Depth of eCO 2 Fractional Resurfacing with 3 Different Spot Sizes on Facial Skin in vivo

Abstract

Introduction:

To estimate the depth of laser vaporization of microthermal zones and surrounding thermocoagulation with the eCO₂ laser.

Materials and Methods:

Pretragal skin was lased with 3 spot sizes (120, 300, and 1000 μm), and each spot size was lased at 5 different fluences. The 15 different lased areas were then biopsied.

Results:

For the 120-μm tip, as the power increases from 80 to 160 mJ, the depth of laser penetration increased from 520 to 900 μm. Total coagulative effect increased from 720 to 1000 μm. For the 300-μm tip, as the power increases from 100 to 180 mJ, the depth of laser penetration increased from 200 to 550 μm. Total coagulative effect increased from 320 to 720 μm. For the 1-mm tip, as power increased from 60 to 220 mJ, the depth of laser penetration hovered around 125 to 150 μm. Total coagulative effect increased from 150 to 350 μm.

Conclusion:

The 120-μm tip allows for the deepest penetration into facial skin with the least amount of surface area ablated. The 300-μm tip allows for an intermediate level of penetration into the dermis and an intermediate amount of surface ablation. The 1000-μm tip can be used to fully ablate epidermis as in traditional laser resurfacing. Traditional CO₂ lasers ablate the entire epidermis, which provides excellent results at the price of prolonged healing times and erythema. These lasers worked with larger spot sizes, often as much as 2.25 mm, and at fluences of about 7–8 J/cm². Fractional CO₂ lasers focus the same amount of energy into the skin in microscopic thermal zones as small as 120 μm, which create fluences of nearly 100 times those of traditional lasers. This results in tissue ablation past the epidermis and through the papillary dermis into the reticular dermis in these narrow zones while leaving the surrounding epidermis intact. These areas of undisturbed tissue allow for more rapid healing. The theory is that the deep penetration into the reticular dermis allows for deep collagen neogenesis, which is good for rhytid improvement while maintaining a rapid healing time.