Effect of preoperative keratometry on visual outcomes after small-incision lenticule extraction for myopia

Seongjun Lee,Sinwoo Bae,Moonsun Jung

doi:10.1007/s10792-021-02167-4

Seongjun Lee, Sinwoo Bae + Show 1 more

Open Access

https://doi.org/10.1007/s10792-021-02167-4

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Abstract

PurposeTo investigate the relationship between preoperative keratometry (K) and postoperative refraction and compare the visual outcomes after small-incision lenticule extraction (SMILE) between preoperative flat and steep corneas.MethodsThis study involved 814 consecutive eyes of 409 patients who underwent SMILE. A month later, a linear regression analysis of the relationship between preoperative K and the residual spherical equivalent (SE) along with eyes divided by a single standard deviation between flat and steep corneas (< 41.85 D, > 44.57 D, respectively) was conducted. Eyes were distinguished based on the degree of myopia.ResultsOne month after surgery, no significant correlation existed between mean preoperative K and residual SE (P = 0.459). Linear regression analysis showed a weak negative correlation between flat corneas (r2 = 0.042, P = 0.025) rather than steep corneas (P = 0.908). Eyes with preoperative low myopia (< 3.00 D) (r2 = 0.233, P = 0.001) had a weak correlation compared with moderate and high myopia (P = 0.272, P = 0.257, respectively). Twelve months later, the predictability, safety, and efficacy did not vary between preoperative flat and steep corneas (P > 0.05).ConclusionsOne month after SMILE for myopia, the corneas were flatter in the preoperative flat corneas or all the low myopic corneas, and they were more overcorrected. However, preoperative corneal curvature does not influence visual outcomes at 1 year after SMILE.

Highlights

Even though small-incision lenticule extraction (SMILE) is a safe, efficient, and predictable surgical method for correction of myopia, the predictability of the technique as well as laser in situ keratomileusis (LASIK) and surface ablation is disputed, especially in eyes with high degrees of myopia or hyperopia [1,2,3,4,5,6,7,8,9]
Previous studies showed no relationship between preoperative corneal curvature and postoperative predictability after myopic laser-assisted subepithelial keratectomy (LASEK) [14]; when treating preoperative higher myopia in steeper corneas, a weak tendency existed toward overcorrection [12]
The present study investigated the relationship between preoperative keratometry and postoperative refraction and compared the visual outcomes between eyes with preoperative flat and steep keratometric (K) readings for 12 months after SMILE

Summary

Introduction

Even though small-incision lenticule extraction (SMILE) is a safe, efficient, and predictable surgical method for correction of myopia, the predictability of the technique as well as laser in situ keratomileusis (LASIK) and surface ablation is disputed, especially in eyes with high degrees of myopia or hyperopia [1,2,3,4,5,6,7,8,9]. A few studies have evaluated the effect of preoperative keratometry on visual outcomes after LASIK or surface ablation and predictors of SMILE outcomes [10,11,12,13]. In previous studies evaluating the effect of preoperative keratometry (K) on visual outcomes after LASIK for myopia, eyes with flatter corneas tended to have greater undercorrection than eyes with similar myopia and steeper corneas, and undercorrection and loss of best spectacle-corrected visual acuity following hyperopic LASIK in eyes with steep corneas [10, 11]. Moderately myopic eyes with flatter corneas preoperatively show better visual prognosis following LASIK compared with steeper corneas [15]. The extent of epithelial injury plays a critical role and determines the stromal response after LASIK or photorefractive keratectomy (PRK) [16]. Predictability after SMILE differs from that of LASIK and PRK

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