Comparison of retinal thickness and choroidal vascularity index after vitrectomy in idiopathic versus diabetic epiretinal membrane

Epiretinal membrane (ERM) formation, frequently encountered in retinal outpatient practice, is commonly caused by idiopathic and diabetic factors. In this surgically treated condition, choroidal changes occur alongside macular changes following ERM peeling. A total of 36 patients who underwent ERM peeling were included in the study: 18 in the idiopathic group and 18 in the diabetic group. Preoperative and postoperative one-month macular and choroidal measurements were obtained using the Heidelberg Engineering Spectralis spectral-domain optical coherence tomography device. The CVI was calculated manually after segmenting the choroid using the ImageJ software. No statistically significant differences were found between the groups in terms of age or sex. Preoperatively, statistically significant differences were found between the groups in terms of central foveal thickness (CFT), superior inner retinal thickness (SIRT), temporal inner retinal thickness (TIRT), and inferior inner retinal thickness (IIRT). Postoperatively, a significant difference was observed only in superior outer retinal thickness (SORT) and the CVI of the Haller layer. When the preoperative and postoperative periods were compared within the idiopathic group, significant differences were found in best-corrected visual acuity (BCVA), CFT, and total CVI. In the diabetic group, preoperative and postoperative comparison revealed significant differences in BCVA, CFT, SIRT, TIRT, IIRT, nasal inner retinal thickness, SORT, Sattler-CC CVI, and total CVI. Although significant differences in retinal thickness were found between the two groups preoperatively, particularly in CFT and in certain sectors, these differences disappeared postoperatively, except for the SORT sector. This finding indicated that, although retinal thickness was greater in diabetic ERM before surgery, the ERM surgery itself may have produced similar effects on retinal thickness in both the idiopathic and diabetic ERMs in the early postoperative period. The choroidal structures were similar between the groups preoperatively; postoperatively, a difference was observed only in the CVI of the Haller layer. This finding suggests that surgery-related inflammatory changes and the associated increase in CVI were more evident in the diabetic group, despite similar preoperative CVI values between idiopathic and diabetic ERM cases.