Multifocal Electroretinogram Alterations after Intravitreal Ranibizumab Treatment in Diabetic Macular Edema

INTRODUCTION: To assess multifocal electroretinogram (mf-ERG) values in patients with diabetic macular edema (DME) who were treated with intravitreal ranibizumab (IVR).
METHODS: Thirty eyes of patients with DME, who underwent three consecutive monthly injections of IVR and as required thereafter, were evaluated. Best corrected visual acuity (BCVA) (log MAR), optical coherence tomography (OCT) features [diameters of cyst and subretinal fluid, hyperreflective dots (HRDs)], and mf-ERG were evaluated at baseline, 1 month, and 6 months throughout the follow-up period. The correlation of mf-ERG values and OCT features, BCVA, and the duration of disease were investigated.
RESULTS: In the study group, the baseline P1 and N1 amplitudes were significantly lower than the control group, and P1 and N1 implicit times were significantly higher in patients with DME than in the control group in all rings (All p<0.05) The mean response density (P1 amplitude, nV/deg2) values increased over 6 months in rings 1, 2, and 3 (p<0.001, p=0.003, p=0.006). There was a negative correlation between the diameter of the cyst and the initial response density of P1 (for horizontal diameter: r=–0.658, p=0.03; for vertical diameter: r=–0.597, p=0.037; for the area of the cyst, r=–0.603, p=0.021). There was a significant negative correlation between the subretinal fluid and HRD reduction and the response density of P1 increase (all p<0.05). At baseline and 6 months, the correlation between BCVA and the P1 and N1 amplitude of the central ring was significant (for baseline P1: r=–0.649, p=0.01; for N1: r=–0.575, p=0.02; for 6-month P1, r=–0.603, p<0.001; for N1: r=–0.591, p=0.005).
DISCUSSION AND CONCLUSION: The combination of OCT and mf-ERG can be used to evaluate the functional recovery in DME.