The Effect of Femtosecond-Laser Cutting Parameters on the Results of Small-Incision Lenticule Extraction (SMILE)

To determine the effect of femtosecond-laser cutting parameters on small-incision lenticule extraction (SMILE) results by evaluating cap thickness, interface light scattering and visual and refractive outcomes.58 right eyes treated with SMILE using a programmed cap thickness of 130 µm were divided into two groups according to laser settings: group 1: 165 nJ pulse energy and 4.5 µm spot separation (n = 36); group 2: 125 nJ pulse energy and 4.2 µm spot separation (n = 22). The cap thickness was measured within the central 5 mm of the horizontal meridian using spectral-domain OCT. Postoperative interface light scattering was graded based on the percentage area showing light scattering: 0: no scattering; 1: ≤ 25%; 2: 26-50%; 3: 51-75%; and 4: > 75%.At 3 months postoperatively, cap thickness was 138.9 ± 6.2 µm in group 1 and 149.4 ± 3.5 µm in group 2 (p < 0.001). Interface scattering was 0.9 ± 1.0 in group 1 and 0.3 ± 0.9 in group 2 (p < 0.05), with no scattering in 33.3% and 86.4% eyes, respectively. The postoperative spherical equivalent refraction was -0.03 ± 0.44 D in group 1 and -0.04 ± 0.31 D in group 2. In group 1, 83.3% of the eyes were within ± 0.5 D of the desired outcome, and 69.4% achieved an uncorrected distance visual acuity of 20/20 or better. In group 2, these values were 95.5% and 86.4%, respectively.Lower pulse energy with tighter spots appears to reduce interface light scattering and improve refractive outcomes, while also significantly increasing cap thickness.