

ablation correlates directly with the number of passes performed

and is usually confined to the epidermis and upper papillary

a

b

Fig. 1. Erythematous acne and scars before (a) and after (b) two pulsed dye

laser treatments.



dermis; however, stacking of laser pulses by treating an area

with multiple passes in rapid succession or by using a high

overlap setting on a scanning device can lead to excessive

thermal injury with subsequent increased risk of scarring.[43] An

ablative plateau is reached with less effective tissue ablation and

accumulation of thermal injury due to reduced tissue water

content after initial desiccation. The avoidance of pulse stack-

ing and incomplete removal of partially desiccated tissue is

paramount to prevention of excessive thermal accumulation

with any laser system. The photothermal effect of ablative la-

sers on the skin account for shrinkage of collagen, as well as

neocollagenesis and collagen remodeling leading to marked

improvement of skin textural irregularities, skin tightening, and

lifting.[44,45]

Laser treatment of atrophic scars is aimed at reducing the

depth of the scar borders and stimulating neocollagenesis to fill

in the depressions. Although spot (or local) vaporization of

isolated scars is a viable treatment option, extended treatment

(at least an entire cosmetic unit) is recommended for more

widely distributed defects to avoid obvious lines of demarcation

between treated and untreated sites. In addition, treatment of

a larger surface area increases the overall collagen tightening

effect, thereby improving clinical response by making scars

appear shallower.

While several studies reported the safety and efficacy of

treating atrophic facial scars with a high-energy pulsed CO2

laser,[46-48] it was not until 1999 that the prolonged clinical and

histologic effects of this treatment were documented.[49] In this

prospective series of 60 patients, continued clinical improve-

ment was observed for 18 months after CO2 resurfacing. Pro-

gressive neocollagenesis and dermal remodeling were also

observed in histologic tissue specimens during this same time

period. Based on this observation, the authors proposed that

longer postoperative intervals (12–18 months) be advocated

before prescribing additional laser treatments, thereby per-

mitting optimal tissue recovery and providing an opportunity

for collagen remodeling.

The 2940 nm Er:YAG laser is 12–18 times more efficiently

absorbed by water-containing tissue than is the 10 600 nm CO2

laser. The pulse duration (averaging 250 ms) is also much

shorter than that of the CO2 laser (1ms), resulting in decreased

thermal diffusion, less effective hemostasis, and increased in-

traoperative bleeding, which can hamper deeper dermal treat-

ments.[40,50-52] Because of limited thermal skin injury, the

amount of collagen contraction is also reduced with Er:YAG

treatment compared with that observed with CO2 laser irradi-

ation.[44] To address the limitations of short-pulsed Er:YAG

lasers, modulated Er:YAG and combination Er:YAG-CO2

laser systems that emit a combination of short ablative pulses

and long coagulative pulses were developed to improve hemo-

stasis and increase collagen shrinkage and remodeling.[41] The

collagen contraction induced bymodulated Er:YAG lasers was

found to be similar in degree to that of CO2 lasers; however,

they required a longer period of time for this to be achieved.[44]

In a prospective study of 25 consecutive atrophic acne

patients treated with a modulated (dual-mode) Er:YAG laser,

the average clinical grading score was good to excellent.[41] Simi-

lar results were demonstrated with the long-pulsed Er:YAG

laser in a prospective study of acne scar patients, where 93%of patients were deemed to have a ‘good’ or ‘excellent’ res-

ponse.[53] A larger study that included 158 patients with various

types of atrophic acne scars assessed the results of treatment by

three different Er:YAG laser systems.[54] Improvement was

seen in shallow boxcar and icepick scars with all three Er:YAG

lasers; however, rolling and deep boxcar scars were best treated

with an Er:YAG laser with a long pulse duration in order to

maximize the thermal effect on treated tissue.

Ablative laser scar revision is typically performed on an out-

patient basis and requires a thoughtful approach by both doctor

and patient, including thorough preoperative counseling re-

lated to the postoperative recovery period. Absolute contra-

indications to ablative laser skin resurfacing include an active

cutaneous bacterial, viral, or fungal infection.[55,56] Patients

with an inflammatory skin condition (e.g. psoriasis, eczema)

involving the skin areas to be treated should not be treated until

the condition clears. Isotretinoin use within the preceding

6-month period or history of keloids are also considered con-

traindications to ablative laser treatment because of the un-

predictable tissue healing response and greater risk for scarring.[57]

All persons in the treatment room must wear protective

eyewear. If patients are wearing protective contact lens shields,

sandblasted metal ones must be chosen since plastic shields do

not meet safety standards for ocular protection during peri-

ocular laser irradiation. The concave surface of the shields

should be liberally lubricated with an ophthalmic ointment and

care must be taken while inserting and removing the shields in

order to prevent corneal abrasions.

