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Nonablative Skin Therapies

Although there has always been interest in looking younger, with the introduction of the carbon dioxide (CO2) laser for the treatment of photoaged skin, increasing numbers of patients are being lured to the plastic surgeon's office who are not yet ready for a cold steel surgical solution for dynamic and static rhytids. The ablative effect of the CO2 laser on the epidermal skin surface combined with the thermally induced collagen remodeling of the underlying dermis provides a solution for the pigmentary and structural changes associated with photoaged skin. The impressive early treatment results using the CO2 laser gave rise to nonablative technologies seeking to minimize epithelial damage while retaining the beneficial property of subsurface collagen remodeling. Consumer and physician interest in "minimal downtime" techniques of facial rejuvenation has driven the development of numerous laser and nonlaser light sources that reverse the process of photoaging. Because nonablative photorejuvenation leaves the epidermis intact, patients can return to their normal lifestyles almost immediately after treatment, and the complications associated with ablative techniques (infection, postoperative edema, persistent erythema, and long-term dyspigmentation) are avoided. Nevertheless, clinical improvement is limited when nonablative techniques are used as the sole treatment modality. Patient and physician satisfaction is high with the nonablative techniques. When they are combined with neuromodulation, soft tissue fillers, and home skin care, the results can approach those of more invasive ablative laser therapies. This article describes the currently available nonablative technologies with respect to their mechanism of action and clinical use.

Pathophysiology of ultraviolet light-induced skin damage

The typical changes associated with aging skin can be attributed to intrinsic (genetic) and extrinsic (environmental) factors. Cumulative exposure to sun remains the largest factor in aging skin and is responsible for most of the unwanted aesthetic effects. Photoaged skin is characterized by rhytids, laxity, uneven pigmentation, lentigines, sallow color, telangiectasias, increased pore size, and a leathery appearance. In contrast, chronologically aged skin that has been protected from the sun is thin and has reduced elasticity but is otherwise smooth and unblemished. Dermal damage induced by ultraviolet irradiation is principally manifested histologically as the disorganization of collagen fibrils and the accumulation of elastin-containing material (solar elastoses). The collagen fibers in the upper dermis are destroyed over time and are gradually replaced by an amorphous material that is associated with an increase in reticulin fibers. The amount of elastoic material and associated fiber breakdown is probably responsible for the fine rhytid formation associated with sun-damaged skin [1]. Immunohistochemical analysis of chronically photodamaged skin reveals sustained elevation of matrix metalloproteinases. Matrix metalloproteinases are critical factors in the remodeling of the extracellular matrix during development and wound healing and are responsible for the specific degradation of collagens, elastin, and other proteins in connective tissue and bone. They are believed to initiate the molecular pathway underlying the histologic changes seen in photodamaged skin [2].

Photorejuvenation and the reversal of photoaging effects

Nonablative photorejuvenation of human skin is a procedure designed to confine selectively, without any epidermal damage, thermal injury to the papillary and upper reticular dermis, leading to fibroblast activation and synthesis of new collagen and extracellular matrix material (neocollagenesis). The skin surface is not removed or modified; instead, dermal "remodeling" or '"toning" as a wound healing response is initiated to regenerate subsurface collagen. Photorejuvenation can span a broad range of wavelengths, light sources, and target chromophores but can generally be divided into thermal and nonthermal mechanisms [3]. In general, photorejuvenation uses electromagnetic radiation to generate thermal injury in target tissues. Selective heating is achieved owing to light energy being taken up by specific absorption molecules (chromophores) such as water, melanin, and hemoglobin. The laser energy absorbed by the target chromophore is then diffused in the form of heat to damage deeper surrounding tissues, inducing the wound healing response. Hemoglobin has significant light absorption in the violet, blue-green, and yellow portions of the spectrum. The wavelengths suitable for targeting hemoglobin are in the absorption bands of 577 to 595 nm. Epidermal melanin is the dominant chromophore in human skin. Melanin is particularly concentrated in the basal layer, typically 50 to 100 urn below the skin surface. Melanin absorption is highest in the ultraviolet portion of the spectrum but also significantly absorbs the visible and near-infrared wavelengths. Subsequent heat conduction to adjacent dermal collagen may give rise to the observed histologic changes necessary for nonablative photorejuvenation [4]. Laser-induced thermal injury should be confined to a zone 100 to 500 urn below the skin surface where the majority of solar elastoses in photodamaged skin occur. More superficial injury may be ineffective for rhytid reduction; deeper injury may result in scarring [4].

