INTRODUCTION
Procedural treatments for rhytides, photoaging, and acne
scars have ranged from aggressive and highly effective to
conservative with minimal efficacy. Traditional or standard
ablative laser skin resurfacing (LSR) with carbon dioxide (CO2) and
erbium-doped yttrium aluminum garnet (Er:YAG) lasers were highly
effective in reducing rhytides, photoaging, and acne scars but
were associated with significant side effects and complications.1
Dermabrasion and chemical peeling were also very effective, but
their side effects and complication rates were high.2,3 In an effort to
increase safety and decrease side effects and complications, nonablative
lasers and light-based devices, which neither ablate nor vaporize
tissue, were developed. Nonablative technologies targeted
chromophores in the epidermis and dermis and induced dermal
thermal injury without epidermal wounding.1 Although nonablative
modalities proved to be very safe, requiring no recovery time and
rarely causing side effects or complications, they provided low
or inconsistent efficacy, particularly in the reduction of rhytids.1
Fractional Laser Resurfacing
Most recently, a resolution of this therapeutic challenge was developed
with fractional LSR, which treated a fraction of the skin
surface with microscopic arrays of laser- or light-mediated effects
at higher dosages than nonablative LSR, but with intervening
zones of untreated skin for rapid recovery and excellent safety.4
By targeting microscopic spots of the skin with individual microbeams
of laser light, and sparing skin and stem cells in between,
rapid recovery and increased safety were achieved (Figure 1). Arrays
of microscopic columns of focal areas of energy-mediated
effects were created, such as to focally target a fraction of the
skin with many separate microbeams of laser or light.4 The microscopic
columns were termed microthermal treatment zones
(MTZs), extending from the epidermal layer into the dermis at
varying depths, and determined by several parameters, including
laser energy output and spot size.4 The categories of fractional
LSR included nonablative fractional LSR, which neither ablated
nor vaporized tissue, but caused microcolumns of thermal injury
in the dermis with a relatively intact superimposed epidermal
layer left in place. The second category was the ablative type,
which ablated or vaporized microcolumns of epidermis and dermis.
Of the 2 types of fractional lasers, nonablative and ablative,
the latter yielded higher efficacy with a small sacrifice in safety.
Fractional Nonablative Resurfacing
Technologic Properties
The first fractional laser was the nonablative 1,550-nm Er-doped fiber laser delivering 2,000 MTZs per cm2 (Fraxel, Solta, Hayward, CA; formerly Reliant Technologies).4 Microscopic laser spots were scanned across the skin through an optical scanner that laid down an array onto the skin. As the first attempt at implementing the fractional concept, the new technology, while clever, was cumbersome. It used an optical scanner that originally required the application of a blue dye to the patient's skin to facilitate tracking. Even with the application of topical anesthesia and the use of cool air, many found it unreasonably uncomfortable (Figure 2).
The first fractional laser was the nonablative 1,550-nm Er-doped fiber laser delivering 2,000 MTZs per cm2 (Fraxel, Solta, Hayward, CA; formerly Reliant Technologies).4 Microscopic laser spots were scanned across the skin through an optical scanner that laid down an array onto the skin. As the first attempt at implementing the fractional concept, the new technology, while clever, was cumbersome. It used an optical scanner that originally required the application of a blue dye to the patient's skin to facilitate tracking. Even with the application of topical anesthesia and the use of cool air, many found it unreasonably uncomfortable (Figure 2).
