Evaluation of the grasp site after peeling of epiretinal membranes with different ILM forceps

Epiretinal membranes (ERM), a macular disorder affecting the vitreoretinal surface, lead to a decrease in visual acuity and increase in metamorphopsia. Peeling of ERM during vitrectomy has the potential for improvements of visual acuity and metamorphopsia. Nevertheless, starting membrane peeling displays a critical step, as membranes are often difficult to grasp and there are risks for retinal damage during grasping of the ERM at the starting location. Aim of the study was to analyze associations of instrument tissue interactions at the grasp site with possible thinning of superficial retinal layers, with special respect to the ganglion cell layer, when using two different ILM forceps. This randomized trial included patients scheduled for pars plana vitrectomy with membrane peeling due to an idiopathic ERM. Patients were allocated to either group A (ILM forceps with a laser-modified microstructure on the branches), or group B (conventional ILM forceps). Instrument tissue interactions were analysed from surgical video-documentation including continuous intraoperative optical coherence tomography (OCT) and associations to anatomical (OCT) and functional (microperimetry) outcomes were examined. Among 58 patients included into the study, there were no significant differences in the number of grasp attempts between both ILM forceps with a median number of 6 grasp attempts in group A and 4 grasp attempts in group B (p = 0.23, Mann Whitney U test). Dipping of the forceps into retinal tissue was comparable between both forceps, except for fewer incidences of dipping into retinal tissue in group A among patients with partly adherent ERMs. Associations between postsurgical defects at the superficial retinal layers and instrument tissue interactions during grasping could be found only for a minority of patients in the postsurgical OCTs, and there were no obvious associations of postsurgical retinal defects to functional changes in microperimetry. There were no significant differences in the number of grasp attempts between both ILM forceps, with a trend in favour of the conventional ILM forceps. However, the ILM forceps with a laser-modified microstructure on the branches led to fewer situations with dipping of the ILM forceps into retinal tissue.