Immediately after laser ablation, the vaporized skin appears

erythematous and edematous, with copious serous discharge

and generalized worsening of the skin’s appearance over the

first few days. It is imperative that patients bemonitored closely

for appropriate healing responses and potential complications,

such as dermatitis or infection, during the 7- to 10-day re-

epithelialization process.[55,56,58] Full-face procedures or large

treatment areas often necessitate the use of prophylactic anti-

bacterials and/or antiviral medications to reduce the risk of



infection.[59-61] The use of topical antibacterials is avoided due

to the potential development of contact dermatitis.[62] Appli-

cation of topical ointments, semiocclusive dressings, and/orcooling masks promote healing and reduce swelling.

Postoperative erythema typically lasts several weeks after

ablative laser treatment due to tissue necrosis. Hyperpigmenta-

tion is transient and generally appears 3–4 weeks after treat-

ment. Its resolution can be hastened with the use of topical

bleaching agents.[55,56,63] Although hyperpigmentation is rela-

tively common (particularly in patients with darker skin tones),

hypopigmentation is rare.[58] The most severe complications of

ablative skin resurfacing include hypertrophic scarring and

ectropion formation, both related to overly aggressive laser

techniques and/or undiagnosed/untreated suprainfections.[55,56,63]

Hypertrophic burn scars can be effectively treated with the

PDL,[32] whereas ectropion typically requires cold steel surgical

revision. Retreatment after ablative laser skin resurfacing

should be postponed for at least 1 year to accurately gauge

clinical improvement and permit full tissue recovery.[49]

6.1.2 Nonablative Resurfacing

As a consequence of the adverse effects and prolonged

postoperative recovery associatedwith ablative laser treatment,

nonablative lasers were subsequently developed to provide a

noninvasive option for atrophic scar revision.[64] The most

popular and widely used of these nonablative systems include

the 1320 nm Nd:YAG, 1450 nm diode, and 1064 nm Nd:YAG

lasers. These devices deliver concomitant epidermal surface

cooling with deeply penetrating infrared wavelengths that tar-

get tissue water and stimulate collagen production through

dermal heating without disruption of the epidermis.[65,66] Be-

cause there is no disruption of the epidermal barrier, post-

treatment recovery time is minimal as is the likelihood of ad-

verse events.

A number of studies have demonstrated mild to moderate

improvement in atrophic acne scars using these nonablative

lasers. Six months after three sessions with a 1320 nmNd:YAG

laser, 12 subjects with atrophic and mixed acne scars showed

significant improvement in scarring as reported by both phy-

sicians and patients without evidence of reported complica-

tions.[67] Other larger prospective studies with the 1320 nm

Nd:YAG laser have shown similar, modest efficacy without

notable adverse events.[68,69]

When the 1450 nm diode laser was used in a prospective

study in 57 Asian patients, modest improvements (15–20%improvement) were seen in atrophic acne scars after 4–6 treat-

ments; however, 40% of patients reported no clinical im-

provement whatsoever.[70] In a split-face, prospective study of

20 subjects comparing the effects of the 1450 nm diode laser

with a 1320 nmNd:YAG laser, both lasers demonstrated amild

improvement of atrophic scars after 3 monthly sessions. The

1450 nm diode laser did show a greater clinical effect and nei-

ther laser produced any adverse textural changes.[71]

Mild to moderate clinical improvement in atrophic acne

scars was also demonstrated with 1064 nm Nd:YAG laser

treatment in 12 subjects who received 5 monthly sessions.[72]

Additionally, histologic examination of treated scars 1 month

after the final laser session revealed statistically significant in-

creases in collagen.[72] Comparison of the 1064 nm Nd:YAG

and the 585 nm PDL demonstrated that both lasers were ef-

fective in the treatment of superficial boxcar and rolling scars

but less effective in the treatment of deep boxcar, deep rolling,

and ice-pick scars.[73] Skin biopsies also revealed significant

increases in collagen production and deposition after treatment

with either laser.[73] In a similar study comparing a combination

585/1064 nm laser with a 1064 nm Nd:YAG laser, acne scars

showed mild to moderate improvements with both treatments.

