Purpose
Diabetic polyneuropathy may develop even in prediabetic stages. Regarding ocular involvement animal trials suggest electroretinographic changes. Clinical studies show reduced contrast sensitivity in early diabetes. We hypothesized that neurosensory retina may be affected by early diabetic changes that can be detected by spectral domain optical coherence tomography (SD-OCT). A cross-sectional analysis was performed to assess the morphology of the peripapillar retinal layers and visual function.
Methods
Patients were participants of the German Diabetes Study. 130 eyes of 65 adult patients (59± 8 years, 19 female) with DM2 diagnosed less than 12 month before were included. Control group consisted of 90 eyes of 45 healthy adults (57 ±12 years, 15 female) with normal oral glucose tolerance testing. Visual acuitiy (VA), Mars Contrast Sensitivity Test, funduscopy and peripapillar SD-OCT (Spectralis®, Heidelberg Engineering™) were obtained bilaterally, and manual retinal layer segmentation was conducted for 7 peripapillar sections (global(G), nasal-inferior (NI), nasal (N), nasal-superior (NS), temporal-inferior (TI), temporal (T), temporal superior(TS)). SPSS Version22 was used for statistical analysis (p<0.05 statistical significant).
Results
Patients contrast sensitivity was statistically significant reduced compared to controls (p=1.55 vs. 1.61, p=0.001) while VA did not differ significantly. Patients' retinal nerve fibre layer (RNFL) was statistically significant reduced in T (67.6±14 vs. 72.2±13µm, p=0.03) and TI (141.8±22 vs.148.3±21µm,p=0.03) and in the layer from inner segment ellipsoid zone to retinal pigment epithelium in NS (63.1±4 vs. 64.3µm,p=0.005), TS (62.4±4 vs. 63.5±3µm, p=0.02) and G (62.7±3 vs. 63.4±3µm, p=0.05). Patients' RNFL in the N (73.2 ±16 vs. 69.8±14µm, p 0.03) and the complex of inner nuclear layer and outer plexiform layer in NS (42.1±3 vs.40.8±4µm,p=0.006) and TS (44.4±4 vs. 42.8±5µm, p= 0.008) was increased.
Conclusions
Functional changes in terms of worsening contrast sensitivity can be detected in DM2 patients before visual acuity decreases. The alterations of the thickness of inner and outer retinal layers in DM2, detected and quantified by SD-OCT can be interpreted as a form of manifestation of neurodegeneration.