Retinal thickness as sensitivity as biomarkers of neurodegeneration in moderate diabetic retinopathy

Abstract

Aims/Purpose: To analyse total retinal thickness (RT) and inner retinal layers (IRL) in Type 2 diabetes mellitus (DM2) patients, measured with swept source OCT (SS‐OCT), and retinal sensibility with microperimetry.Methods: A total of 54 DM2 subjects with moderate diabetic retinopathy (DR) with no signs of diabetic macular oedema (DME) and 73 age‐matched healthy individuals were assessed by SS‐OCT to quantify retinal thickness in the nine macular areas of the Early Treatment Diabetic Retinopathy Study (ETDRS) grid. Retinal sensibility was measured by microperimetry with MAIA.Results: Mean ages were 64.06 ± 11.98 years for the DM2 group and 60.79 ± 8.62 years for the control group. DM2 patients presented lower visual acuity (p < 0.001), RT was significantly higher in the outer temporal area (260.70 ± 19.22 μm in the control group vs. 271.90 ± 37.61 μm in the DM2 group, with p = 0.01), and retinal nerve fibre layer (RNFL) was significantly lower in the outer nasal area (50.38 ± 8.20 μm vs. 45.17 ± 11.25 μm, p = 0.005). Ganglion cells and inner plexiform layers (GCL+) in the parafoveal areas were thinner in DM2 and RT, GCL+ and GCL+ with RNFL (GCL++) significantly diminished with age in the outer ring. A positive correlation between LDL‐C and RNFL and a negative correlation between HDL‐C levels and inner temporal and central RNFL thickness were detected. The central and inner nasal areas presented a negative correlation between RNFL (p = 0.015) and MAIA (p = 0.008), while the outer inferior area showed a positive correlation (p = 0.025).Conclusions: Retinal sensitivity and macular RNFL thickness decrease in DM2 with moderate DR with no DME. Its correlation suggests the existence of diabetic retinal neurodegeneration.