Multifocal Electroretinogram in Diabetic Macular Edema; Correlation with Visual Acuity and Optical Coherence Tomography

Purpose: To evaluate multifocal electroretinogram (mfERG) changes in eyes with diabetic macular edema (DME) and investigate any possible correlation with optical coherence tomography (OCT) features and visual acuity (VA).Methods: Fifty-four eyes of 27 subjects with DME due to non-proliferative diabetic retinopathy were evaluated. All patients underwent a complete ophthalmic examination. Sixty-one scaled hexagon mfERG responses were recorded. Components of the first order kernel of N1, N2, and P1 in two concentric rings centered on the fovea were measured in both groups. Macular thickness was measured by OCT in each segment of the concentric rings. mfERG parameters were superimposed on macular thickness map . Any correlation among VA, localized macular thickness, inner and outer retina structural abnormality and mfERG parameters at each segment was evaluated.Results: There was no any significant correlation between VA and mfERG parameters. Macular thicknesses were correlated significantly with N1 and N2 amplitude in central and inferior segment of first ring, respectively (p=0.02 and p=0.001). There was no any significant correlation between macular thickness and mfERG parameters in any other segments. Outer retina disruption was significantly correlated with prolonged P1 implicit time in center and the two concentric rings at corresponding location (p=0.001,p=0.007 and p=0.005 respectively). Disorganization of retina inner layer (DRIL) in inferior and superior segment of first ring was significantly associated with reduced P1 amplitude (p=0.037 and p=0.047 respectively). This phenomenon was associated with reduced N2 amplitude in inferior and superior segment of second ring (P=0.021and P=0.003 respectively) at corresponding location.Conclusion: Combined use of OCT with mfERG is more beneficial for macular evaluation in patients with DME. Predictive models such as those described in this report, may make it possible to identify individuals, who are at risk for developing diabetic retinopathy induced retinal structural changes and it’s location