Purpose: 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.
Methods: 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).
Results: 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.
Conclusions: 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.