Comparison of photoreceptor outer segment length in diabetic and idiopathic epiretinal membranes

Purpose Idiopathic and diabetic epiretinal membranes (ERMs) differ significantly in terms of macular morphology. Our aim was to compare the photoreceptor outer segment (PROS) length in diabetic and idiopathic ERMs before and after surgery. Methods Fifty-two eyes of 50 patients who underwent pars plana vitrectomy (PPV) due to idiopathic and diabetic ERMs were included in this retrospective case series. All of the patients underwent ERM and internal limiting membrane (ILM) removal. The patients had been followed up 6 months postoperatively. Spectral-domain optical coherence tomography (OCT) was used to measure the PROS length, overall PR length and central foveal thickness (CFT). Results The PROS length, overall PR length, and CFT were statistically significantly lower at all the postoperative visits when compared to preoperative values in both the idiopathic and diabetic ERM groups (P<0.001). The amount of decrease in PROS and overall PR length were similar in both groups after surgery (P>0.05). There was no relation between amount of PROS length change and visual acuity gain in both groups (P>0.05). Conclusions Postoperative change of PROS length was similar in idiopathic and diabetic ERMs. PROS length change may not be an indicator of postoperative visual acuity.