Increased risk of cystoid macular edema after cataract surgery in eyes previously vitrectomized for idiopathic epiretinal membrane

Purpose: To assess the rate and risk factors of cystoid macular edema (CME) both after isolated vitrectomy and after subsequent phacoemulsification in eyes with primary non-complicated rhegmatogenous retinal detachment (RRD) or idiopathic epiretinal membrane (ERM). Methods: Retrospective observation of institutional patients undergoing vitrectomy for RRD or vitrectomy with internal limiting membrane peeling for ERM from 2016 to 2021, further analyzing those who later underwent phacoemulsification. The CME rate was assessed within the first 6 months after both vitrectomy and cataract surgery. Results: We included 187 phakic eyes with ERM and 311 with RRD undergoing isolated vitrectomy. Post-vitrectomy CME occurred in 12.8% of ERM cases compared to 1% in RRD cases ( p <0.0001). Stage-4 ERMs and intraoperative laser were found associated with CME. After uncomplicated phacoemulsification, the CME rate was higher in eyes vitrectomized for ERM (13.8%) compared to RRD (2%, p= 0.0055). Post-vitrectomy CME was found to be associated with an increased risk of post-cataract CME (OR 13.588, p =0.0187). Conclusions: In eyes undergoing phacoemulsification post-vitrectomy, the risk of CME is higher when vitrectomy was performed for ERM compared to RRD. The ERM-related intraretinal changes, together with the required surgical stress, may play a role in making these eyes more susceptible to CME.