Multifocal Electroretinogram in Diabetic Macular Edema and its Correlation with Visual Acuity and Different Optical Coherence Tomography Features

Purpose: To evaluate multifocal electroretinogram (mfERG) changes in eyes with diabetic macular edema (DME) and it’s correlation with optical coherence tomography (OCT) features and visual acuity (VA). Methods: Fifty-four eyes of 27 subjects with bilateral DME due to non-proliferative diabetic retinopathy were evaluated. Sixty-one scale hexagon mfERG responses were recorded. Components of the first order kernel of N1, N2, and P1 in two concentric rings centered on the foveal center were measured in both groups. Macular thickness was measured by OCT in each segment of the concentric rings and mfERG rings were superimposed on macular thickness map. Macular ischemia has been ruled out by fluorescein angiography. Correlation between VA, localized macular thickness, and retinal structural abnormalities with mfERG parameters at each segment was evaluated. Results: Mean of BCVA was 0.5±0.3 in logMAR and central macular thickness was 392.6±123.4 microns. Retinal thickness was correlated significantly with N1 and N2 amplitude in central and inferior segment of first ring, respectively (p=0.02 and p=0.001). Outer retinal layer disruption was 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 retinal inner layers (DRIL) in inferior and superior segment of first ring was 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 locations. There was no correlation between BCVA and either mfERG or OCT.Conclusion: Central retinal thickness or different OCT biomarkers (as an anatomical indicator of diabetic macular edema) can be correlated with different mfERG features. Predictive models such as those described in this report, may make it possible to identify correlation of specific anatomic and functional characteristics in diabetic macular edema