Abnormalities of retinal ganglion cell complex at optical coherence tomography in patients with type 2 diabetes: a sign of diabetic polyneuropathy, not retinopathy

Aims: To compare optical coherence tomography (OCT)-derived neuro-retinal parameters in patients with type 2 diabetes and non-diabetic controls and to evaluate their correlation with diabetic retinopathy (DR) and polyneuropathy (DPN). Methods: One-hundred consecutive patients with type 2 diabetes were examined by spectral–domain (SD) OCT for evaluating ganglion cell complex (GCC) and retinal nerve fibre layer (RNFL) thickness and two new pattern-based quantitative measures of GCC damage, global and focal loss volume (GLV and FLV). Fifty sexand age-matched non-diabetic subjects served as control. Results: RNFL thickness (101.0 ± 10.6 vs. 106.4 ± 10.3 μm, P = 0.003) was significantly lower and GLV (6.58 ± 4.98 vs. 4.52 ± 3.10 %, P = 0.008) and FLV (1.90 ± 1.97 vs. 0.89 ± 0.84 %, P b 0.0001) were significantly higher in diabetic versus control subjects. The OCT parameters did not differ significantly according to DR grade. Conversely, RNFL thickness was lower and GLV and FLV were higher in patients with versus those without DPN, and the extent of changes increased significantly with quartiles of DPN score. At both bivariate and multivariate analysis, OCT parameters, especially FLV, correlated significantly with DPN measures. Conclusions: The GCC is significantly affected in patients with type 2 diabetes and SD-OCT might represent a useful tool to detect DPN, but not DR in these individuals.