Fractional CO 2Laser Resurfacing

Fractionated CO ₂lasers are a new treatment modality for skin resurfacing. These lasers have been shown efficacious in treating facial photoaging changes and scars. These lasers have an improved safety and recovery profile compared with traditional CO ₂laser resurfacing. Precise treatment parameters vary between patients, the pathology treated, and the details of the particular laser.

The advent of lasers in the 1960s led to a paradigm shift in skin rejuvenation. The carbon dioxide (CO ₂ ) laser was designed at Bell Laboratories (Murray Hill, NJ, USA) by Patel in 1964. Medical applications of CO ₂ lasers started in the latter 1970s. These lasers were found to provide significant advantages when dealing with pediatric airway problems. In 1993, using high-energy CO ₂ lasers, the first skin resurfacing was performed. By 1998 they had become popularized for skin rejuvenation; however, by that time it also had become apparent that there were risks of significant complications.

The CO ₂ laser emits an invisible infrared beam at a 10,600-nm wavelength, which is strongly absorbed by the chromophore, water (absorption coefficient, 800 cm ⁻¹ ). Light energy from the CO ₂ laser is absorbed by intracellular and extracellular water, resulting in coagulative necrosis and skin vaporization. A single pulse of the CO ₂ laser with fluences of 4 J/cm ² to 19 J/cm ² ablates 20 μm to 40 μm depth of skin. The depth of penetration can be changed by altering the laser fluence and/or pulse duration. Altering these also affects the surrounding zone of thermal injury.

The high-energy pulsed resurfacing CO ₂ laser utilizes the laser biophysics concept of thermal relaxation time (TRT). This is the time required for the target tissue to lose 50% of its heat to surrounding tissue. The TRT for 20 μm to 30 μm of skin is approximately 1 ms. Selective heating of the target chromophore, water, is achieved when utilizing a laser pulse duration time shorter than the TRT. With pulse duration of less than 1 ms and an energy fluence of 4 J/cm ² to 19 J/cm ² , the pulsed CO ₂ laser selectively vaporizes 20 μm to 40 μm of tissue.

The high-energy pulsed resurfacing CO ₂ laser is the gold standard for modern ablative laser therapy. There also was a second basic type of CO ₂ laser, which used a computer-controlled optomechanical flash scanner for resurfacing. This device, the FeatherTouch/SilkTouch (Sharplan Lasers, Allendale, NJ, USA) is of historical interest only because Sharplan was acquired by Lumenis (Palo Alto, CA, USA) and these lasers are no longer manufactured; it used a rapid scan with a focal spot of a continuous wave CO ₂ laser over the skin, with a dwell time of less than 1 ms.

Resurfacing CO ₂ lasers have been effective in the treatment of facial rhytides and scarring. Most reports found significant, 50% to 90%, improvement. Studies also reported improvement in scars. Although ablative high-energy pulsed CO ₂ laser therapy has been shown effective, there is a risk of associated complications. These include infection, persistent or prolonged erythema, delayed hypopigmentation, hypertrophic scars, ectropion, and scleral show. Over time, considering the possibility of postresurfacing prolonged erythema and the risks of complications, other lasers were developed. These included nonablative lasers, fractional nonablative lasers, and, most recently, fractional ablative lasers.

Fractional photothermolysis

The first laser to use fractional photothermolysis was nonablative. All fractional lasers create spaced columns of treated tissue rather than treating an entire area. Between these treated columns the tissues are not lasered; however, these unlasered adjacent tissues are subject to bulk heating effects. The first fractional device was a 1550-nm laser, the Fraxel SR (Solta Medical, Hayward, CA, USA).

Subsequently, ablative fractional lasers were created. In contrast to the nonablative fractional lasers, these devices vaporize columns of epidermis and part of the dermis as well as producing adjacent tissue heating. As with the nonablative fractional lasers, there is viable epidermis and dermis in the adjacent untreated areas. The percentage of the area that is vaporized varies, depending on the parameters that are set by the laser surgeon.

Initial healing after ablative fractional resurfacing occurs by more than one mechanism. Keratinocyte migration from the adjacent tissue into ablated areas occurs within the first 24 to 48 hours. This rapid epithelialization is associated with the decreased risk of infection, erythema, and scarring as well as a faster recovery time. Furthermore, there are the beneficial effects of the adjacent fibroblasts and stem cells. This results in wound remodeling with neocollagenesis and elastic fibrin formation with subsequent skin tightening and improved appearance.

Currently, there are several fractionated CO ₂lasers available. These include Fraxel re:pair, Juvia, Affirm CO ₂, Active FX, Deep FX, Pixel CO ₂OMNIFIT, MiXto SX, and Matrix. Different fractional CO ₂lasers can vary in treatment spot diameter, pulse energy, and treatment depth. There is controversy as to whether a particular fractionated laser is more effective than the others. In one study, with limited follow-up, there was no significant difference in outcome between the lasers that were evaluated.

For any one fractionated CO ₂laser, an increase in fluence increases penetration depth. Increasing pulse duration increases adjacent nonlasered tissue heating effects. Increasing microspot density increases the percentage of treated area. The issue of optimal depth of penetration for this procedure is controversial. In general, the first author (PJC) prefers a smaller microspot size, shorter pulse duration, and higher fluence. One study found that the time for reepithelialization was the same in patients treated with superficial fractional and in those treated with deep fractional CO ₂laser resurfacing.

Indications for fractional CO ₂laser

Currently, fractional CO ₂lasers are used for treatment of photoaging (rhytides, dyschromia, lentigines, and skin laxity) ( Fig. 1 ) and scarring (acne, traumatic, and surgical). Significant improvement has been reported for treatment of periorbital/perioral fine rhytides. These facial skin aging changes are less amenable to improvements with rhytidectomy. Fractional CO ₂laser resurfacing is effective for treatment of facial fine-moderate rhytides and static wrinkles. Dynamic rhytides have less predictable results and can be combined with neurotoxins for treatment of the dynamic component to optimize the results. There are varying reports on the use of fractional CO ₂lasers for the cervical region. In one limited study, there were no significant problems with fractional laser resurfacing of the neck. In contrast, another retrospective study reported on significant scarring.

Indications for fractional CO ₂laser

Currently, fractional CO ₂lasers are used for treatment of photoaging (rhytides, dyschromia, lentigines, and skin laxity) ( Fig. 1 ) and scarring (acne, traumatic, and surgical). Significant improvement has been reported for treatment of periorbital/perioral fine rhytides. These facial skin aging changes are less amenable to improvements with rhytidectomy. Fractional CO ₂laser resurfacing is effective for treatment of facial fine-moderate rhytides and static wrinkles. Dynamic rhytides have less predictable results and can be combined with neurotoxins for treatment of the dynamic component to optimize the results. There are varying reports on the use of fractional CO ₂lasers for the cervical region. In one limited study, there were no significant problems with fractional laser resurfacing of the neck. In contrast, another retrospective study reported on significant scarring.