Nonablative skin tightening with a variable depth heating 1310-nm wavelength laser in combination with surface cooling

Journal of Drugs in Dermatology, Nov, 2007 by Macrene Alexiades-Armenakas

Abstract

A near-infrared laser with the ability to target different depths within skin has been developed and evaluated for the application of facial and neck skin tightening in a pilot clinical study. The device consists of a combination of a 1310-nm wavelength and sapphire contact cooling. Cooling temperature and laser pulse duration were varied to target different dermal depths in various subgroups of the subject population. Quantitative changes in various categories characterizing the aging skin employing a comprehensive grading scale as well as subject satisfaction were calculated. A mean improvement of 7.9% (95% CI [confidence interval] 3.6-12.3) in laxity and 10.6% (95% CI 5.8-15.4) in rhytides was determined by quantitative grading at one month after the treatment regimen. These values were 11.0% (5.5-16.5) and 11.7% (5.8-17.7) at 3 months after the treatment regimen. The percent of patients reporting mild or better improvement in laxity of the face and neck was 78% and 61% at one month, and 63% and 61% at 3 months, respectively. The discomfort was minimal. Side effects were limited to short-term erythema and edema. In summary, a variable depth heating laser can achieve skin tightening and wrinkle reduction with high subject satisfaction.

Introduction

Laser and light-based treatments for wrinkle reduction, skin tightening, and improvement in photoaging have included ablative laser resurfacing using the C[O.sub.2] and Er: YAG lasers, fractional laser resurfacing, and nonablative lasers and light devices. These modalities rely on thermally or chemically damaging tissue with resulting collagen contraction and new collagen formation. (1,2) Though ablative modalities produce excellent results, long lasting erythema, 2- to 3-week healing times, risk of hyperpigmentation, infection, and scarring make them unattractive to patients and physicians. (1) While the advent of fractional laser resurfacing has decreased healing times to 2 to 3 days, results are in the moderate range and multiple treatments are necessary. (3) Nonablative techniques such as subsurface heating with light (4-6) and radiofrequency energy (7-14) or a combination of light and radiofrequency energy (15-16) are associated with the least risk and extremely rapid recovery times, though offering more modest results. These procedures are becoming increasing popular due to their minimal risk and ultra rapid recovery, in the setting of acceptable improvement.

Among the nonablative procedures, monopolar radiofrequency current in combination with skin surface cooling has undergone modifications over time to treat with reasonably low discomfort levels and low risk of side effects, while achieving acceptable results. (17) Bipolar radiofrequency current and, most recently, unipolar radiofrequency as electromagnetic radiation have shown to be safe and effective with minimal discomfort. (12-14) Several published reports with encouraging results also exist for treatments with an infrared (1100- to 1800-nm) heating lamp in combination with surface cooling. (18-20) These devices are based on the principle of skin surface cooling combined with energy delivery to cause bulk heating of skin underneath the skin surface.

Despite these advances, there is a belief amongst physicians that the amount of improvement and the fraction of patients showing improvement leave room for improving such treatment modalities. As a response, a novel laser-based device that can heat various depths within the skin has been developed, which is the topic of evaluation in this study. This device has been theorized to heat different levels within skin, dependent on the cooling temperature and duration as well as the laser pulse duration. This theory of variable depth heating has been supported by Monte Carlo simulations of light distribution followed by heat transfer calculations and thermal injury estimates based in the temperature-time history, as well as histological analysis of in vitro pigskin by Paithankar and Ross. (21) The results reported in the study indicated that the thickness and mean depth of the thermally damaged subsurface zone can be controlled by choice of surface cooling and 1310-nm irradiation times. This potentially introduces new methods to treat various skin conditions, the pathology of which may reside at different depths within skin. Another important aspect to the current device is that it does not require anesthesia and is associated with minimal discomfort. This device heralds a new generation of laser resurfacing devices that save time and the cost involved in anesthesia and offer less patient discomfort.

The scope of the current clinical study is the evaluation of this novel variable depth heating device for the treatment of laxity and rhytides of the face and neck. Twenty subjects presenting with lax facial and neck skin were randomized to 3 subgroups for full-face treatments employing parameters targeting the superficial, mid, and deep dermis. Their responses at 1 and 3 months after the last treatment in improvement in rhytides, laxity, other signs of photodamage, and self-satisfaction have been evaluated and reported.