Pars plana vitrectomy (PPV) is a commonly done procedure in patients with idiopathic epiretinal membrane (iERM) so that their vision can get better. Postoperative visual field defects (VFDs) were reported in the past. However, they are usually observed when the recent PPV system is used, and also the frequency of VFDs as estimated by approved automated perimetry, which have not been notified nor reported were studied in this study.

Data was collected of 30 eyes that underwent PPV for iERM during the duration of February 2016–June 2019 and had preoperative and postoperative visual field measurements using standard automated perimetry (Humphrey visual field analyzer 30-2 program) were checked retrospectively. Eyes with diseases other than iERM VFDs were excluded which also include moderate-to-severe cataract or preoperative.

VFD, defined by Anderson and Patella’s criteria, was found in 73.3% of the eyes 1 month after PPV. After age adjustment, internal limiting membrane (ILM) peeling was identified as a risk factor for postoperative VFD (p=0.035; 95% CI 1.173 to 92.8). Postoperative VFD was frequently observed nasally (86.4%, p=0.002), and on optical coherence tomography measurements, ganglion cell layer (GCL) thinning was found temporal to the fovea (p=0.008). Thinning of the superior and inferior retinal nerve fiber layers and the GCL temporal to the fovea were significant in the eyes after ILM peeling (all p<0.05).

ILM peeling may cause inner retinal degeneration and lead to the development of VFDs after PPV, which should be further examined.