Analyzing the role of intravitreal bevacizumab and pars plana vitrectomy in nontractional refractory diabetic macular edema.

Abstract

Dear Sir, We read with interest the article by Raizada et al.,[1] comparing the outcome of pars plana vitrectomy versus three doses of intravitreal bevacizumab for nontractional diabetic macular edema (DME). We have the following observations to make. The title does not clarify if the edema was refractory while in the text it is mentioned as refractory macular edema. The authors have not defined what they consider as refractory nontractional DME. Although there is no consensus or international definition for nontractional refractory DME, but, clinicians consider DME as refractory when it is nonresponsive to maximally applied laser photocoagulation and intravitreal drug injections (anti-vascular endothelial growth factor agents [anti-VEGFs] and steroids). The authors have included cases where there was a history of receiving laser or intravitreal drug injections (minimum 3 months from inclusion). This obviously implies that these cases were refractory to the laser as well as intravitreal injections. How do the authors justify repeat injections of bevacizumab to cases who were refractory to it and subsequently compare it with vitrectomy? The results indicate clinically and statistically significant improvement in central macular thickness and best corrected visual acuity in the bevacizumab group. This drives the reader to the fact that these cases were actually not refractory to anti-VEGF therapy. Therefore, the study sample is not representative of cases with refractory DME. The materials and methods section mentions Group 1 as the bevacizumab group and Group 2 as the vitrectomy group but later in the results it is mentioned exactly the opposite. The article also does not indicate what was the preinclusion treatment applied in the respective groups and the number of times such treatment was applied, making the comparison unscientific. Further, the authors have excluded patients with vitreomacular traction. Vitrectomy improves macular edema because of improved oxygenation and removal of inflammatory cytokines.[2] The authors have not indicated the status of vitreous, whether there was a total posterior vitreous detachment or no separation of vitreous from the macular region. Both these situations are nontractional but can have different surgical outcomes. In addition, the authors have used indocyanine green for staining internal limiting membrane (ILM) which is known to be retinotoxic. This can be significant in an already diseased macula. The incidence of intraoperative peripheral breaks in the vitrectomy group in this study is 31.8% while literature suggests an incidence of 1–2%.[3] The authors have not explained the reasons for such an incidence. The authors have stated delayed response in visual improvement as a disadvantage of anti-VEGF therapy while in fact anti-VEGFs afford faster improvement.[4] It is following vitrectomy and ILM peeling that the visual improvement can be delayed because of the varied effects of intraoperative surgical trauma.[5] Finally, we would like to suggest that since the study sample is not well selected, defined, and matched for the purpose of refractory DME, the results of this study and conclusions drawn by it are questionable and need critical evaluation. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.