Measurement of Lenticular Decentration with the Coaxial Subject-Fixation Alignment Method in SMILE and Its Impact on Visual Quality
Shulin Wang, Chenjiu Pang, Bo Zhang, Shengwei Ren, Yuwei Gu, Lijuan Dai
Henan Provincial People's Hospital, Henan Eye Institute, Henan Eye Hospital, Henan Key Laboratory of Ophthalmology and Visual Science, People's Hospital of Zhengzhou University, School of Medicine Henan University, Zhengzhou 450003, China
Abstract：Objective:To measure lenticular decentration with the coaxial subject-fixation alignment method after femtosecond laser small incision lenticule extraction (SMILE), and to investigate its impact on visual quality. Methods:A total of 37 patients (74 eyes) with myopia and myopic astigmatism who underwent the SMILE procedure using the coaxial subject-fixation alignment method were included in the prospective study from August to October 2017 in Henan Provincial People's Hospital. Visual acuity, refraction, corneal topography and objective visual quality were measured. The Cartesian coordinate was established with the pupil center as the origin of the coordinate. Lenticular decentration was measured and calculated according to the offset value of the corneal topography and the video capture of the SMILE procedure. Patients were divided into groups based on lenticular decentration: group A (<200 μm), group B (200-300 μm) and group C (>300 μm). The modulation transfer function cutoff (MTF cutoff) was used to evaluate objective visual quality. Pre-op and post-op indexes were compared with a paired t-test and ANOVA, and the correlation of factors affecting the correction of astigmatism was analyzed by Spearman correlation. Results:Lenticular decentration was 223±108 μm and all treated eyes (100%) were within 500 (9-464)μm: group A (<200 μm) consisted of 32 eyes (43%), group B (200-300 μm) consisted of 26 eyes (35%), and group C (>300 μm) consisted of 16 eyes (22%). The mean value of the MTF cutoff preoperatively was 39.6±5.2 circle/degree (c/d), of which group A was 39.7±5.8 c/d, group B was 39.0±5.2 c/d, and group C was 40.2±3.9 c/d. The mean value of the MTF cutoff was 38.6±5.8 c/d one month after surgery: group A was 37.8±5.9 c/d, group B was 38.8±6.6 c/d, group C was 40.6±3.8 c/d, and there was no statistically significant difference among groups and between preoperation and 1 month postoperation in group C. There was a significant relationship between the MTF cutoff before and one month after the surgery (r=0.53, P<0.001). The vector distance that the lenticular center deviated from the pupil center was 209±104 μm, which was found to be associated with lenticular decentration (r=0.49, P<0.001). Conclusions:Although the coaxial subject-fixation alignment method in SMILE can cause slight lenticular decentration, it has no significant impact on visual quality after surgery.
王树林, 庞辰久, 张波, 任胜卫, 顾宇伟, 代丽娟. 共轴注视定位法测量SMILE术透镜偏心值及偏心对视觉质量的影响[J]. 中华眼视光学与视觉科学杂志, 2018, 20(11): 653-658.
Shulin Wang, Chenjiu Pang, Bo Zhang, Shengwei Ren, Yuwei Gu, Lijuan Dai. Measurement of Lenticular Decentration with the Coaxial Subject-Fixation Alignment Method in SMILE and Its Impact on Visual Quality. Chinese Journal of Optometry Ophthalmology and Visual science, 2018, 20(11): 653-658.
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