Structural and functional assessment after intravitreal injection of ranibizumab in diabetic macular edema

Purpose To evaluate structure and function improvement in central retina by optical coherence tomography (OCT) and multifocal electroretinography (mf-ERG) in diabetic macular edema (DME) patients after intravitreal injection of ranibizumab (IVR) treatment. Methods Twenty-seven eyes in 27 patients with DME received three consecutive monthly injections of IVR (0.05 ml, 10 mg/ml) and as needed thereafter. The clinical parameters of best-corrected visual acuity (BCVA), central foveal thickness (CFT) and mf-ERG were monitored for 6 months before and after IVR. The findings at baseline, 1, 3 and 6 months were analyzed. Correlation and regression analyses were performed on BCVA, CFT, mf-ERG amplitude and implicit time of the N1 and P1 waves. Results IVR significantly improved visual acuity from the beginning of the treatment ( P < 0.05). There were significant decreases in the CFT compared with the baseline after IVR ( P < 0.05). The mean amplitude of P1 and N1 in the central ring at all examinations increased significantly compared with the baseline ( P < 0.05). The mean P1 and N1 implicit times in the central ring were shortened, but not significantly ( P > 0.05). There were significant correlations of BCVA with CFT, P1 and N1 amplitudes in the central retina ( P < 0.05). Conclusion In addition to the improvement in BCVA and the reduction in CFT, IVR improved macular retinal function, as assessed by mf-ERG, in diabetic eyes. The combination of OCT and mf-ERG for macular evaluation may better assess DME.