To evaluate the changes in each retinal layer thickness according to preoperative optical coherence tomography (OCT) patterns after idiopathic epiretinal membrane (ERM) removal and to investigate the correlation between retinal layer thickness and visual improvement.

The medical records of 63 patients (63 eyes) who underwent vitrectomy with internal limiting membrane (ILM) peeling for idiopathic ERM and followed for more than 6 months were retrospectively reviewed. The OCT images of preoperative idiopathic ERM were classified into 3 patterns being flat, convex, and concave. Then, the changes of each retinal layer thickness were compared among OCT patterns and the correlations between retinal layer thickness and visual improvement were analyzed.

Improvement in visual acuity was measured in the following order: concave, flat, and convex patterns. The patients with the convex pattern only showed significant improvement of visual acuity. Ganglion cell layer plus inner plexiform layer (GCL + IPL), inner nuclear layer (INL), and outer plexiform layer (OPL) thicknesses were significantly larger in preoperative ERM patients than in normal controls in the following order: convex, concave, and flat patterns. Retinal layer thickness decreased significantly in GCL + IPL and INL after surgery in convex, flat, and concave patterns, in that order. Generally, preoperative retinal layer thickness and postoperative visual acuity were not correlated. However, improvement of visual acuity was significantly related to GCL + IPL and INL thicknesses in the convex pattern and IPL thickness in the flat pattern.

In patients with idiopathic ERM, preoperative difference in each retinal layer thickness according to preoperative OCT patterns was observed. After ERM removal, reduction of each retinal layer thickness and specific retinal layer related to visual improvement was different according to preoperative OCT patterns.