AUTHOR=Xia Fei , Qin Bing , Shang Jianmin , Chen Zhuoyi , Zhou Xueyi , Zhao Jing , Wang Xiaoying , Zhou Xingtao 

TITLE=Four-Year Outcomes of Small Incision Lenticule Extraction for Extreme High Myopia and Myopic Astigmatism

JOURNAL=Frontiers in Medicine

VOLUME=Volume 7 - 2020

YEAR=2020

URL=https://www.frontiersin.org/journals/medicine/articles/10.3389/fmed.2020.575779

DOI=10.3389/fmed.2020.575779

ISSN=2296-858X

ABSTRACT=Purpose: To evaluate the long-term safety, efficacy, predictability, and stability of small incision lenticule extraction (SMILE) for the treatment of high myopia and myopic astigmatism greater than -10.0 D.
Methods: This was a prospective study that incorporated 35 consecutive patients (35 eyes) undergoing SMILE from September 2015 to March 2016. These patients had a mean preoperative spherical equivalent refraction of -10.06±0.64 D. Patients were followed over a four-year period and assessed for outcomes including uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), manifest refraction, and corneal topography. 
Results: At four years post-SMILE, respective efficacy and safety indices were 1.01±0.19 and 1.07±0.15. In total, 97% of operated eyes achieved an UDVA of 20/25 or better. ≥ 1 line was gained for 9 eyes (26%), with 25 eyes (71%) remained stable. 24 (69%) and 33 (94%) eyes, respectively, were within ± 0.50 D and ± 1.0 D of target refraction. From three months to four years postoperatively, a mean refractive regression of -0.22 D (-0.06 D per year) was detected, whereas no significant changes in mean corneal back curvature or posterior central elevation were detected (P=0.617 and 0.754, respectively). We detected significant increases in higher-order aberrations (HOAs) of the anterior and total cornea (all P<0.001), with spherical aberrations and vertical coma being particularly common, whereas posterior corneal HOA remained fairly stable (all P<0.05).
Conclusion: SMILE is a safe, effective, predicable and stable means of correcting high myopia and myopic astigmatism over a four-year postoperative period.