Photomodulation is the term used to describe another form of nonablative technology that uses low-level light energy to stimulate directly upregulation of collagen deposition by fibroblasts. No heat is produced in the dermal layers. The proposed mechanism is that photons are absorbed directly by fibroblast mitochondria, increasing cell activity and production of collagen [3].

Patient selection and indications

Matching the patient to the appropriate photorejuvenative modality is the key to success in treatment of photodamaged skin. Many methods of patient assessment are available, but the most useful include the Fitzpatrick skin type classification (Table 1) and the Glogau photoaging scale (Box 1). Although these parameters become more important when the clinician is considering ablative interventions for skin resurfacing, an understanding of these criteria is important when discussing the expectations and limitations of nonablative techniques with the patient. The Fitzpatrick sun-reactive skin type gives a good indication of potential dyschromia following epidermal/papillary dermal injury, the likelihood of developing postinflammatory hyperpigmentation during the early postoperative period, and the potential for permanent hypopigmentation as the result of melanocyte destruction [1]. In general, patients with Fitzpatrick skin types I to III tolerate resurfacing procedures with minimal risk of color change. Resurfacing should be undertaken cautiously in patients with Fitzpatrick skin types IV to VI. The Glogau photoaging scale categorizes photodamage based on rhytid formation to guide the practitioner in selecting the appropriate resurfacing procedure based on the lines and wrinkles that one wishes to correct. Glogau classifies photoaging as type I, "no wrinkles"; type II, "wrinkles in motion"; type III, "wrinkles at rest"; and type IV, "only wrinkles" [1]. Patients with photoaging type I are not suitable candidates for aggressive interventions, nor are patients with photoaging type IV well served by superficial techniques.

Box 1 . Glogau photoaging classification [1]

Classification of lasers and light sources

Numerous noninvasive techniques exist for rejuvenating facial skin (Table 2). These technologies can be separated into three categories: (1) those that improve skin texture and pigmentation (intense pulsed light, light-emitting diodes, nonablative neodynium: yttrium-aluminum-garnet [Nd:YAG] laser, 1540 nm erbium:glass [Er:glass] laser, pulsed dye laser, Fraxel laser); (2) rhytid ablation (2940 nm Er:YAG laser, CO2 laser, Fraxel laser); and (3) skin-tightening methods (Fraxel laser, Thermage, Titan laser).

Clinical applications and uses of lasers and light sources for photorejuvenation

• 1320 nm Neodynmiuin:yttrium-aluminum-garnet
• 1064 nm Q-switched neodynmium: ytrium-aluminum-garnet
• Fraxel laser
• 1540 nm Erbium:glass laser
• 585 nm Pulsed dye laser
• Intense pulsed light
• Light-emitting diodes
• Radiofrequency device: thermalifting
• Titan 1100 to 1800 nm infrared laser

Summary

With the expanding variety of therapies available for patients seeking facial skin rejuvenation, the physician must appreciate the indications, complications, benefits, and limitations of each technique. Nonablative photorejuvenation offers a new approach in treating photodamaged skin. Practitioners of nonablative skin remodeling have advocated serial treatments to achieve a gradual cumulative improvement. Collagen deposition occurs over a period of several months; therefore, the final cosmetic appearance is not immediately evident. Patients often describe an improvement in skin tone after nonablative laser treatment. The ease of treatment, minimal discomfort, and limited sideeffect profile make nonablative laser remodeling an appealing addition to the cosmetic surgeon's armamentarium. The drawback of these positive features is mild cosmetic improvement. Subtle enhancements may be acceptable to some patients. Nonablative laser resurfacing is an excellent option for patients who are unwilling to risk the side effects of ablative resurfacing techniques or to pay for these more expensive procedures, which may require time off for a lengthy recovery. Proper patient evaluation and counseling will lead to optimal patient satisfaction. With the continued focus on facial skin rejuvenation, nonablative techniques should continue to evolve and meet the demands of an evergrowing and sophisticated patient population.

