Niels Lyhne

Letter of response: Small-incision lenticule extraction (SMILE): Outcomes of 722 eyes treated for myopia and myopic astigmatism

Dear Editor, We thank assistant Prof. Payman and Dr. Alemzadeh-Ansari for their letter in response to our publication. We are aware of the intraocular correlations, as mentioned in the limitations. The optimal way to address this issue is to use only one eye of each patient, or to use advanced statistical analyses, for example, mixed models in STATA to adjust for the cluster structure of data. However, this is not always the case in all publications, and, in one of the largest yet published cohorts of SMILE patients [1], it was found that correlations were low in eyes having undergone refractive surgery, and that results were similar when using one or two eyes of the patients. This is, of course, not the case if data are based on outcome measurements in patients with a systemic disease such as diabetes, which would affect both eyes and increase correlations. We have followed the standard graphs and tables for reporting outcomes after refractive surgery at the time [2]. However, we agree that astigmatic vector analysis could be an effective additional tool when analyzing astigmatic treatment efficacy in refractive surgery. Concerning the ranges of preoperative cylinder as reported in Table 1, we agree that positive cylinders should not be given. The cylinder range of −3.0 to 1.0 D was based on an unfortunate typographical error. The correct range should be – 3.0 to 0.0 D of cylinder, since we only used a negative cylinder format in the article. We thank assistant Prof. Peyman and Dr. Alemzadeh-Ansari for pointing this out.