Cystoid macular edema after pars plana vitrectomy for idiopathic epiretinal membrane

Background To evaluate the incidence of cystoid macular edema (CME) after 23-gauge pars plana vitrectomy (PPV) with or without combined cataract surgery for the treatment of idiopathic epiretinal membrane (ERM). Methods Retrospective, non-comparative, interventional case series. Data included patient age, indication for surgery, and intra- and post-operative complications. The follow-up lasted 1 year. Best-corrected visual acuity (BCVA logMAR), central foveal thickness (CFT micron-μ) and the incidence of intra-retinal cysts were evaluated.CME was defined as post-operative observation of intra-retinal cysts at optical coherence tomography, preventing improvement or causing reduction of BCVA when compared to the pre-operative value. Statistical analysis was performed to identify the risk factors of CME. Results Two hundred and forty two eyes of 242 patients underwent PPV for the treatment of idiopathic ERM. Statistical analysis showed that the presence of preoperative intra-retinal cysts were associated with persistent CME following surgery (odds ratio 3.89; 95%CI: 1.63-9.28, P = 0.0004). However, postoperative CME occurred in 10 % of eyes that did not show preoperative CME. In addition, there was a significant correlation between the baseline value of CFT and the values of CFT at each time point during the follow up (p < 0.0001), with greater values of the pre-operative thickness correlating to greater values of post-operative thickness. Conclusions Persistent or new CME following surgery for idiopathic ERM are frequently identified after PPV for ERM. The statistical results of the current study suggest that intraretinal cysts and increased preoperative CFT are associated with reduced visual acuity after surgery.