Modified Grid Laser Photocoagulation Versus Pars Plana Vitrectomy With Internal Limiting Membrane Removal in Diabetic Macular Edema

Purpose

To compare the effectiveness of pars plana vitrectomy (PPV) and removal of the internal limiting membrane (ILM) with modified grid laser photocoagulation in diabetic macular edema.

Design

Randomized, comparative, interventional study.

Methods

In this prospective study, 24 eyes of 12 patients with bilateral diabetic macular edema were evaluated. PPV with removal of the ILM was performed at random in one eye of 12 patients (ILM group), and a single session of modified grid laser photocoagulation was performed in the fellow eyes (grid group). Main outcome measures were the foveal thickness measured with optical coherence tomography, preoperative, and postoperative visual acuities. Mann-Whitney U and Wilcoxon tests were used in statistical analysis.

Results

All patients were followed up for 6 months. In the ILM group, mean foveal thickness was 439.2 ± 106.5 μm preoperatively and 219.8 ± 63.2 μm postoperatively (P = .002). In the grid group, mean foveal thickness was 407 ± 100.2 μm preoperatively and 378.5 ± 141.6 μm postoperatively (P = .433). A mean decrease in foveal thickness was found to be 219.4 ± 127.6 μm in the ILM group and 28.5 ± 90.5 μm in the grid group (P = .001). In the ILM group, best-corrected logMAR visual acuity was 0.75 ± 0.41 preoperatively and 0.53 ± 0.41 postoperatively (P = .006). In the grid group, best-corrected logMAR visual acuity was 0.59 ± 0.27 preoperatively and 0.49 ± 0.27 postoperatively (P = .058). Visual acuity improved by 2 or more lines in six eyes (50%) in the ILM group and in three eyes (25%) in the grid group. Visual acuity remained stable in six eyes (50%) in the ILM group and in nine eyes (75%) in the grid group.

Conclusions

PPV with ILM removal appears to be more effective than a single session of modified grid laser photocoagulation in the treatment of diabetic macular edema. Further studies with a large number of patients are required for a more reliable conclusion.