Combining correct laser device with type of acne scar boosts clearance

Joely Kaufman, M.D.

Jeremy Green, M.D.Acne scars are potentially socially debilitating lifelong reminders of the condition. Fortunately, modern laser therapy allows dermatologists to offer their patients hope for improvement. Prior to initiating laser therapy for acne scars it is important to consider the types of scars encountered. Laser is not a “one-size fits all” treatment - erythematous/hyperpigmented macular, hypertrophic, atrophic, ice pick, rolling or boxcar scars can each necessitate unique interventions.

Pulsed light approach

Pink-erythematous scars result from dilatation of dermal blood vessels. A tincture of time can be sufficient for some red scars to resolve, but to offer patients expeditious improvement a variety of devices are available, including intense pulsed light, pulsed dye laser (PDL, 585 nm–595 nm; Alster TS, McMeekin TO. J Am Acad Dermatol. 1996;35(1):79-87) and the potassium titanyl phosphate laser (KTP, 532 nm).

These long-pulsed devices take advantage of oxyhemoglobin’s avid absorption of light in the shorter wavelength visible spectrum to selectively target the dilated blood vessels while minimizing collateral heat spread. Treatments are safe in hair-bearing areas, though we recommend a close shave for men prior to treatment.

With the aforementioned devices the authors prefer using the shorter end of the available pulse durations. A South Korean group reported excellent results with both the PDL and the 1064 nm neodymium-yttrium-aluminum-garnet (Nd:YAG) for atrophic acne scars (Lee DH, Choi YS, Min SU, et al. J Am Acad Dermatol. 2009;60(5):801-807).

This split-face trial of 18 patients receiving four sessions with each laser revealed clinical scar improvement as well as histologic evidence of neocollagenesis. Hyperpigmented scars may be approached with the same devices (IPL, KTP or PDL) though quality-switched lasers (KTP, 694 nm ruby, 755 nm alexandrite, and Nd:YAG) with pulse durations in the nanosecond domain offer another option.

Revolutionizing treatment

Fractional lasers have revolutionized the treatment of all types of acne scars. In contrast to their confluent predecessors, these lasers divide or fractionate the laser beam to create tiny microthermal injury zones, sparing surrounding tissue and inducing collagen remodeling. This allows for treatment with less downtime and lower risk of side effects, including scarring.

Like their predecessor resurfacing devices, these fractional devices all use water as their chromophore. Nonablative fractional resurfacing utilizes mid-infrared light to induce microthermal treatment zones of coagulative necrosis without vaporizing the epidermis.

The primary advantage of these lasers versus ablative fractional resurfacing treatments is the reduced downtime and side effects, plus the ability to treat all skin types. As a consequence, however, a series of nonablative fractional resurfacing treatments is needed to achieve comparable results to a single ablative fractional resurfacing treatment.

Researchers have studied the 1,320 nm Nd:YAG, 1,450 nm diode, 1,540 nm and 1,550 nm erbium glass wavelengths. Geronemus et al first reported the use of nonablative fractional resurfacing for acne scars (Geronemus R. Lasers Surg Med. 2006;38(3):169-176). After five 1,550 nm laser treatments patients experienced 25-50 percent mean clinical improvement with no adverse events.

A recent evaluation of the 1,540 nm laser in 20 patients receiving four monthly treatments followed for three months found that 80 percent of patients noted improvement with 40 percent characterizing their scars “much improved,” (Isarria MJ, Cornejo P, Munoz EM, et al. J Drugs Dermatol. 2011;10(8):916-921).

Avoiding PIH

Of paramount concern in any acne scar laser treatment of dark skin types is postinflammatory pigment alteration. Chan and colleagues sought to elucidate the optimum safe parameters for nonablative fractional resurfacing (Chan HH, Manstein D, Yu CS, et al. Lasers Surg Med. 2007;39(5):381-385).

In a split-face study of 32 Asian women with skin types III and IV, researchers found that areas treated with higher density 1,550 nm laser had increased edema, erythema and hyperpigmentation, whereas the sides treated with lower density had no pigment changes. The group treated with low density and high fluence had the best clinical improvement and patient satisfaction scores.

