Nonablative Laser Treatments: A Review

Murad Alam, MD and his team evaluated histologic and tissue effects of nonablative laser therapy in a review of the literature published in Lasers in Surgery and Medicine. The data reviewed by the researchers was accessed via MEDline during the years 1995 to 2003 and from unpublished reports presented at major national meetings. The focus of the review was to better understand the clinical efficacy of nonablative treatments.

The type of devices reviewed included the KTP laser (with 1,064 nm Nd:YAG); pulsed-dye laser; intense pulsed light device; diode laser (980 nm); Nd:YAG laser (1,064 nm), Q-Switched; Nd:YAG laser (1,320 nm); diode laser (1,450 nm); Er:Glass laser; and the Er:YAG laser.

Most of the studies that evaluated these lasers included a subjective comparison of pre- and post-treatment histology using H&E or special stains. The post-treatment biopsies were usually obtained at a few time points. Most of the data was anecdotal making it difficult to substantiate many of the conclusions. 

The generalizations that can be drawn about tissue effects associated with nonablative laser treatment include:

1. Laser treatments that are used in combination with epidermal pre- or post-cooling can protect the epidermis from ablation, but it can also deliver a thermal injury to the dermis. The depth of the dermal injury may be increased if greater epidermal cooling is applied simultaneously.

2. Thermal injury to the dermis affects the vasculature, which causes a cascade of inflammatory events, including up-regulation of collagen expression and fibroblastic proliferation.

3. Collagen deposits are increased weeks to months after a series of nonablative treatments. The deposits assume a horizontal position parallel to the plane of the epidermis. Overall dermal and epidermal thickening has been reported.

4. Several different light and laser devices are able to induce similar histologic changes following nonablative resurfacing.

The major differences between ablative and nonablative laser treatments are detailed in the table below.

Ablative Laser	Nonablative Laser
Removes entire epidermis and portions of dermis	Epidermis not visibly disrupted
Improves skin roughness, fine periorificial lines, and dyspigmentation	Improves surface irregularities, skin texture, and wrinkles; some also address dyspigmentation, telangiectasia, and superficial erythema
Possible side effects: itching, erythema, edema, infection, scarring, hypo/hyperpigmentation	Possible side effects: mild erythema and edema
Healing time: 2-4 weeks	Healing time: several minutes to a few hours
1 treatment as needed every few years	5-6 treatments every 3-4 weeks

Previous research studies on the efficacy of nonablative laser treatments have been descriptive and emphasized phenomenology rather than assessing mechanisms of action. Clinical evaluations have previously relied on before and after photographs.  Additionally, the difficulty in comparing outcomes has been exacerbated by the various different laser and light settings and sources used for nonablative resurfacing. Fluence, pulse duration, number of passes, and cooling parameters vary across lasers, and even among the same devices.

Dr. Alam encouraged future researchers to impose a high degree of rigor and standardization to help overcome the small sample size. Using similar treatment methods, such as the same number of passes and same number of fluences would make the data more comparable and meaningful.

References

M. Alam, MD, et al. (2003). Nonablative laser and light treatments: Histology and tissue effects—A review. Lasers in Surgery and Medicine 33, 30-39.