This study also suggested that deep boxcar acne scars may

potentially respond better to the combination 585/1064 nmsystem, although this finding was not statistically significant.[74]

While nonablative lasers do not demonstrate the ability to

produce the dramatic improvement in atrophic acne scars as do

ablative systems, studies have determined that they are safe and

modestly effective. A series of 3–5 treatments are typically

performed on a monthly basis with optimal clinical efficacy

observed several (3–6) months after the final laser session. At

best, sustained clinical improvement of scars by 40–50% can be

expected. The low adverse-effect profile of these nonablative

systems (limited to local erythema and edema and, rarely, ve-

siculation or herpes simplex reactivation) compensates for their

reduced clinical efficacy (relative to ablative lasers).[64,66]

6.1.3 Fractional Resurfacing

Due to a need formore noticeable clinical improvement than

the aforementioned nonablative systems could deliver, but with

their favorable safety and recovery profiles, fractional lasers

were developed. In its relatively short history, fractional laser

technology has progressed rapidly, with over 30 commercially

available fractional systems on the market. These laser systems

may best be classified into two categories: nonablative frac-

tional lasers (NAFL) and ablative fractional lasers (AFL).[75,76]

The initial fractional laser (Fraxel�, Reliant Technologies,

Mountain View, CA, USA) involved the use of a mid-infrared

(1550 nm) wavelength erbium-doped fiber laser to createmicro-

scopic noncontiguous columns of thermal injury in the dermis

(referred to as microscopic thermal zones orMTZs) surrounded



by zones of viable tissue. The spatially precise columns of

thermal injury produce localized epidermal necrosis and col-

lagen denaturation at 125 or 250MTZ/cm2.[77,78] Because the

tissue surrounding each MTZ remains intact, residual epi-

dermal and dermal cells contribute to rapid healing. Mainten-

ance of the stratum corneum ensures continued epidermal

barrier function.

Histologic evaluation of the MTZ demonstrates homoge-

nization of the dermal matrix and the presence of epidermal

necrotic debris (MEND), representing the extrusion of dam-

aged epidermal keratinocytes by viable keratinocytes at the

lateral margin of the MTZ.[78] The necrotic debris exfoliates

over the next several days, producing a bronzed appearance to

the skin. The wound healing response differs from that after

ablative laser techniques because the epidermal tissue that is

spared between thermal zones contains viable transient ampli-

fying cells capable of rapid re-epithelialization. Furthermore,

because the stratum corneum has low water content, it remains

intact immediately after treatment. Therefore, the coagulative

wound created by NAFL resurfacing is unique – not simply

that of an ablative laser used to make ‘holes’ in the skin. In

addition, NAFL resurfacing can provide an advantage over

purely nonablative laser treatments due to the gradual ex-

foliation of the epidermis with resultant improvement in su-

perficial dyspigmentation.[79] A series of NAFL treatments is

required to achieve optimal clinical improvement because only

a fraction of the skin is treated during a single session.

There are two main parameters that can be adjusted when

using the NAFL: the energy setting (mJ) and the treatment

density (treatment level). The energy setting varies the depth of

penetration, with higher settings penetrating deeper into the

dermis. Newer models of the NAFL allow for dermal pene-

tration ranging between 300 and 1400 mm. The treatment den-

sity may range from 5% to 48% coverage, with higher levels

resulting in greater thermal injury and subsequent collagen

remodeling.[80]

Significant clinical improvement has been shown when

nonablative fractional photothermolysis is applied to atrophic

facial acne scars of mild to moderate severity (figure 2).[81-87] In

a randomized study evaluating the effects of a NAFL on

moderately atrophic acne scars, ten patients underwent a split-

face protocol where facial halves received 3 monthly laser

treatments with a 1540 nm NAFL (Palomar Medical Tech-

nologies, Burlington, MA, USA) and the contralateral face

received no treatment.[88] Blinded evaluations before treatment

and at 4 and 12 weeks after the final session verified that scars

appeared more even and smooth than the contralateral non-

treated side and patients expressed satisfaction with the results.

