Retinal and choroidal features in patients with diabetic peripheral neuropathy: a stratified analysis by retinopathy status

Background Recent research is progressively elucidating that diabetic neurodegenerative and microvascular changes of peripheral nerves may be detectable in the eye fundus. And we aimed at assessing retinal and choroidal alterations in patients with diabetic peripheral neuropathy (DPN) using ultra-wide-field swept-source optical coherence tomography angiography (UWF-SS-OCTA). Methods This cross-sectional observational study enrolled 65 eyes from 35 DPN patients and 120 eyes from 64 diabetic patients without DPN (NDPN) and classified them by retinopathy status: no retinopathy (NDR) or nonproliferative diabetic retinopathy (NPDR)(DPN/NDPN-NDR or DPN/NDPN-NPDR). Assessed retinal and choroidal metrics included foveal avascular zone (FAZ)-related parameters, vessel flow and linear densities (VFD, VLD), choroidal vascularity/stromal volume (CVV, CSV), thickness, and volume in fovea-centered 12 mm ETDRS subregions, central area, peripheral area, and the whole 24×20 mm 2 UWF-SS-OCTA images. Generalized estimating equation was used to compare imaging parameters between groups. Results DPN-NDR eyes showed significantly increased parafoveal inner retinal thickness than NDPN-NDR eyes (median 128.50, IQR 123.63-132.75 vs. median 121.13, IQR 114.63-129.31; P = 0.005). DPN-NPDR eyes had increased foveal VFD (median 14.50, IQR 10.25-20.25 vs. median 9.50, IQR 5.00-15.75; P = 0.031) and VFD in the 300 μm annulus around FAZ (median 21.11, IQR 13.37-28.33 vs. median 10.88, IQR 7.93-19.17; P = 0.008) of the deep capillary plexus than NDPN-NPDR eyes. Regarding the choroid, DPN-NDR eyes had significantly lower central CVV (median 55.67, IQR 44.10-79.55 vs. median 72.03, IQR 53.08-94.14; P = 0.044), while peripheral CSV was increased in DPN-NPDR eyes compared to NDPN-NPDR eyes (median 103.19, IQR 80.45-116.95 vs. median 79.72, IQR 62.67-90.36; P = 0.016). VFD in the choriocapillaris or the large and medium choroidal vessel layer showed no significant differences between DPN and NDPN groups ( P > 0.05). Conclusions Retinal and choroidal changes detected in DPN patients by UWF-SS-OCTA suggested the correlation between diabetic neurodegeneration and microangiopathy in different organs.