To investigate correlations between clinical and histopathologic characteristics of idiopathic epiretinal membrane (ERM).

Retrospective interventional case series.

In total, 87 eyes from 87 patients with idiopathic ERM who underwent pars plana vitrectomy with peeling of the ERM from 2019 to 2020 were included.

The outcomes of clinical ophthalmologic examination, including measurement of best-corrected visual acuity (BCVA) and spectral-domain optical coherence tomography (SD-OCT), before and after surgery were reviewed. Surgical specimens were fixed in formalin and embedded in paraffin for histologic and immunohistochemical (IHC) analysis.

The association between morphological characteristics revealed on SD-OCT images and the cellular composition of the surgically excised ERM demonstrated with IHC staining were the main outcome measures. Changes in the BCVA and central macular thickness (CMT) were assessed through a comparison of preoperative and postoperative measurements.

Based on SD-OCT morphological characteristics in the foveal area, 15 cases were classified into group 1A (mainly outer retinal thickening), 39 into group 1B (more tenting of the outer retina and distorted inner retina), and 33 into group 1C (prominent inner retina thickening). Overall, postoperative final BCVA and CMT at 1 year improved in all groups. Patients who presented with better initial BCVA exhibited a more favorable final BCVA. ERMs in group 1C demonstrated the greatest reduction in CMT compared with those in groups 1B and 1A, but the final CMT did not differ among the groups. A negative correlation between the density of hyalocytes (P=0.003) and myofibroblasts (P=0.047) was noted between the three groups. Total cell density and glial cell density of the ERMs were strongly associated with poor final BCVA and BCVA improvement.

The present study provides new histopathologic information regarding the formation and progression of idiopathic ERM. Glial cell proliferation plays a predominant role in these processes. ERMs with high cellularity and glial cell density may cause damage to the retina structure, resulting in poor postoperative visual outcomes. These findings provide additional evidence supporting early surgical intervention in patients with idiopathic ERM reported with visual disturbance.