Abstract
Purpose :
Small incision lenticule extraction (SMILE) has been proven to be safe and effective method for the treating myopia and astigmatism. However, tendency toward undercorrection of astigmatism in SMILE has been a limitation in patients with high astigmatism. The aims of this study are to evaluate the refractive outcome of high astigmatism compared to low astigmatism treated with SMILE and to investigate factors influencing residual astigmatism after SMILE.
Methods :
This is a retrospective study including 1586 eyes from 793 patients (372 males and 429 females) who had SMILE from October 2020 to July 2021 at B&VIIT Eye Center, Seoul, South Korea. The eyes were divided into two groups according to the level of astigmatism of manifest refraction (MR), high astigmatism group (2D or more) and low astigmatism group (less than 2D). The refractive outcomes were analyzed 12 months after the surgery. A modified nomogram for treating astigmatism was adopted using augmentation by 110% of the magnitude of MR to avoid undercorrection. If corneal astigmatism was greater than 25% of MR, the nomogram for treating astigmatism increased by 120%. If astigmatism was either against-the-rule or oblique, astigmatism of MR was used and increment was not performed.
Results :
A total of 1448 low astigmatic eyes (-0.73±0.53D) and 138 high astigmatic eyes (-2.22±0.26D) were enrolled. 12 Months after surgery, the cylinder level was -0.25±0.23D and -0.37±0.30D for low and high astigmatism groups, respectively (p for difference<0.001). Uncorrected distance visual acuity for each groups were -0.06±0.06 logMAR and -0.03±0.08 logMAR (p=0.178). According to the linear regression analysis in the high astigmatism group, the higher level of residual astigmatism was associated with the thinner central corneal thickness (β=0.021; p=0.039) and higher corneal back surface astigmatism (β=4.089; p=0.044).
Conclusions :
In this large-scale study, SMILE was effective in treating refractive errors with good predictability in both low and high astigmatism groups. There were no significant differences in visual acuity at 12 months after SMILE. However, more notable residual astigmatism was observed in high astigmatism. We found that thin cornea and high corneal back surface astigmatism were associated with higher residual astigmatism after SMILE in high astigmatism.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.