It is standard practice that acne scar patients be treated

with the NAFL on a monthly basis with greater clinical im-

provement seen with successive treatments. Many studies

have demonstrated that clinical improvement of 50% or

more is observed in acne scarring after a series of three con-

secutive NAFL treatments.[81-83,85-87] It has been shown that

the use of higher energy settings and multiple laser passes

translate into improved clinical results, while use of increased

densities is more likely to result in increased incidence, sever-

ity, and duration of post-treatment erythema, edema, and

hyperpigmentation.[89,90]

Consensus guidelines on NAFL treatment parameters for

acne scars have been proposed for different skin phototypes.[80]

a

b

Fig. 2. Atrophic acne scars on the cheek before (a) and after (b) 3 monthly

nonablative fractionated laser treatments.



For lighter skin phototypes (I–III), the recommended settings

are 30–70mJ energy, treatment level of 7–11, and 8–12 passes.

For darker skin phototypes (IV–VI), energy settings of

30–70mJ are advocated with fewer passes and lower treatment

density in order to decrease the likelihood of postinflammatory

hyperpigmentation.[91] Clinical efficacy of lower energy settings

can be maintained by increasing the total number of treatment

sessions delivered.

In contrast, AFLs (fractionated CO2 and erbium lasers) not

only create similar columns of thermal coagulation through the

epidermis and dermis, they also vaporize the stratum cor-

neum.[92] Because of the absence of a protective cap overlying

the coagulated columnar regions, the immediate postoperative

appearance of treated areas is more similar to an ablative

treatment than that observed with NAFL. Unlike fully ablative

treatments, AFLs not only deliver sufficient energy to effect

immediate contraction, but intact islands of viable epidermis

remain post-treatment that facilitate rapid healing.[93,94] In-

tense erythema and serosanguinous drainage are evident for

2–3 days, followed by complete re-epithelialization and di-

minution of erythema by postoperative day 6 or 7.[95]

Chapas et al.[96] first demonstrated success with AFL re-

surfacing in moderate to severe acne scars. In this study, 13

subjects received 2 or 3 monthly treatments with a fractional

CO2 laser (Fraxel� re:pair laser prototype, Reliant Tech-

nologies, Inc.,Mountain View, CA,USA). Results were graded

on a quartile scale by subjects and investigators after each

treatment as well as 1 and 3 months after the final treatment.

Quartile grading scores correlating to at least 26–50% im-

provements in texture, atrophy, and overall improvement were

noted in all patients and topographic analysis revealed a mean

improvement of 66.8%. Numerous subsequent studies have

reported similar successwithAFLs for atrophic acne scars.[97-101]

Interestingly, when the AFL is used at a lower energy in tandem

with a nonablative laser (1064 nmNd:YAG), it appears that the

clinical efficacy and adverse events are even better than that of

an AFL used alone at a higher energy.[102]

Similar to NAFLs, clinical improvement of atrophic scar-

ring with AFLs results from collagen contraction and neo-

collagenesis (figure 3). One published study has compared the

effects of NAFL with AFL on atrophic scars.[103] In this ran-

domized, split-face, blinded response protocol, eight patients

had half of their face treated with a single-session NAFL and

the other half treated with a single-session AFL. Three months

after treatment, all eight patients exhibited equal or greater

clinical improvement scores with theAFL thanwith theNAFL.

Unfortunately, comparing these two laser types after a single

session is inherently flawed since a series of NAFL treatments is

generally needed to rival the effects of one AFL treatment.

Treatment of scars with AFL systems may prove to be more

effective than NAFL treatment given that AFL energy pene-

trates deep (1.5–1.6mm) into the dermis with a prolonged

wound remodeling response of several months’ duration.[104]

The effects of the AFL also appear to be prolonged, with one

case series demonstrating that patients maintain up to three-

quarters of their overall improvement at long-term (1–2 years

postoperative) follow-up.[100]

While the ideal patient for fractional laser skin resurfacing

has a fair complexion (skin phototypes I, II, or III), darker skin

tones (IV–VI) can also be treated. Wang and colleagues[105]

demonstrated mild to moderate improvement of moderate to

a

b

Fig. 3. Atrophic acne scars on the back before (a) and after (b) one ablative

fractionated laser treatment.



severe acne scars in type IV skin. Although the prospective

study was small (n = 5) and the follow-up short (2 months), the

authors encouragingly note that post-treatment dyspigmenta-

tion was not observed in any subjects, likely due to the con-

servative parameters selected. Adequate preoperative patient

evaluation and education are necessary in order to discern

unrealistic patient expectations, avoid pitfalls, and optimize

clinical outcomes. Prolonged postoperative recovery, pig-

mentary alteration, or unexpected scarring is much less likely to

occur with fractionated technology than fully ablative lasers,

but patients must nevertheless be forewarned. For patients

unable or unwilling to withstand the anticipated 3–7 days of

postoperative healing, a series of nonablative (fractionated or

infrared) laser procedures may be a more suitable choice.

