Fractional Laser Resurfacing for Acne Scarring in Patients with Fitzpatrick Skin Types IV–VI

By Andrew F. Alexis MD MPH

INTRODUCTION
Traditional methods for skin resurfacing (including medium to deep chemical peels, Er:YAG and CO2 lasers, and dermabrasion) are associated with a substantial risk of dyspigmentation and, in some patients, keloidal scarring when performed on darker skin types (Fitzpatrick skin phototypes IV–VI). Fractional non-ablative lasers have emerged as a safer treatment option for resurfacing richly pigmented skin due to the considerably lower rate of the above complications when appropriate parameters are used.

BACKGROUND
Previous studies involving Asian subjects have shown that the risk of hyperpigmentation associated with nonablative fractional laser resurfacing in skin of color is increased with higher treatment densities,1,2 which refers to the density of microthermal zones of thermal injury per square centimeter (MTZ/cm2). For this reason, the author recommends conservative treatment densities for patients with Fitzpatrick skin types IV–VI. Safe treatment levels for the treatment of acne scarring in this population typically range from 4 (200 MTZ/cm2 – 11%) to 8 (456 MTZ/cm2 – 23%) at an energy of 40 mJ. A recent retrospective study of Chinese patients treated with the 1,550 nm erbium-doped fractional laser (Fraxel 1550, Solta Medical) found that using fewer passes per treatment, but increasing the total number of treatments was associated with a lower risk of postinflammatory hyperpigmentation without compromising efficacy.3 Pre-treatment with hydroquinone may also help to reduce the incidence of hyperpigmentation post-fractional laser resurfacing.4 The current author pre-treats with hydroquinone 4% cream to the full face beginning two weeks prior to fractional laser treatment. The hydroquinone is discontinued for seven days post laser (due to potential irritation) and resumed for four weeks thereafter. A broad spectrum sunscreen with an SPF of at least 30 is used and sun avoidance is advised.

Studies using ablative fractional CO2 lasers for acne scarring in skin of color have reported considerably high rates of post-treatment hyperpigmentation,5 and therefore, fractional non-ablative lasers are strongly preferred over fractional ablative lasers for Fitzpatrick skin types IV–VI in this author’s opinion.6

SETTINGS AND METHODS
In a randomized, split-face, comparative, investigator-blinded study conducted by Alexis et al.,7 subjects with Fitzpatrick skin phototypes IV–VI with acne scars had four monthly treatments with the non-ablative fractional laser (Fraxel 1550, 1,550 nm) using a low density setting (200 MTZ/cm2 – 11%; treatment level 4) on one side of the face and a higher density setting (392 MTZ/cm2 – 20%; treatment level 7) on the other, keeping the energy constant on both sides at 40mJ. Hydroquinone 4% cream was used two weeks prior to the first treatment and continued for one month after the last treatment. At six months (three months after the final treatment), greater improvement in acne scarring by blinded investigator Visual Analog Score was found on the side of the face treated with the higher density setting and no residual hyperpigmentation was observed in any subjects. There was no difference in the incidence of temporary hyperpigmentation when both settings were compared. The settings and treatment precautions used in one case of a 40-year-old Hispanic male patient with Fitzpatrick skin type IV and acne scarring who participated in the study and elected to get a “touch up” treatment were as follows:
• Pre-treatment with hydroquinone 4% cream to whole face
starting two weeks prior to treatment
• Topical anesthesia – 23% lidocaine, 7% tetracaine ointment
applied 45 minutes prior to treatment
• Energy: 40 mJ
• Treatment level 6 (17% coverage or 328 MTZ/cm2)
• Eight passes (41 MTZ/pass)
• Continuous forced air cooling (integrated into the hand
piece in this particular model of the Fraxel Re:Store)
• Post-treatment ice packs for approximately 10 minutes
• Post-treatment broad spectrum sunscreen SPF 30+ and sun
avoidance

The energy on this device correlates with the depth of the microscopic columns of thermal injury induced by the laser. Therefore, the higher the energy, the greater the depth of thermal injury. For this patient, 40 mJ (which corresponds to MTZ’s 1120μ in depth) was chosen based on the clinical severity (and depth) of the acne scars. A treatment density of 328 MTZ/cm2 (treatment level 6 – 17%) was chosen to achieve greater efficacy than his previous treatments at a lower density (treatment level 4 or 200 MTZ/cm2) while maintaining a low risk of postinflammatory hyperpigmentation and minimal downtime.

A useful treatment pearl to keep in mind is that when using higher densities, it is prudent to allow more time for cooling between passes of the laser. This is sometimes referred to as the “pawing” technique where two consecutive parallel passes are performed in the same direction, allowing for cooling between passes (as opposed to a backtracking method in which one pass is applied, followed by a second pass in the reverse direction along the same linear track). This approach helps to ensure a lesser risk for excessive bulk heating which may contribute a higher risk of hyperpigmentation post-treatment. When hyperpigmentation does occur, widening the interval between treatments is advisable, postponing the next treatment until the hyperpigmentation has completely resolved. In such cases, decreasing the treatment density on the subsequent treatments would be recommended. Alternatively, reducing the number of passes per session and performing more treatment sessions to achieve comparable efficacy could be considered (as described by Chan et al3).

CLINICAL BOTTOM LINE
In summary, fractional non-ablative laser resurfacing is a safe and effective treatment option for patients with skin of color as long as conservative parameters (especially lower treatment densities) are used. Pre-treatment and post-treatment precautions are also key to reducing the risk of pigmentary complications in this population.

DISCLOSURES
The author has no relevant financial conflicts of interest to disclose, but has received laser tips as a research grant from Solta Medical.

REFERENCES
1. Chan HH, Manstein D, Yu CS, Shek S, Kono T, Wei WI. The prevalence and risk factors of post-inflammatory hyperpigmentation after fractional resurfacing in Asians. Lasers Surg Med. 2007;39(5):381-385.
2. Kono T, Chan HH, Groff WF, et al. Prospective direct comparison study of fractional resurfacing using different fluences and densities for skin rejuvenation in Asians. Lasers Surg Med. 2007;39(4):311-314.
3. Chan NP, Ho SG, Yeung CK, Shek SY, Chan HH. The use of non-ablative fractional resurfacing in Asian acne scar patients. Lasers Surg Med. 2010;42(10):710-715.
4. Alajlan AM, Alsuwaidan SN. Acne scars in ethnic skin treated with both non-ablative fractional 1,550 nm and ablative fractional CO(2) lasers: Comparative retrospective analysis with recommended guidelines. Lasers Surg Med. 2011;43(8):787-791.
5. Chan NP, Ho SG, Yeung CK, Shek SY, Chan HH. Fractional ablative carbon dioxide laser resurfacing for skin rejuvenation and acne scars in Asians. Lasers Surg Med. 2010;42(9):615-623.
6. Manuskiatti W, Triwongwaranat D, Varothai S, Eimpunth S, Wanitphakdeedecha R. Efficacy and safety of a carbon-dioxide ablative fractional resurfacing device for treatment of atrophic acne scars in Asians. J Am Acad Dermatol. 2010;63(2):274-283.
7. Alexis A CM, Alam M, et al. A prospective randomized split-face comparison study of non-ablative fractional laser resurfacing in the treatment of acne scarring in Fitzpatrick skin phototypes IV-VI. Lasers Surg Med. 2011;43(suppl 23):939.

About the author

Andrew F. Alexis MD MPH

Director, Skin of Color Center, St. Luke’s Roosevelt Hospital, New York, NY Assistant Clinical Professor, Columbia University College of Physicians & Surgeons, New York, NY

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