Laser Management of Acne Scarring

Tiffany Kwok, MD; Jaggi Rao, MD, FRCPC

Disclosures

Skin Therapy Letter. 2012;17(2):4-6. 

In This Article

Laser Options Targeting Skin Color

Red Scars

Erythema is the result of visible dilated capillaries beneath the skin surface. The intensity of the erythema is dependent on the concentration, lumen size, and depth of blood vessels. Lasers and light sources used to decrease erythema of acne scars include the pulsed dye laser (PDL), potassium-titanyl-phosphate (KTP) laser, intense pulsed light (IPL), and neodymium:yttrium-aluminumgarnet (Nd:YAG) laser. Suggested laser settings are shown in Table 2. The number of treatments will vary according to several factors including patient response after each laser session, laser technology used, and parameters of treatment.

PDL is the gold standard for treating erythema from acne scarring.[2] This laser has an output wavelength of 585 nm or 595 nm, targeting oxyhemoglobin within red blood cells by approximating a major hemoglobin absorption peak at 577 nm. Treatments may be safely performed on all skin types and over hair-bearing areas without fear of follicular destruction. Tolerability of laser treatments is improved with dynamic cooling in the form of cryogen spray. Purpura occurs with extravasated red blood cells, indicating immediate vascular photocoagulation. It is advocated as a clinical endpoint of treatment, lasting a maximum of 7–10 days and resolving without sequelae.

The KTP, or frequency-doubled Nd:YAG laser, has an output wavelength of 532 nm, targeting the first peak of the oxyhemoglobin absorption curve. The penetrative depth of the KTP laser is confined to the papillary dermis of the skin and unsuitable for deeper vessels. KTP lasers generally cause only mild purpura and minimal postinflammatory hyperpigmentation on all skin types.

IPL systems are comprised of noncoherent light (approximately 500–1200 nm) released by a flashlamp within the device, which is then filtered to narrower ranges of wavelengths that simulate the monochromatic nature of true laser light. IPL devices have the benefit of larger spot sizes and a wider range of pulse duration and fluences, thereby allowing for treatment at greater depth and faster speed, coverage of larger surface areas, and concurrent therapy of multiple conditions. However, specificity for treating a single condition may be poor due to absorption competition from multiple tissue targets. Postinflammatory hyperpigmentation in darker skin types may be seen with IPL therapy.[3]

Nd:YAG lasers may be useful for treating erythema in scars with dilated blood vessels in the deep dermis. New microsecondpulsed Nd:YAG lasers are of benefit for targeting superficial dermal vessels due to the short pulse duration, low fluence, and quick repeated laser bursts.

Brown Scars

Hyperpigmentation of acne scars is common, particularly with darker skin types. Lasers used to treat scar hyperpigmentation include IPL, quality-switched (Q-switched), microsecond-pulsed Nd:YAG, both confluent and fractionated ablative erbium:YAG (Er:YAG), and yttrium-scandium-gallium-garnet (YSGG). Suggested laser settings are presented in Table 3. Concomitant use of lightening creams and sunscreen, as well as sun avoidance, is advocated to further reduce scar contrast with surrounding skin.

IPL devices, with their ability to vary output wavelength, pulse duration, and fluence, can treat several skin conditions including superficial pigmentation.[3] Care must be taken to protect the epidermis from overheating, which may cause pigment incontinence and further hyperpigmentation. Parallel cooling (extracting heat from the epidermis during the light pulse) is usually provided through the use of a sapphire window handpiece that generates surface cooling to approximately 5°C.

Q-switched lasers have the unique property of extremely short pulse durations, thereby allowing these devices to target very small pigment cells and particles, such as melanocytes, with minimal competition from the hemoglobin absorption curve. The Q-switched lasers, i.e., ruby (694 nm), alexandrite (755 nm), and Nd:YAG (1064 nm), are useful for treating skin pigmentation.[4] The endpoint of treatment is mild superficial crusting. Care must be taken to use the lowest energy settings possible to achieve pigment reduction, as too much energy may result in punctate bleeding, cell rupture, scarring, and increased pigmentation.

Microsecond-pulsed Nd:YAG lasers (1064 nm) target both melanin pigment and small blood vessels to reduce erythema and stimulate collagen production without inducing injury to surrounding tissue. This laser may be used for any skin type.[5]

Confluent laser treatment involves laser light striking the entire surface of the skin in a given area, whereas fractionated laser therapy creates microscopic thermal wounds while sparing adjacent tissue over the targeted site.[6] Confluent ablative Er:YAG (2940 nm) and YSGG (2790 nm) lasers have tremendous water absorption capacity, translating into vaporization of surface tissue with minimal collateral heating, limited damage to surrounding tissue, and reduced risk for further hyperpigmentation.[7] These lasers ablate approximately 30 microns of the epidermis, inducing exfoliation and improving superficial hyperpigmentation. Test spots should be performed when using any ablative laser on darker skin.

Fractionated ablative Er:YAG and YSGG lasers release light energy at high peak power to create channels in skin tissue.[6] These channels are physically ablated, leaving true air channels that allow removal of surrounding pigment via transepidermal elimination.

White Scars

Ultraviolet (UV) light stimulates melanogenesis in areas where melanocytes are intact. UV light can stimulate the migration of melanin-producing cells to melanocyte-deficient areas, increasing pigment in these regions.[1] Excimer (excited dimer) lasers have a wavelength in the UV range (308 nm), providing concentrated melanin stimulation to white scars.

Fractionated ablative lasers (Er:YAG, YSGG, and carbon dioxide) create air channels that ultimately contract to reduce the surface area of the white scars, making them appear smaller in diameter.[7]

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