Objective: To investigate the characters of multifocal electroretinogram (mfERG) in different grades of diabetic macular edema defined by optical coherence tomography (OCT).
Methods: MfERG and OCT were performed in 57 eyes of diabetic macular edema (DME) patients and 35 eyes of the control group. According to the macular thickness measured by OCT, eyes with DME were divided into three groups: mild, moderate and severe DMEs.
Results: In mild DME, the response densities of N(1) were attenuated in ring 4[(14.67 ± 4.91) nV×deg(-2)] to ring 5 [(11.65 ± 3.89) nV×deg(-2)] respectively (t = 2.179, 2.529; P < 0.05). The latencies of P(1) was prolonged significantly in ring 3 [(40.61 ± 4.10) ms] (t = -2.133, P < 0.05). In moderate DME, the response densities of P(1) and N(1) were attenuated in ring 1 [(149.50 ± 29.01) nV×deg(-2)], ring 2 [(59.33 ± 25.96) nV×deg(-2)], ring 3 [(41.83 ± 9.78) nV×deg(-2)], and ring 5 [(22.00 ± 5.52) nV×deg(-2)] respectively (t = 3.610, 2.168, 2.627, 3.445; P < 0.05). The latencies of P(1) and N(1) were prolonged significantly in ring 3 [(42.86 ± 4.72) ms], ring 4 [(44.33 ± 5.56) ms], ring 5 [(46.31 ± 4.72) ms] (t = -3.150, -3.210, -3.968; P < 0.05) and ring 3 [(23.05 ± 3.06) ms], ring 4 [(22.41 ± 3.36) ms] (t = -2.845, -2.098; P < 0.05) respectively. In severe DME. The response densities of P(1) and N(1) were attenuated in ring 1 [(110.00 ± 20.68) nV×deg(-2)], ring 2 [(62.40 ± 27.90) nV×deg(-2)], ring 3[(39.20 ± 19.65) nV×deg(-2)], ring 5 [(21.60 ± 11.12) nV×deg(-2)] (t = 7.135, 1.782, 2.214, 2.609; P < 0.05) and ring 1 [(41.63 ± 39.17) nV×deg(-2)], ring 3 [(16.63 ± 5.81) nV×deg(-2)], ring 4 [(11.20 ± 7.42) nV×deg(-2)], ring 5 [(9.05 ± 4.63) nV×deg(-2)] (t = 2.714, 2.282, 2.736, 2.858; P < 0.05) respectively. The latencies of P(1) and N(1) were prolonged significantly in ring 1 [(35.12 ± 8.44) ms], ring 3 [(40.44 ± 2.10) ms], ring 4 [(42.80 ± 3.74) ms] (t = 3.426, -2.710, -3.120; P < 0.05) and ring 4 [(23.36 ± 4.05) ms] (t = -2.572; P < 0.05) respectively.
Conclusion: As the progress of DME, the thickness of macular fovea had significant correlation with responses of multifocal electroretinogram in patients with moderate or severe DME. MfERG combined with OCT can evaluate the changes of morphology and local retinal function in macula area objectively and quantitatively.