2006 ANNUAL SCIENTIFIC SEMINAR MODERN LASER THERAPY: THEORY, PRACTICE & THE INTERFACE WITH TOPICALS Eric F. Bernstein, M.D. Department of Dermatology University of Pennsylvania 405 Modern laser therapy originated over two decades ago, as the theory of selective photothermolysis was born. The last decade has seen an exponential increase in the number of devices available for skin treatment. Many lasers are available for treating each skin condition including: photoaging, rosacea, spider veins, port-wine stain birthmarks, scars, striae, brown spots, tattoos, unwanted hair and many other conditions. In addition, new areas of research including: cellulite and fat treatment, acne treatment and lasers for improving penetration of topical products to name a few. Keeping up with these advances in technology requires an understanding of not only laser physics, but biology as well. Paralleling this explosive growth in laser technology has been an equivalent growth in the chemistry of topical skin treatments. Topicals are used hand-in-hand with lasers to achieve the desired endpoints. Only by studying the combined benefits of topical treatments and lasers can maximum benefits be achieved. The future will see smart lasers that detect targets in the skin and adjust settings accordingly, used with topical agents that dramatically improve the results achieved through laser treatment. This presentation will review the various conditions treated by laser surgery. The earliest lasers used for the treatment of skin were the pulsed-dye lasers for treating port-wine stain birthmarks. These lasers were developed following landmark manuscripts in 1981 and 1983 describing selective photothermolysis: the concept of removing target tissue within skin, while leaving the surrounding skin unaffected. This concept relies on selecting a wavelength of light preferentially absorbed by the target tissue (blood vessels, pigment-containing cells, etc.). In addition, the pulse-duration of the administered light must be selected according to the size of the target structures. The time required for light to heat up the target must not be exceeded by enough time to allow heat to diffuse to surrounding skin, damaging it and leading to a scar. The first major application of this technology was for treating port-wine stain birthmarks. The earliest lasers were very slow, using small spot sizes that limited the effectiveness of these devices. Nonetheless, they were a major breakthrough in technology offering removal of vascular birthmarks without scarring for the first time. Continued innovation of this technology has lead to improvements in port-wine stain removal, and made possible the removal of numerous other vascular lesions. Cherry hemangiomas, linear telangiectasias, rosacea, erythematous scars, lower extremity spider veins and even acne have been treated with pulsed-dye lasers.

406 JOURNAL OF COSMETIC SCIENCE Following the pulsed-dye laser, solid state, synthetic crystal lasers such as the ruby, alexandrite and Nd:YAG lasers were developed. These lasers are mainly used for the treatment of pigmented lesions such as: tattoos, freckles and lentigos, and pigmented birthmarks like Cafe au Lait macules and Nevus of Ota and Ito. These lasers have very short pulse durations in the nanosecond domain. Longer pulse duration Nd:YAG lasers using a KTP doubling crystal to increase the frequency and half the wavelength from 1064 nm to 532 nm have been developed for treating linear veins that occur commonly on the face and legs. The next major innovation in laser development were lasers to selectively remove hair by stimulating an inflammatory response causing a prolonged telogen phase of hair growth. These lasers used relatively long pulse durations in the millisecond domain, and long wavelengths not absorbed by hemoglobin that could penetrate to reach the entire hair shaft. In addition, these lasers use large spot sizes for increased depth of penetration. The innovations in facial rejuvenation have been the broadest. Radiofrequency, infrared lasers including diode lasers, intense pulsed light sources (IPLs) and numerous other devices emitting electromagnetic radiation have been used to rejuvenate and tighten skin. In addition, lasers have developed to target fat to reduce cellulite and possibly dissolve fat without the need for liposuction. The recent explosion in laser development reflects society's increasing age and its increasing desire to hide its advancing age. Topical products play a pivotal role in augmenting lasers' effects, as well as in reducing the likelihood of temporary and permanent side-effects. Lasers that ablate the skin surface such as the erbium or carbon dioxide lasers used for skin resurfacing, or the q-switched lasers used for removal of tattoos or pigmented lesions require both pre- and post-treatment to minimize the risk of post-treatment hyperpigmentation and scarring. Permanent hypopigmentation is a late side-effect of these lasers that is still poorly understood. Even non-ablative laser treatments such as laser hair removal, vascular lesion removal, or non-ablative rejuvenation benefit from intelligent use of topicals pre- and post­ treatment. Carefully considered topical treatment regiments can reduce side effects and augment the benefits of laser treatments.