What Are the Histological Changes Corresponding to Clinical Effacement of Atrophic Acne Scars After Fractional Carbon Dioxide Laser Intervention-A Prospective Interventional Study in Skin of Color.

BACKGROUND

Pre-defined dose parameters of fractional carbon dioxide (Fr:CO2) laser used for acne scars are not aligned with the histological depth achieved by the laser, which predicts scar improvement.

OBJECTIVES

To evaluate the baseline histological depth and architecture of different acne scars and compare the histological changes and clinical improvement after Fr:CO2 laser.

METHODS

We conducted a prospective study of atrophic acne scars-ice-pick, boxcar, or rolling. The patients were treated with three sessions of Fr:CO2 laser with pre-determined dosimetry at 3-month intervals. Clinical evaluation was done at every visit using Echelle d'Evaluation clinique des Cicatrices d'acné (ECCA) scoring and individual atrophic acne scars count. Punch biopsy of predominant scars was taken pre- and 1-month post-treatment. The vertical depth of the scars was measured and histological changes in collagen and elastin were noted.

RESULTS

Forty-three patients with atrophic acne scars were included (27 boxcar, 9 ice-pick, and 7 rolling). Median histological depth of ice-pick, rolling and boxcar scars in pre-laser biopsies was 1606, 1546 and 1172 μm respectively, which significantly reduced to 1024 (p = 0.008), 858 (p = 0.018) and 746.5 μm (p < 0.0001) after the final laser session. Significant correlations were noted between acne scar reduction efficiency (ASRE%) and histological parameters at 7 months [ASRE% boxcar, increase in collagen grading (p < 0.05); ASRE% rolling, increased scar vascularization (p = 0.03) and ASRE% ice-pick, increased surrounding dermal elastin (p ≤ 0.05)].

CONCLUSION

Fr:CO2 laser intervention should be guided by scar-specific depth assessment, enabling optimal dosing and correlating this with histological changes would determine clinical improvement in acne scars.