Response to comment on: Posterior sub-Tenon triamcinolone injection in the treatment of postoperative cystoid macular edema secondary to pars plana vitrectomy.

Abstract

Dear Editor, We appreciate the authors for their interest in our article.[1] In our study, we shared the results of 22 patients who underwent posterior sub-Tenon triamcinolone (PSTA) injection for postoperative cystoid macular edema (PCME) after pars plana vitrectomy (PPV).[2] The PCME patients that did not improve despite topical or systemic medical treatment were included. These results are not the results of all patients who developed PCME after PPV, but the results of our refractory patients among them. In some of the similar studies in the literature, injection treatment was preferred after the 6th month, which is considered as the refractory or persistent stage.[3,4] We also waited 6 months to perform PSTA injection—a more invasive procedure—considering the possibility of spontaneous recovery or recovery with other treatment methods. We agree that earlier injection treatment may yield better results. Still, when evaluated with the results of other treatment options applied before the injection, we think we need studies to understand the contribution of early injection to the overall success of post-vitrectomy PCME treatment. An important limitation of studies on PCME after vitrectomy is that it is not currently possible to determine the exact rate of this pathology because a significant amount of PCME secondary to vitrectomy is probably eliminated when we exclude vitreoretinal pathologies (e.g., vascular pathologies, exudative age-related macular degeneration) that may cause postoperative macular edema. Another limitation is diagnosing PCME after vitrectomy by exclusion and by a process of elimination. The PCME after vitrectomy is not easily diagnosed as in PCME after cataract surgery, and it is required to exclude all ophthalmologic and systemic factors that may cause edema. In our study, there were also late-onset cases that were much more difficult to diagnose. We performed a rigorous evaluation, including a detailed, systemic examination of our cases, all of which were unilateral. In our study, the median value for the occurrence of PCME after PPV was 8.5 months. This study included a small number of patients, some with extreme values. As the author mentioned, the median value may better reflect the time edema appears. Among the few studies on this subject, we found that the median value was 5 months in the one with the most similar design to ours.[4] Another limitation of these studies is the impossibility of using optical coherence tomography (OCT) to determine the central macular thickness (CMT) before vitrectomy and to detect the change in thickness caused by vitrectomy in vitreoretinal pathologies with media opacity (intraocular hemorrhage, endophthalmitis, etc.) and retinal detachment. There are also studies that show that CMT increases significantly in pathologies that cause edema, even if clinically significant macular edema has not developed and there are no hyporeflective signs compatible with edema on OCT.[5] In our study, there were patients who had a high and low thickness of the central macula in both recovery and resistance cases. We had patients in whom the retinal anatomical configuration was not very regular due to primary vitreoretinal pathology and patients who developed epiretinal membrane during the follow-up period. Therefore, we did not use CMT and numerical retinal thickness values as criteria but interpreted the changes and regression related to edema in OCT while evaluating the results. We graded changes in OCT at three different stages and tried to simplify the results and make the results of PSTA treatment clearer in this way. To the best of our knowledge, this is the first study to evaluate the application of PSTA in PCME after vitrectomy. Our study included a small number of patients. We think that we will have a better understanding of the subject as prospective studies with larger patient series are conducted. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.