References

[1] Glogau RG. Aesthetic and anatomic analysis of the aging skin. Semin Cutan Med Surg 1996;15(3):134-8.

[2] Fisher GJ, Wang ZQ, Datta SC, et al. Pathophysiology of premature skin aging induced by ultraviolet light. N Engl J Med 1997;337(20):1419-28.

[3] Weiss RA. McDaniel DH. Geronemus RG. Review of nonablative photorejuvenation: reversal of the aging effects of the sun and environmental damage using laser and light sources. Semin Cutan Med Surg 2003; 22{2):93-106.

[4] Ragland HP, McBurney EL Complications of resur­facing. Semin Cutan Med Surg I996;15(3):200-7.

[5] Goldberg DJ. Full-face nonablative dermal remodeling with a 1320 nm Nd:YAG laser. Dermatol Surg 2000; 26(10):915-8.

[6] Bosniak S, Cantisano-Zilkha M. A combined approach to noninvasive facial rejuvenation: home care, peels, neuro-modulation, and laser-assisted subsurface collagen remodeling. Operative Techniques in Oculoplastic Orbital and Reconstructive Surgery 2001;4(2):65-8.

[7] Hardaway CA, Ross EV. Nonablative laser skin remodeling. Dermatol Clin 2002;20(1):97-111. [8] Reliant Technologies Web site. Available at: www.

reliantlaser.com. Accessed October 31, 2004. [9] Fournier N, Dahan S, Barneon G. et al. Nonablative remodeling: clinical, histology, ultrasound imaging, and profilometric evaluation of a 1540 nm Er:glass laser. Dermatol Surg 2001;27(9):799-806.

[10] Bjerring P, Clement M, Heickendorff L, et al. Selective nonablative wrinkle reduction by laser. J Cutan Las Ther 2000;2:9-15.

[11] Ottini J. Photorejuvenation with intense pulsed light: combination treatments. Operative Techniques in Oculoplastic Orbital and Reconstructive Surgery 2001; 4(2):69-73.

[12] Sadick NS, Weiss RA. Intense pulsed-light photo-rejuvenation. Semin Cutan Med Surg 2002;21{4): 280-7.

[13] Munavalli GS, Weiss MA, Weiss RA. The use of intense pulsed light for full facial rejuvenation. In: Bosniak S, Cantisano-Zilkha M, editors. Minimally invasive techniques of oculofacial rejuvenation. New York: Thieme Publishers; 2005. p. 7-11.

[14] Bitter PH. Noninvasive rejuvenation of photodamaged skin using serial, full-face intense pulsed light treat­ments. Dermatol Surg 2000;26(9):835-43.

[t5] Lightbioscience company Web site. Available at http://www.lightbioscience.com/gwfactsheet.hlm. Accessed October 31, 2004.

[16] Hsu TS, Kaminer MS. The use of nonablative radio-frequency technology to tighten the lower face and neck. Semin Cutan Med Surg 2003;22(2):115-23.

[17] Bosniak S, Cantisano-Zilka M. Therma-lifting of the face, neck and brows. Operative Techniques in Oculo­plastic Orbital and Reconstructive Surgery 2001;4(2): 113-8.

[18] Bosniak S. Introduction to alternative techniques of oculofacial rejuvenation. In: Bosniak S, Cantisano-Zilkha M, editors. Minimally invasive techniques of oculofacial rejuvenation. New York: Thieme Publish­ers; 2005. p. 1-6.

[19] Cutera company Web site. Available at: http://www. cutera.com/prodappps/product. Accessed January 1, 2005.

Lisa A. Zdinak, MD*, Michael E. Summerfield, MD

Georgetown-Washington National Eye Center.
110 Irving Street, NW, Suite IA-19, Washington, DC 20010, USA