Microperimetry and mfERG as functional measurements in diabetic macular oedema undergoing intravitreal ranibizumab treatment.

To evaluate Microperimetry (MP) and multifocal electroretinogram (mfERG) as whole-macula functional markers of treatment response in naive diabetic macular oedema (DMO) patients undergoing ranibizumab treatment. An exploratory sub-analysis of a prospective study (NCT01947881-CHARTRES). Patients received three monthly ranibizumab injections (loading dose) followed by pro re nata (PRN) regimen during 1 year. At baseline, during and after treatment (Months 0, 3, 6 and 12), subjects were tested using BCVA, OCT, MP and mfERG. MP was performed in the central 12°, and retinal sensitivity was measured overall (mean sensitivity (MS)), and in three concentric rings (R1–R3). mfERG P1 amplitude and implicit time were measured over six concentric rings (R1–R6). Thirty-two eyes were included. MP mean and rings sensitivity were significantly lower in DMO (p < 0.001). After loading dose, a significant improvement in retina sensitivity was observed, particularly in good BCVA responders (MS = +2.28 dB; R1 = +2.33 dB, R2 = +2.20 dB, R3 = +2.25 dB; p = 0.049). Overall retinal sensitivity was significantly correlated with BCVA improvement (r = 0.54; p = 0.026) and inversely correlated with OCT central subfield thickness improvement (r = −0.39; p = 0.026). mfERG amplitude and implicit time were also lower in DMO (p < 0.011). An improvement of mfERG P1 amplitude and implicit time in R1 was noted in good responders after ranibizumab loading dose (+16.49 nV/deg2; p = 0.013 and −0.005 ms; p = 0.048, respectively). When changing to PRN treatment regimen, BCVA was maintained during the 12 months of follow-up but worsening of the visual function was detected by MP and mfERG. Microperimetry and mfERG were able to demonstrate DMO functional improvement after treatment loading dose, as well as early visual changes when treatment regimen was switched to PRN.