Clinical Outcomes of Small Incision Lenticule Extraction in Myopia: Study of Vector Parameters and Corneal Aberrations

Abstract

Since Jose Barraquer invented keratomileusis for correction of high myopia in 1949, researchers have combined keratomileusis with excimer laser surface ablation to develop one of the most commonly used laser corneal refractive surgery techniques, laser in situ keratomileusis (LASIK) [1]. Creation of a corneal flap allows early visual recovery, less discomfort, and reduced stromal inflamma-Purpose: To investigate clinical outcomes of small incision lenticule extraction (SMILE) including vector parameters and corneal aberrations in myopic patients. Methods: This retrospective, observational case series included 57 eyes (29 patients) that received treatment for myopia using SMILE. Visual acuity measurement, manifest refraction, slit-lamp examination, autokeratometry, corneal topography, and evaluation of corneal wavefront aberration were performed preoperatively and at 1 and 3 months after surgery. We analyzed the safety, efficacy, vector parameters, and corneal aberrations at 3 months after surgery. Results: Preoperatively, mean manifest refraction spherical equivalent refraction was -4.94 ± 1.94 D (range, -8.25 to 0 diopters [D]), and the cylinder was -1.14 ± 0.82 D (range, -3 to 0 D). Mean manifest refraction spherical equivalent improved to -0.10 ± 0.23 D at 3 months postoperatively, when uncorrected distance visual acuity was 20 / 20 or better in 55 (96%) eyes. The linear regression model of target induced astigmatism vector versus surgically induced astigmatism vector exhibited slopes and coefficients (R 2 ) of 0.9618 and 0.9748, respectively (y = 0.9618x + 0.0006, R 2 = 0.9748). While total corneal root mean square higher order aberrations, coma and trefoil showed statistically significant increase, spherical aberration did not show statistically significant change after SMILE. Conclusions: SMILE has proven to be effective and safe for correcting myopia and astigmatism. We showed that SMILE did not induce spherical aberrations. A small increase in postoperative corneal higher order aberration may be associated with increase in coma and trefoil.

Vector analysis of moderate to high myopic astigmatism after small-incision lenticule extraction (SMILE): 12-month follow-up

“…However, both mentioned studies had lower preoperative SE and astigmatism compared to our study. 15,19 These results show that the SMILE procedure achieves good outcomes in the correction of myopia, although greater preoperative astigmatism results in higher SE outcomes. In terms of stability, a 10-year follow-up study of SMILE reported a regression of 0.30 D in SE.…”

“…These results are in accordance with the results of previous studies. 12,15,19 Vector analysis demonstrates that the proportional loss of the flattening effect is 1.5% when treatment is misaligned by 5 degrees and as high as 50% when 30 degrees. 26 Therefore, the astigmatic magnitude and treatment alignment both affect the outcomes of astigmatism correction.…”

Small-incision lenticule extraction in the U.S. military: prospective study of visual and military task performance

“…Studies have reported that despite increases in spherical aberrations, coma, trefoil, and total HOAs after SMILE, there is no clear association with visual symptoms. [25][26][27][28] Both LCVA and contrast sensitivity are important measures of quality of vision. Despite increases in HOAs, our study showed LCVA and contrast sensitivity may fluctuate in the early postoperative period after the SMILE procedure.…”

“…Studies have reported that despite increases in spherical aberrations, coma, trefoil, and total HOAs after SMILE, there is no clear association with visual symptoms. 25–28…”

<p>Initial Single-Site Experience Using SMILE for the Treatment of Astigmatism in Myopic Eyes and Comparison of Astigmatic Outcomes with Existing Literature</p>

“…5,6 In 2018, the US FDA approved SMILE for the treatment of myopic astigmatism from >−0.50 to ≤−3.00 diopters (D), 7 and the use of SMILE for this indication has since been further investigated. [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] Previous studies on the treatment of astigmatism with SMILE have found that it is safe and effective, but these studies were conducted outside of the United States. Our study will assess a single site's initial experience with SMILE for the treatment of myopic astigmatism and compare outcomes with FDA results and published literature.…”