Laser Treatment of Scars

Keywords:Laser, fiber,  Time:28-10-2015

ABSTRACT

Over the past decade, refinements in laser technology as well as advances in laser techniques have enabled dermatologic surgeons to define the most appropriate lasers to usefor different scar types without the adverse sequelae and recurrence rates noted with older surgical revision techniques and continuous wave laser systems.

Scar Characteristics

Proper scar classification is important because differences in clinical scar characteristics determine the treatment protocol. 1 Scar color, texture, and morphology, as well as previously applied treatments, will affect the laser parameters and number of treatments required for optimal improvement.v' See Table 1.
Hypertrophic scars are raised, finn, erythematous scars formed as the result of overzealous collagen synthesis coupled with limited collagen lysis during the remodeling phase of wound healing. The result is the formation of thick, hyalinized collagen bundles consisting of fibroblasts and fibrocytes. Despite the obvious tissue proliferation, hypertrophic scars remain within the confines of the original integument injury and may regress with time.Significant improvement in hypertrophic scars is generally noted within a couple ofPDL treatments. (See Figures lA, IB) Although thick keloids may require the simultaneous use of intralesional corticosteroid or 5-fluorouracil injections to enhance clinical results, the adjunctive use of intralesional corticosteroids does not significantly enhance the clinical improvement seen after PDL treatment in all but the most symptomatic or proliferative hypertrophic scars.'
Adjacent, non-overlapping laser pulses at fluences ranging 6.0-7.5J/cm2 (7mm spot) or 4.5-5.5J/cm2 (lOmm spot) should be applied over the entire surface of the scar. Energy densities are decreased by 10% inpatients with darker skin phototypes or for scars in delicate locations (e.g., the anterior chest). With PDL irradiation, the patient experiences a snapping sensation similar to that of a rubberband. Post-treatment, a mild sunburn-like sensation is produced for 15-30 minutes that is generally well-tolerated; however, some patients may require application of an ice pack. Fig lA Hypertrophic scars on upper lip before treatment
The most commonly experienced side-effect of 585nm PDL treatment is post-operative purpura, which can persist for several days. Swelling of treated skin may occur immediately after laser Fig 1B irradiation, but generally Scar improvement seen subsides within 48 hours. after PDL treatment Strict sun precautions should be practiced between treatment sessions in order to avoid stimulating pigment production in the treated areas. Subsequent laser sessions should be postponed until any excess pigment has resolved, so that the presence of epidermal melanin does not compromise the effectiveness ofthe laser.Topicalbleaching agents may be used to hasten pigment resolution. Treatments are typically delivered at 68 week intervals; however, longer treatment intervals may be necessary for adequate healing in those patients with darker skin phototypes who develop significant postoperative hyperpigmentation. Laser Treatment ofAtrophic Scars Ablative Laser Skin Resurfacing
Facial atrophic scars can be safely and effectively resurfaced through the proper use of a high-energy, pulsed or scanned carbon dioxide (C02) or Erbium-YttriumAluminum-Gamet (Er:YAG) laser.2,3,8-11 These laser systems emit high energy densities within extremely short pulses that effect tissue vaporization with limited thermal conduction to non-targeted surrounding skin. Since each laser pass effects a predictable and reproducible amount of tissue vaporization and residual thermal damage, as much or as little tissue can be removed as required by the type of scar being treated.
Atrophic scarresurfacing with aCO2 laserhas effected scar improvements of 50%_80%.8-10A predictable amount of epidermis and papillary dermis is vaporized by a typical CO2 laser resurfacing procedure, with tissue vaporization depths of 20-60j.lmand zones of thermal necrosis ranging another 20-50j.lm. Immediate collagen shrinkage with subsequent collagen remodeling accounts for many of the clinical benefits observed after ablative laser skin resurfacing.

More recently, pulsed Er:YAG lasers have also been used for the treatment of atrophic scars.lO,ll The short-pulsed Er:YAG laser was developed as a less aggressive alternative to CO2 laser skin resurfacing. The 2940nm wavelength emitted by theEr:YAG laser corresponds to the peak absorption coefficient of water and is absorbed 12-18 times more efficiently by superficial, water-containing tissue than does the I0,600nm wavelength ofthe CO2 laser. With a pulse duration of 250j.lsec, a typical short-pulsed Er:YAG laser ablates 10-20j.lm of tissue per pass at a fluence of 5J/cm2 and produces a residual zone of thermal injury not exceeding ISum, The precise tissue ablation and limited residual thermal damage result in a faster postoperative recovery and improved side-effect profile as compared to CO2 laser skin resurfacing.v" However, because of the limited zone of thermal injury, short-pulsed Er:YAG laser skin resurfacing is hindered by poor 'intraoperative hemostasis, limited collagen contraction, and substantially less impressive clinical results than with CO2 laser skin resurfacing.

To overcome the limitations of short-pulsed Er:YAG laser skin resurfacing, "modulated" or "dual-mode" (short- and long-pulsed) Er:YAG systems have been developed that combine ablative and coagulative pulses to produce deeper tissue vaporization, greater contraction of collagen, and improved hemostasis. Studies have demonstrated significant clinical improvement in atrophic scars with these modulated laser systems.i-"
Whether a CO2 or modulated Er:YAG laser system is used to treat atrophic facial scars, the goal of treatment is to soften depressions and stimulate neocollagenesis in order to fill in the residual defects. (Figures 2A,B) For a small number of grouped scars, spot laser resurfacing may be a viable option. For more extensive and diffuse scarring, laser treatment should be performed with a scanning handpiece over the entire cosmetic unit in order to prevent obvious lines of demarcation between treated and untreated sites. With the CO2 laser, a fluence of 300mJ is typically used to effect epidermal ablation with one pass. A dual-mode Er:YAG laser operated at a fluence of 22.5J/cm2 achieves comparable results with a single pass. However, most atrophic scars will require multiple laser passes, regardless of the laser system used. Between each laser pass, the partially desiccated tissue must be completely removed with saline- or water-soaked gauze to prevent excessive thermal necrosis in residual tissue.

molysis, radiofrequency technology produces an electric current that generates heat through resistance inthe dermis and subcutaneous tissue, thus stimulating neocollagenesis and collagen remodeling. Preliminary studies" de~onstrate promise in the treatment of acne and, potentially, acne scarring. Further investigation is warranted to determine the role of this novel device in the treatment of atrophic facial scars.

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