The optimal settings will vary depending on the laser used

and the severity and type of scarring present. Higher energy

settings may result in improved clinical efficacy, but are also

associated with increased adverse events (pain, erythema,

postoperative dyspigmentation).[106,107] Patients who receive

NAFL treatment should use a mild cleanser and moisturizer

several times daily for the first few days after each treatment

session (or as long as bronzing/xerosis is apparent). Sun ex-

posure should be avoided during this time. Postoperative ery-

thema resolves spontaneously but its intensity and duration

may be reduced by immediate treatment with a 590 nm wave-

length light-emitting diode array.[108] On the other hand, those

who receive treatment with an AFL must undergo open or

closed wound care as previously described in section 6.1.1 for

the first several postoperative days. Thereafter, patients can

slowly resume the use of their regular skin-care products.

Fractional skin resurfacing is associated with a relatively low

complication rate.[106,107] Most untoward events of NAFL treat-

ment are mild and transient including erythema, periocular

edema, xerosis, and slight darkening of the skin (bronzing)

during desquamation of the microscopic epidermal necrotic

debris.[106] The most commonly encountered adverse events

reported are acneiform and herpetic eruptions in fewer than 2%of patients. Postinflammatory hyperpigmentation may also

occur, particularly in patients with darker skin phototypes.[109]

Intense erythema, serosanguinous drainage, and crusting are

typical for 5–7 days after AFL treatment (compared with

2–3 days with NAFL).[107] Caution must be advised with

treating skin in areas that are thin or devoid of pilosebaceous

units. Although rare, hypertrophic scarring of the neck, chest,

and periocular regions has been reported with AFLs,[110,111] so

overly aggressive treatment settings should be avoided in these

sensitive anatomic sites. To date, permanent pigmentary al-

teration has not been reported. Other exceedingly rare adverse

events, such as eruptive keratoacanthomas and recall phe-

nomenon, have also been reported.[112,113]

7. Conclusion

Acne scars are relatively common and lead patients to seek

treatment for cosmetic improvement. Currently, the many

medical scar treatments that are available often prove in-

adequate or inconvenient. It is precisely for these reasons that

laser therapy has been investigated for scar revision.

There are several laser systems available that permit success-

ful treatment of various types of scars. The 585 nm PDL re-

mains the workhorse for laser treatment of hypertrophic acne

scars. Atrophic scars may best be treated with ablative and

fractionally ablative and nonablative laser systems, depending

on specific patient circumstances. These lasers appear to re-

model the scar contouring via collagen contraction and neo-

collagenesis. AFLs may more be more effective than NAFLs

but longer postoperative downtime periods and a slightly higher

potential for adverse events must be tolerated. Nonablative

systems, although less clinically efficacious, may be used in

patients desiring a treatment with minimal to no postoperative

recovery. Laser scar revision is optimized when individual pa-

tient and scar characteristics are thoroughly evaluated to de-

termine the best course of treatment and, more importantly, to

determine whether the patient and physician share realistic

expectations and treatment goals.

Acknowledgments

No sources of fundingwere used to prepare this review. The authors have

no conflicts of interest that are directly relevant to the content of this review.

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of facial scars. Facial Plast Surg Clin N Am 2011; 19: 527-42

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the treatment of atrophic acne scarring in Asian patients: a pilot study.

J Cosmet Laser Ther 2010; 12: 61-4

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laser photothermolysis: experience with 961 treatments. Dermatol Surg

2008; 34: 301-7

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plications: a review. Dermatol Surg 2010; 36: 299-306

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ythemawith light-emitting diode photomodulation.Dermatol Surg 2009; 35:

813-5

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doped yttrium aluminum garnet fractionated laser for treatment of acne

scars in type IV to VI skin. Dermatol Surg 2010; 36: 602-9

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resurfacing: four cases. Lasers Surg Med 2009; 41: 179-84

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Correspondence: Dr Tina S. Alster, Washington Institute of Dermatologic

Laser Surgery, 1430 K Street, NW Suite 200, Washington, DC, 20005, USA.

E-mail: [email protected]



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