Choroidal Neovascularization in Pathologic Myopia

We read with interest the article titled “Choroidal Neovascularization in Pathologic Myopia: Intravitreal Ranibizumab Versus Bevacizumab—A Randomized Controlled Trial.” We would like to congratulate the authors for conducting a study comparing the two treatment options for choroidal neovascularization in pathologic myopia. However, we would like to seek a few clarifications regarding the methodology and the conclusions.

The authors mention a randomized controlled trial (RCT) in the title. Based on the guidelines for an RCT, the authors have not clarified the methodology of calculating the sample size. The power of the study is extremely less for an RCT allowing for a large false-negative error in the results. To define this study as an RCT with an ideal α error of 5% and a β error of 20% would require approximately 216 patients in each arm for best-corrected visual acuity. Going by the incidence of the disease, a multicenter study seems the only plausible way to conduct an RCT in this case.

To compare the best-corrected visual acuity results, the authors used a 1-tailed paired t test, suggesting that the study is a noninferiority or an equivalence study. In such a case, it becomes essential to define a margin of clinical equivalence by deciding the largest difference of means that is clinically acceptable. This would make the results clinically applicable. Although none of the cases have had any complications, the proportional confidence interval of a complication rate could be as high as 25% for such a small sample size. The authors’ interpretation regarding the need for prophylactic laser in predisposed eyes does not seem to be based on the results of the study, but rather seems to be an extrapolation beyond the data.

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Jan 17, 2017 | Posted by in OPHTHALMOLOGY | Comments Off on Choroidal Neovascularization in Pathologic Myopia

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