Scheimpflug analysis of corneal power changes after hyperopic small incision lenticule extraction

Dan Fu,Xiaoyu Zhang,Tian Han,Jianmin Shang,Xingtao Zhou,Lingling Niu

doi:10.1186/s12886-021-02043-w

Abstract

PurposeTo assess the ability of the Pentacam in predicting the corneal power after hyperopic small-incision lenticule extraction (SMILE).MethodsTwenty-five eyes of 22 patients underwent hyperopic SMILE were prospectively followed. All patients finished at least 6 months visit. Cornea power was obtained by Pentacam HR, in the format of mean keratometry (Km), equivalent keratometry (EKR) and total cornea refractive power (TCRP). Calculation of TCRP were centered on either the corneal apex or the pupil center within a ring or zone, giving a total of four different subtypes naming AR、AZ、PR、PZ. Clinical history method (CHM) was regarded as a gold standard and was compared with other cornea power parameters.ResultsCenter difference had no impact on the TCRP values (PR vs AR and PZ vs AZ, P > 0.05). Compared with CHM, no difference was found in Km, EKR 4.0 mm, EKR 4.5 mm, PR 3.0 mm, PR 4.0 mm, AR 3.0 mm and AR 4.0 mm. PR 4.0 mm showed the least difference with CHM (− 0.14 ± 1.03D, P > 0.05). The 95% limit of agreement (LOA) of the TCRPs and CHM was not close. The top two were PR 3.0 mm and PR 4.0 mm, LOA of which were − 2.20 to 1.84 D and − 2.18 to 1.68 D respectively. Central cornea thickness was correlated with error (TCRP – CHM) of PR 4.0 mm (r = 0.58, P = 0.003).ConclusionsThe Pentacam topographer is an alternative method of measuring corneal power in eyes after hyperopic SMILE. The optimal options seem to be the TCRP (PR 4.0 mm). The agreement needs more verifications.

Highlights

Cornea refractive surgery is getting wide acceptance by surgeons and patients around the world
Promising results of the ray tracing have been reported in eyes after myopic photorefractive keratectomy (PRK), laser in situ keratomileusis (LASIK), and small incision lenticule extraction (SMILE) [9,10,11,12,13]
This study aims to assess the ability of the Pentacam in predicting the corneal power in eyes after hyperopic SMILE

Summary

Introduction

Cornea refractive surgery is getting wide acceptance by surgeons and patients around the world. Promising results of the ray tracing have been reported in eyes after myopic photorefractive keratectomy (PRK), laser in situ keratomileusis (LASIK), and small incision lenticule extraction (SMILE) [9,10,11,12,13]. There are a few studies about cornea power change after hyperopic surgery, and most of them focused on hyperopic LASIK [11, 14,15,16,17]. Hyperopic LASIK used excimer laser to ablate midperiphery cornea area. Compared with LASIK, hyperopic SMILE is a relative young cornea surgery, by creating a convex lens using femtosecond laser. Reinstein et al have reported the promising refractive results of hyperopic SMILE [18]. In terms of cornea power prediction, it seems no published study exists

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