The published study by Conart and colleagues is described as a nested case-control study; however, this is incorrect.1 Participants were selected based on the presence or absence of high myopia and were matched with respect to time of surgery, duration of symptoms, and preoperative visual acuity. The participants were followed up prospectively to compare anatomical and functional outcomes following epiretinal membrane (ERM) surgery among patients with and without high myopia. This describes a matched cohort study, not a nested case-control study. This error has implications for the appropriate statistical analysis, and therefore, the proper interpretation of the observed results. In addition, the statistical tests employed do not account for the matched nature of the study design and therefore are not appropriate. Statistical procedures that account for the matched nature of the study should have been employed. Furthermore, the authors also compared the mean change in best corrected visual acuity and central macular thickness from baseline to 1-year post-surgery within each exposure group (in the text, pages 3-4); however, none of the statistical tests used accounted for the within-person correlation that occurs when taking multiple measurements from the same subject. Specifically, the authors used Student's t-test when paired t-tests should have been used. Authors are strongly encouraged to conduct a reanalysis of their study data using statistical procedures suitable for this study design and provide readers with the appropriate p-values, amending their interpretation as warranted. References 1. Conart J-B, Favel C, Selton J, et al. Outcomes of epiretinal membrane surgery in highly myopic eyes: a case-control study. Br J Ophthalmol. 2014.

Conflict of Interest:

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