Epiretinal membranes are a disease of the retinal surface, that may affect visual acuity and cause metamorphopsia. Using vitrectomy with membrane peeling, postoperative improvement of visual acuity and metamorphopsia may be achieved in a majority of patients. Diaz et al. demonstrated that there are postoperative changes in the "nerve fiber layer" after ILM peeling, but in that study, no recording of instrument/tissue interactions was performed using iOCT.

The aim of this study is to examine dipping into retinal tissue with the forceps during grasping of the epiretinal membrane at the starting point of peeling with iOCT.

Epiretinal membranes are a disease of the retinal surface, that may affect visual acuity and cause metamorphopsia, occurring in approximately 20% of the population older than 60 years, as reported by Mitchell et al.. Using vitrectomy with membrane peeling, postoperative improvement of visual acuity and metamorphopsia may be achieved in a majority of patients. The surgical method has been used for some time, the first report on the surgical method of vitrectomy with membrane peeling was published by Machemer and dates back to 1978. Since the introduction of intraoperative optical coherence tomography (iOCT), intraoperative iatrogenically induced changes in retinal tissue can be detected and correlated with postoperative changes. Leisser et al. has been able to record "stretching" of the retinal tissue using this technique and has also been able to record the rarely occurring subfoveal and extrafoveal elevations of the ellipsoidal zone due to membrane peeling. These changes did not significantly affect postoperative visual acuity, according to Leisser et al., but did affect the development of postoperative microscotomas. Nevertheless, iOCT has the potential to document instrument tissue interactions such as dipping into retinal tissue with the forceps during grasping of the ERM at the starting point of membrane peeling. Diaz et al. demonstrated that there are postoperative changes in the "nerve fiber layer" after ILM peeling, but in that study, no recording of instrument/tissue interactions was performed using iOCT.

The aim of this study is to examine dipping into retinal tissue with the forceps during grasping of the epiretinal membrane at the starting point of peeling with iOCT.

Inclusion Criteria:

• Vitrectomy with membrane peeling with iOCT assistance due to an ERM in the time-period from 1.6.2014 to 31.12.2016 (early phase) or 1.11.2020 to 31.7.2022.
• Age 18 and older

Exclusion Criteria:

• iOCT was not used during surgery
• bad image quality, excluding analysis of images

Medical records of patients having undergone pars plana vitrectomy with Membrane Peeling and surgery assisted with iOCT in the time periods from 1.6.2014 to 31.12.2016 (early phase) or 1.11.2020 to 31.7.2022 (later phase) have been selected for data analysis.