Pars plana vitrectomy for diabetic macular edema. Internal limiting membrane delamination vs posterior hyaloid removal. A prospective randomized trial

Background Diabetes mellitus, as well as subsequent ocular complications such as cystoid macular edema (CME), are of fundametal socio-economic relevance. Therefore, we evaluated the influence of internal limiting membrane (ILM) removal on longterm morphological and functional outcome in patients with diabetes mellitus (DM) type 2 and chronic CME without evident vitreomacular traction. Method Forty eyes with attached posterior hyaloid were included in this prospective trial and randomized intraoperatively. Prior focal ( n = 31) or panretinal ( n = 25) laser coagulation was permitted. Group I ( n = 19 patients) underwent surgical induction of posterior vitreous detachment (PVD), group II ( n = 20 patients) PVD and removal of the ILM. Eleven patients with detached posterior hyaloid (group III) were not randomized, and ILM removal was performed. One eye had to be excluded from further analysis. Examinations included ETDRS best-corrected visual acuity (BCVA), fluorescein angiography (FLA) and OCT at baseline, 3 and 6 months postoperatively. Main outcome measure was BCVA at 6 months, secondary was foveal thickness. Results Mean BCVA over 6 months remained unchanged in 85% of patients of group II, and decreased in 53% of patients of group I. Results were not statistically significant different [group I: mean decrease log MAR 95% CI (0.06; 0.32), group II: (−0.02; 0.11)]. OCT revealed a significantly greater reduction of foveal thickness following PVD with ILM removal [group I: mean change: 95% CI (−208.95 μm; −78.05 μm), group II: (−80.90 μm: +59.17 μm)]. Conclusion Vitrectomy, PVD with or without ILM removal does not improve vision in patients with DM type 2 and cystoid diabetic macular edema without evident vitreoretinal traction. ILM delamination shows improved morphological results, and appears to be beneficial in eyes with preexisting PVD.