Schisis of the retinal nerve fiber layer in epiretinal membrane surgery: incidence and prognostic significance

The aim of this study was to investigate the incidence and prognostic value of schisis of the retinal nerve fiber layer (sRNFL) in epiretinal membrane (ERM) surgery with internal limiting membrane (ILM) peeling. Material and Methods. The surgical outcomes of 64 patients (66 eyes) with ERM were retrospectively evaluated. The incidence and relationship of sRNFL with surgical characteristics, various OCT biomarkers, and final best-corrected visual acuity (BCVA) were studied. The follow-up period was 1 year. Results. The incidence of sRNFL was 37.9%. In the sRNFL group, the overwhelming majority of ERMs (96%) were classified as stage 3 and 4, subfoveal ellipsoid zone (EZ) defects were also significantly more common (64% versus 14.6%; p <0.001) and perivascular anomalies (84% vs. 9.8%; p <0.001). In addition, the group with sRNFL had a significantly higher preoperative central retinal thickness (CRT): 477.6±78.1 vs. 324.8±102.6 (p <0.001), and the incidence of intraretinal microcysts was 84% and 43.9% (p = 0.002), respectively. The “wave” symptom in the group with sRNFL occurred in 56% of cases; without sRNFL, it occurred in 19.5% (p = 0.003). In the group with sRNFL, en bloc removal of ERM with ILM occurred in 92% of cases, while in the other group - in 51.2% (p <0.001). At the end of the follow-up period, patients in the sRNFL group had a significantly higher incidence of EZ defects (52% vs. 9.8%; p <0.001) and microcystic macular edema (52% vs. 22%; p = 0.014). Visual acuity in the comparison groups, both preoperatively and 1 year after treatment, did not differ significantly (0.34±0.18 vs. 0.38±0.15; p = 0.18 and 0.74±0.28 vs. 0.84±0.17; p = 0.28, respectively). Conclusion: sRNFL is a frequent occurrence that is accompanied by ERM and is significantly more prevalent in more severe stages of ERM (with the presence of ectopic inner foveal layers, EZ defects, and greater CRT). sRNFL is a sign of a strong connection of the ERM with the underlying retina, which is confirmed by a significantly higher frequency of the intraoperative “wave” symptom and an extremely high (92%) probability of removing the ERM en bloc with the ILM in eyes with the presence of this sign.