Histopathological Changes After Experimental Skin Resurfacing Using an Improved Fractional High-Power 1064-nm Q-Switched Nd:YAG Laser

December 2019 | Volume 18 | Issue 12 | Original Article | 1261 | Copyright © December 2019

Fernando Urdiales-Galvez MD,a Mario A. Trelles MD PhD,b Sandra Marten-Sanchez MD,aMonica Maiz-Jimeanez MDa

aInstituto Médico Miramar, Málaga, Spain bVilafortuny Laser Centre, Dubai, United Arab Emirates

Abstract
BACKGROUND: Several studies confirm microscopic changes in the cutaneous architecture following various rejuvenation techniques using non-ablative lasers Objective: To investigate the histological changes that occur after the application of an improved high-power 1064-nm fractional Q-switched Nd: YAG laser, using different focusing tips.

MATERIAL AND METHODS: Experimental skin resurfacing of the retroauricular area in 15 female volunteers, in three treatment sessions of one pass each, using the Clear Lift® laser (Alma Lasers, Israel) and five different focusing tips. Biopsies were taken before and immediately after the first treatment session, one month after the first session, and one month after the third session. A total of 60 microscopic images were evaluated at a micrometric scale.

RESULTS: The five tips used caused characteristic and similar histological changes in both the dermis and the epidermis. The signs of thermal damage and the formation of new collagen were observed at different depths, in accordance with the focal length of each tip. Neo-formation of collagen with the increase, reorganization and compaction of fibers began one month after the first treatment session, and was blindly confirmed, with all the tips used, one month after the third treatment session.

CONCLUSION: The skin takes on a new conformation, with histological signs of skin rejuvenation, concordant with previous clinical observations.

J Drugs Dermatol. 2019;18(12):1261-1266.

INTRODUCTION

In 2012, the first clinical results were presented with a new fractional non-ablative Q-switched neodymium-doped YAG (Nd:YAG) 1064-nm laser, which combines the benefits of a non-ablative and fractional laser. The facial resurfacing treatments were effective, practically painless, and without downtime. In three treatment sessions, fine lines and wrinkles were reduced by 11.3% without adverse effects (besides temporary edema and erythema, and some cases of pinpoint petechiae) following multiple passes using energies between 400 and 1200 mJ/pulse. The procedure was extraordinarily safe and without downtime.1 Subsequently, Gold et al presented the results of a more detailed study using the same laser, in a sample of ten women, including much higher improvement percentages: 70% for hyper-pigmentation, 80% for telangiectasia, 80% for laxity, and 60% for actinic keratosis. The maximum fluence was also 1200 mJ/pulse, but he performed four treatment sessions.2

It has been postulated that the action of this laser is due to subdermal heating of the skin, and of the underlying extracellular matrix, causing contraction and tightening of the skin. To argue this effect, it should be noted that the focal point of the conventional Q-Switched Nd:YAG 1064-nm laser had been aimed at the surface of the skin to target melanin pigment, thereby necessitating its application in defocused mode to avoid crusting and splatter. Comparatively, the new laser has a focal point of 100 μm, just beneath the epidermis, with greater penetration and the absence of epidermal crusting. Since the wavelength is applied directly to the skin surface instead of in defocused mode, a penetration depth of up to 3.5-4mm is expected, which may also play a role in the increased efficacy compared with prior modalities.1 On the other hand, it has been suggested, based on what is known about theoretically similar lasers, that the most important effects are due to a micro-thermal injury in the dermis that causes a proliferation of fibroblasts and stimulates new collagen formation, thickening the dermis and improving skin firmness and texture.2 Despite the extensive clinical experience of results with this device, its possible effects on the cutaneous architecture at a microscopic level have not yet been investigated.

Here, we analyze biopsies taken from female volunteers treated with the same laser used by other authors,1,2 recently perfected to allow double the maximum energy per pulse. The objective