Modified Technique for Small-Incision Lenticule Extraction: Ye's Swing Technique

Abstract

Introduction: This study aimed to evaluate the lenticule integrity and refractive outcomes of a new technique, Ye's swing technique, during small-incision lenticule extraction (SMILE).

Methods: This prospective study enrolled patients who underwent the SMILE procedure using a modified technique for lenticule dissection. Per the standard SMILE procedure, the cap cut was opened using a hook, and an anterior dissection was performed with a counterclockwise swing, from 8 to 12 o'clock. A posterior dissection was then performed by swinging counterclockwise, leaving a thin band of the peripheral rim undissected, from 8 to 4 o'clock. The counterclockwise swing was continued to separate the edges of the rim from 4 to 12 o'clock, after which microforceps were used to extract the lenticules. The primary outcome measures were safety and lenticule integrity at the end of the surgery, and the secondary outcome measure was efficacy. Changes in the ocular parameters from the preoperative visit to 1 month postoperative, including uncorrected and corrected distance visual acuity, manifest refraction, lenticule quality, and lenticule residual, were assessed using optical coherence tomography.

Results: A total of 246 patients (490 eyes) with myopia and myopic astigmatism were included in the present study. The dissected lenticules ranged in size from 52 to 148 µm. Postoperatively, the lenticule was completely and successfully extracted in all cases. There was no incisional edge tearing during lenticule separation.

Conclusions: Ye's swing technique is a safe and effective procedure for lenticule dissection and refractive outcomes. We have now adopted this technique as our routine method for performing the SMILE procedure.

Keywords: Intraoperative complications; Lenticule tear; Myopia; SMILE; Small-incision lenticule extraction; Swing technique.

Fig. 1

Schematic of the spatula separating the lenticule. A The cap cut was along its entire length from left to right, while the lenticule cut was dissected along half its length from right to left by a small surgical hook; B, C the anterior dissection was performed counterclockwise from point a to point d with a swing by a blunt spatula, keeping the rest undissected to prevent lenticular movement; D, E the spatula was used to enter the cleavage plane on the posterior side of the lenticule to perform the partial swing counterclockwise from point a to point c counterclockwise, leaving a thin undissected band of peripheral rim; F, G the swing was continued towards point d over the margin; H the microforceps were used to grasp the free end of the lenticule, push it towards the center of the cornea, and peel it off gently clockwise in a continuous, circumferential motion; and I the anterior lenticule side was cut along the yellow dotted track, while the posterior cut moved along the red dotted track in the lenticule–stroma space. Points a, b, and d represent 8, 6, and 12 o’clock, respectively. The red dotted line represents the movement track of the spatula tip

Fig. 2

Visual outcomes of 406 eyes in 204 patients aged 18 to 35 years after small-incision lenticule extraction (SMILE). A Cumulative 1-week postoperative uncorrected distance visual acuity (UDVA) and preoperative corrected distance visual acuity (CDVA). B Changes in the Snellen lines of postoperative UDVA compared with preoperative CDVA. C Changes in the Snellen lines of postoperative CDVA compared with preoperative CDVA. D Attempted versus achieved changes in SER at 1 week after surgery. E Accuracy of the spherical equivalent refraction (SER) compared with the intended target. F Stability of the SER over 1 week. G Distribution of preoperative and 6-month postoperative cylinders. H Target-induced versus surgically induced astigmatism vectors at 1 week after surgery are shown. I Refractive astigmatism angle of error distribution is shown at 1 week after surgery. D diopters

Fig. 3

Anterior-segment domain optical coherence tomography image of the cornea after SMILE. A A left eye with a lenticule dissection of 52 µm. B A left eye with a lenticule dissection of 100 µm. C A right eye with a lenticule dissection of 143 µm

Fig. 4

An edge stress model based on Ye’s swing technique. A Three-dimensional (3D) shape based on the cut lenticle shape. B Calculated edge stress of point a by model. C Schematic of Ye’s swing technique