Retinal Functional Impairment in Diabetic Retinopathy

Abstract

Background: Diabetic retinopathy (DR) is a neurodegenerative disease of the retina. The aim of our study was to analyze latency changes in a full-field electroretinogram (ERG) in patients with type 2 diabetes.

Material: This prospective study included 15 diabetic patients without DR, 16 diabetic patients with non-proliferative DR, 14 patients with pre-proliferative DR, 15 patients with proliferative DR, and 14 age-matched controls. All the participants underwent ophthalmologic examination and full-field ERGs. The ERGs were recorded with the Metrovision MonPackOne system. The latencies were analyzed for "a"- and "b"-waves in the dark-adapted (DA) 0.01 ERG, DA 3.0 ERG, DA oscillatory potentials, light-adapted (LA) 3.0 ERG, and 30 Hz flicker ERG.

Results: The delayed responses of healthy subjects compared to diabetic patients without DR were the DA oscillatory potentials (25.45 ± 1.04 ms vs. 26.15 ± 0.96 ms, p = 0.027). When comparing diabetic patients without DR and with non-proliferative DR, we did not obtain statistically significant delays. Significant delays in the DA 0.01 "b"-wave (61.91 ± 5.52 ms vs. 66.36 ± 8.12 ms, p = 0.029), DA 3.0 "b"-wave (41.01 ± 2.50 ms vs. 44.16 ± 3.78 ms, p = 0.035), and LA 3.0 "a"-wave (16.21 ± 0.91 ms vs. 16.99 ± 1.16 ms, p = 0.045) were found between non-proliferative DR and pre-proliferative DR. When comparing the groups of patients with pre-proliferative DR and proliferative DR, the LA 3.0 ERG "b"-wave (32. 63 ± 2.53 ms vs. 36.19 ± 3.21 ms, p < 0.0001), LA 30 Hz flicker ERG "a"-wave (19.56 ± 3.59 vs. 21.75 ± 4.74 ms, p= 0.025), and "b"-wave (32.23 ± 4.02 vs. 36.68 ± 3.48 ms, p = 0.017) were delayed.

Conclusions: the electrophysiological findings from our study indicate that there is a substantial dysfunction of the neural retina in all stages of DR.

Keywords: diabetes mellitus; diabetic retinopathy; full-field ERG.

Figure 1

Standard ERG in a healthy individual. DA—dark adapted; LA—light adapted; RE—right eye; LE—left eye; A1—a-wave; B1—b-wave; O1—OP N1; O2—OP N2.

Figure 2

Comparison of mean values of l DA 0.01 a-wave latencies between normal subjects (control) and the subgroups of patients with diabetes mellitus without DR (DR-), patients with non-proliferative diabetic retinopathy (NDR), patients with pre-proliferative diabetic retinopathy (PPDR), and patients with proliferative diabetic retinopathy (PDR). * p < 0.05; ** p < 0.01.

Figure 3

Comparison of mean values of DA 0.01 b-wave latencies between normal subjects (control) and the groups of patients with diabetes mellitus without DR (DR-), patients with non-proliferative diabetic retinopathy (NDR), patients with pre-proliferative diabetic retinopathy (PPDR), and patients with proliferative diabetic retinopathy (PDR). * p < 0.05; ** p < 0.01; *** p < 0.001.

Figure 4

Comparison of mean values of DA 3.0 a-wave latencies between healthy subjects (control) and the subgroups of patients with diabetes mellitus without DR (DR-), patients with non-proliferative diabetic retinopathy (NDR), patients with pre-proliferative diabetic retinopathy (PPDR), and patients with proliferative diabetic retinopathy (PDR).

Figure 5

Comparison of mean values of DA 3.0 b-wave latencies between healthy subjects (control) and the groups of patients with diabetes mellitus without DR (DR-), patients with non-proliferative diabetic retinopathy (NDR), patients with pre-proliferative diabetic retinopathy (PPDR), and patients with proliferative diabetic retinopathy (PDR). * p < 0.05; ** p < 0.01; *** p < 0.001.

Figure 6

Comparison of mean values of DA 3.0 OP N1 wave latencies between healthy subjects (control) and the groups of patients with diabetes mellitus without DR (DR-), patients with non-proliferative diabetic retinopathy (NDR), patients with pre-proliferative diabetic retinopathy (PPDR), and patients with proliferative diabetic retinopathy (PDR). * p < 0.05; ** p < 0.01; *** p < 0.001.

Figure 7

Comparison of mean values of DA 3.0 OP N2 wave latencies between healthy subjects (control) and the groups of patients with diabetes mellitus without DR (DR-), patients with non-proliferative diabetic retinopathy (NDR), patients with pre-proliferative diabetic retinopathy (PPDR), and patients with proliferative diabetic retinopathy (PDR). * p < 0.05; ** p < 0.01; *** p < 0.001.

Figure 8

Comparison of mean values of LA 3.0 a-wave latencies between healthy subjects (control) and the groups of patients with diabetes mellitus without DR (DR-), patients with non-proliferative diabetic retinopathy (NDR), patients with pre-proliferative diabetic retinopathy (PPDR), and patients with proliferative diabetic retinopathy (PDR). * p < 0.05; ** p < 0.01.

Figure 9

Comparison of mean values of LA 3.0 b-wave latencies between healthy subjects (control) and the groups of patients with diabetes mellitus without DR (DR-), patients with non-proliferative diabetic retinopathy (NDR), patients with pre-proliferative diabetic retinopathy (PPDR), and patients with proliferative diabetic retinopathy (PDR). *** p < 0.001.

Figure 10

Comparison of mean values of LA 30 Hz flicker a-wave latencies between healthy subjects (control) and the groups of patients with diabetes mellitus without DR (DR-), patients with non-proliferative diabetic retinopathy (NDR), patients with pre-proliferative diabetic retinopathy (PPDR), and patients with proliferative diabetic retinopathy (PDR). * p < 0.05; ** p < 0.01.

Figure 11

Comparison of mean values of LA 30 Hz flicker b-wave latencies between healthy subjects (control) and the groups of patients with diabetes mellitus without DR (DR-), patients with non-proliferative diabetic retinopathy (NDR), patients with pre-proliferative diabetic retinopathy (PPDR), and patients with proliferative diabetic retinopathy (PDR). * p < 0.05; ** p < 0.01; *** p < 0.001.