Dynamic corneal parameter changes and safety in patients with moderate to high risk of corneal ectasia 12 months after SMILE Xtra surgery

Authors:Miao Zhuang, Mo Jing, Lu Qi, Li Qinglan

Corresponding author: Mo Jing, Email:mojing@aierchina.com

Published:2026-08-10

DOI:10.3760/cma.j.cn115989-20250423-00132

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ABSTRACT 

Objective To analyze the dynamic changes of multiple corneal parameters and the safety of femtosecond laser small-incision lenticule extraction combined with corneal cross-linking (SMILE Xtra) 12 months postoperatively in patients with moderate-to-high risk of corneal ectasia.

Methods A prospective self-control study was conducted. A total of 31 myopic patients (54 eyes) who underwent SMILE Xtra at Aier Eye Hospital (East of Chengdu) from May 2023 to February 2024 were enrolled. All patients were classified as moderate to high risk according to the Randleman Ectasia Risk Score System (ERSS). Uncorrected distance visual acuity (UDVA), manifest refraction spherical equivalent (MRSE), intraocular pressure (IOP), maximum keratometry (Kmax), mean keratometry (Kmean), corneal morphological indices including central keratoconus index (CKI), index of highest decentration (IHD), index of surface variance (ISV), and index of vertical asymmetry (IVA), corneal biomechanical parameters including stiffness parameter at first applanation (SP-A1), stress strain index (SSI), and integrated radius (IR), corneal densitometry (CD) were recorded preoperatively and at 1, 3, 6, and 12 months postoperatively, and complications were also recorded. This study followed the Declaration of Helsinki. The study protocol was approved by the Ethics Committee of Aier Eye Hospital (East of Chengdu) (No. DQAIER202303001). All patients signed the informed consent form.

Results UDVA, absolute value of MRSE, Kmax, Kmean, IOP, CKI, and SP-A1 at different postoperative time points were significantly decreased compared with preoperative, while IHD, IVA, and IR were significantly increased (all P<0.005). SP-A1 at 3, 6, and 12 months postoperatively was higher than that at 1 month postoperatively, SSI at 1, 6, and 12 months postoperatively was significantly decreased compared with preoperative, SSI at 3 months postoperatively was higher than that at 1, 6, and 12 months postoperatively, and IR at 3 months was significantly decreased compared with that at 1 month postoperatively (all P<0.005). There were no statistically significant differences in pairwise comparisons of UDVA, MRSE, Kmax, Kmean, IOP, CKI, IHD, and IVA at any postoperative time points (all P>0.005). No statistically significant difference was found in ISV across different time points ( χ ²=4.75, P=0.314). Preoperative and postoperative CD at 1, 3, 6, and 12 months were (16.92±1.28), (17.89±1.76), (17.83±1.80), (17.45±1.90), and (17.30±1.70) grayscale units ( GSU), respectively, with a statistically significant overall difference ( F=9.57, P<0.001). Specifically, CD at 1 and 3 months postoperatively was significantly increased compared with preoperative (both P<0.001); CD at 6 and 12 months after surgery recovered to preoperative baseline level, with no statistically significant differences (both P>0.005). At 1 month postoperatively, grade 0.5 haze was observed in 4 eyes (7.4%) and grade 1 haze in 9 eyes (16.7%); at 3 months postoperatively, grade 0.5 haze was observed in 8 eyes (14.8%) and grade 1 haze in 3 eyes (5.6%). All haze resolved within 6 months after treatment.

Conclusions SMILE Xtra demonstrates favorable efficacy, stability, and safety in correcting ametropia among patients with moderate to high risk ERSS within 12 months postoperatively. Corneal biomechanical properties at 3 months postoperatively were enhanced compared with those at 1 month postoperatively. Nevertheless, SSI variability and haze occurrence postoperatively demand clinical attention.

KEYWORDS：

Myopia;Small incision lenticule extraction;Corneal cross-linking;Corneal biomechanics;Corneal morphology;Corneal densitometry

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Authors Info & Affiliations 

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