Microvascular changes after internal limiting membrane peeling in proliferative diabetic retinopathy using optical coherence tomography angiography: a randomized controlled trial

Purpose The aim of this study was to compare the macular microvasculature, using optical coherence tomography angiography, in proliferative diabetic retinopathy (PDR) patients for whom pars plana vitrectomy (PPV) with or without internal limiting membrane (ILM) peeling was done. Patients and methods This is a prospective randomized controlled trial that included 36 PDR patients with non-clearing vitreous hemorrhage or tractional retinal detachment threatening the macula. The patients were randomized in a 1:1 ratio to undergo PPV and silicone oil (SO) tamponade with or without ILM peeling (18 patients in each group). The primary outcome measures were macular vascular density (VD) and foveal avascular zone (FAZ) area at 3 and 6 months after SO removal. The secondary outcome measures were postoperative LogMAR best-corrected visual acuity (BCVA) and the incidence of epiretinal membrane (ERM) formation. Results There was a significantly higher superficial parafoveal VD (total=37.5±4.5% vs. 32.7±4.4%, inferior-hemi=38.2±5.5% vs. 30.7±7.4%, temporal=37.8±5.1% vs. 31.7±4.2%, and inferior=39.4±6.6% vs. 31.6±8.9%) in the ILM nonpeeled group compared to the peeled group, respectively ( P =0.003, 0.001, <0.001, and 0.005, respectively). There was no statistically significant difference in the deep VD or FAZ parameters between the two groups at 6 months following SO removal ( P >0.05). The LogMAR BCVA was comparable at 6 months postoperatively (0.9±0.3 in the peeled group compared to 1.1±0.2 in the nonpeeled group, P =0.350). However, there was a significantly higher incidence of ERM formation in the ILM nonpeeled group (61.1%) compared to the peeled group (5.6%), ( P <0.001). Conclusion ILM peeling in the PDR patients undergoing PPV reduced the superficial parafoveal VD with a lower risk of ERM formation compared to nonpeeling. Despite these differences, the final BCVA was comparable between the two groups.