Dr. Chan’s group reported similar experience with the 1,540 nm erbium laser in Asian skin, as patients receiving low density/high fluence treatment had less postinflammatory hyperpigmentation (PIH), though this difference did not achieve statistical significance (Chan HH, Manstein D, Yu CS, et al. Lasers Surg Med. 2007;39(5):381-385).

Graber et al reported an excellent safety profile for nonablative fractional resurfacing, with 7.6 percent adverse events in 961 treatments, most commonly acneiform eruptions and herpes simplex virus outbreaks despite prophylaxis (Graber EM, Tanzi EL, Alster TS. Dermatol Surg. 2008;34(3):301-307).

Sizing up CO₂ lasers

Due to their high water absorbance, ablative fractional resurfacing lasers (2,790 nm erbium yttrium scandium gallium garnet [Er:YSGG]; 2,940 nm erbium:yttrium aluminum garnet {Er:YAG]; 10,600 nm carbon dioxide [CO₂]) create microscopic treatment zones of vaporized epidermis with varying amounts of dermal vaporization and coagulation.

The Er:YAG wavelength is absorbed 12 to 18 times more efficiently than the CO₂ laser light, and therefore achieves less depth of penetration. Manuskiatti and colleagues recently evaluated the effects of these lasers on atrophic acne scars in Asian patients (Manuskiatti W, Iamphonrat T, Wanitphakdeedecha R, Eimpunth S. Dermatol Surg. Epub 3 Dec 2012). Twenty-four patients with type IV skin were treated in a split-face fashion for two laser treatments at two-month intervals and followed for six months.

Of the Er:YAG sites, 55 percent graded a greater than 50 percent improvement. The same was true for 65 percent of the CO₂ sites. The CO₂ laser caused greater discomfort. Kim reported similar findings with two treatments of the Er:YSGG laser, as 70 percent of patients had 50-89 percent improvement in acne scars (Kim S. Dermatol Surg. 2011;37(10):1464-1469).

Hedelund et al evaluated the effects of CO₂ laser on atrophic acne scars and found that two monthly unilateral treatments resulted in a statistically significant improvement in scar texture and atrophy when compared to the contralateral untreated control side (Hedelund L, Haak CS, Togsverd-Bo K, et al. Lasers Surg Med. 2012;44(6):447-452).

Studying scar improvements

Ong et al recently performed an elegant review of 26 studies of fractional lasers for acne scars published from 2003 to 2011 (Ong MWS, Bashir SJ. Br J Dermatol. 2012;166(6):1160-1169). The authors noted challenges to their work including the wide variety of parameters and devices used, the fact that most studies did not have a control or comparison group, and the subjective nature of scar rating scales.

Despite these limitations, the authors concluded that fractional laser resurfacing does improve acne scars. Ablative fractional resurfacing is associated with erythema for three to 14 days and a high risk of PIH that usually lasts for one month but can persist for up to six. In contrast, nonablative fractional resurfacing results in erythema for one to three days that should resolve within a week and a lower risk of PIH.

Scar improvement with ablative fractional resurfacing ranged from 26-83 percent, whereas scar improvement with nonablative fractional resurfacing was 26-50 percent. The authors called for double-blind, split-face randomized controlled trials with objective scar assessment and histology to better understand the effects of fractional laser resurfacing on acne scars.

Realistic goals

This data underscores the importance of setting realistic expectations. Explaining to patients that lasers are not scar erasers, and that a series of laser and/or other interventions will be necessary to achieve a perceptible improvement, helps to create a therapeutic alliance.

Like many conditions we encounter in dermatology, acne scars are best treated with a multimodal approach. Punch and surgical excision, subcision, the trichloroacetic acid CROSS technique, dermal fillers, intralesional corticosteroids and dermabrasion can all serve as useful adjuncts to laser and light therapy (for a comprehensive review see: Goodman G. Dermatol Surg. 2012;38(8):1302-1309).

We as dermatologic surgeons have the opportunity to customize therapy for our acne scar patients and dramatically enhance their quality of life. DT

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