Effect of Cyclotorsion Compensation With a Novel Technique in Small Incision Lenticule Extraction Surgery for the Correction of Myopic Astigmatism

Abstract

PURPOSE: To comparatively investigate the clinical outcomes of small incision lenticule extraction (SMILE) surgery with or without cyclotorsion compensation for the correction of myopic astigmatism. METHODS: This prospective, double-blinded, randomized controlled trial included patients who underwent SMILE surgery with bilateral myopic astigmatism. Two eyes of a single patient were randomly divided into the static cyclotorsion compensation (SCC) group and the control group. In the SCC group, the intraoperative cyclotorsion was manually compensated with a novel technique. In the control group, the cyclotorsion was not compensated. Visual acuity, manifest refraction, aberrations, objective visual quality, and contrast sensitivity were measured preoperatively and postoperatively. RESULTS: A total of 132 eyes from 66 patients were analyzed at the 3-month follow-up. The mean preoperative cylinder values in the SCC and control groups were −1.52 ± 0.81 and −1.57 ± 0.82 diopters (D), respectively. The mean cyclotorsion during surgery was 0.60° ± 0.63° (range: 0° to 3.2°) in the SCC group and 3.21° ± 2.33° (range: 0.1° to 10.8°) in the control group ( P < .001). Both groups showed favorable results in the correction of myopic astigmatism. No statistically significant difference was found between the two groups in visual and refractive outcomes, vector parameters, entire eye aberrations, objective visual quality, or contrast sensitivity. No significant benefit was gained from cyclotorsion compensation, even in the high astigmatism subgroup. CONCLUSIONS: The cyclotorsion compensation technique used in this study helped minimize the alignment error but was not compulsory because the ocular rotation in SMILE surgery using a well-controlled position was too small to affect the astigmatic outcomes or postoperative visual quality. [ J Refract Surg . 2019;35(5):301–308.]

Simple method of measuring ocular rotation in supine position during small incision lenticule extraction

“…Recently, studies on the results of manual compensation in SMILE have been published [8][9][10][11] . Chen et al [10] reported that 84 patients were treated with standard SMILE for 30 patients and SMILE with manual cyclotorsion compensation for 54 patients.…”

“…The SE of the two groups was the same, but better results were obtained in the vector analysis of astigmatism. Xu et al [8] compared the surgical results of the group with and without manual compensation in SMILE and found no difference between the two groups in terms of visual acuity and refractive outcomes, even in high astigmatism. According to this result, Xu et al [8] reported that manual compensation could reduce alignment error, but the average amount of cyclotorsion was too small to affect astigmatism, so it was not compulsory.…”

“…Xu et al [8] compared the surgical results of the group with and without manual compensation in SMILE and found no difference between the two groups in terms of visual acuity and refractive outcomes, even in high astigmatism. According to this result, Xu et al [8] reported that manual compensation could reduce alignment error, but the average amount of cyclotorsion was too small to affect astigmatism, so it was not compulsory. Köse [9] proposed a method of compensating cyclotorsion by overlapping an image taken in an upright state on a surgical screen using an image-guided system and rotating the patient's head.…”

“…Therefore, errors may occur in centering and in the accurate setting of the astigmatism axis during surgery. There are several studies on how to correct these errors; however, all these techniques are manual methods [8][9][10][11] . There have been several studies in measuring static cyclotorsion, and among them, Jackson cross cylinder [12] , Maddox double-rod test [13] , videokeratography [14] , and intraoperative measurement were used [2][3][4][5] .…”

<p>Initial Single-Site Experience Using SMILE for the Treatment of Astigmatism in Myopic Eyes and Comparison of Astigmatic Outcomes with Existing Literature</p>

“…5,6 In 2018, the US FDA approved SMILE for the treatment of myopic astigmatism from >−0.50 to ≤−3.00 diopters (D), 7 and the use of SMILE for this indication has since been further investigated. [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] Previous studies on the treatment of astigmatism with SMILE have found that it is safe and effective, but these studies were conducted outside of the United States. Our study will assess a single site's initial experience with SMILE for the treatment of myopic astigmatism and compare outcomes with FDA results and published literature.…”