To evaluate the association of retinal vessel diameter with NP, DR severity and PPL in diabetic (DM) eyes.

Same day UWF color and fluorescein angiography images from eyes without PRP or non-DR vascular retinal disease were graded for DR severity and presence of PPL. Arteriolar (AD) and venular (VD) calibers and AD:VD ratio (AVR) at 1 DD (inner) and 3.5 DD (outer) from the optic nerve were obtained from UWF color images using a customized semi-automated program. NP area (NPA) and NP index (NPI) were determined for the entire image and the posterior pole (PP), midperiphery (MP) and far periphery (FP).

178 eyes from 109 patients with mean age 52.2±13.9 yrs, DM duration 21.8±12.3 yrs, Hba1c 8.3±1.6%, 52.3% male and 47.7% type1 DM were evaluated. DR severity distribution: 16.9% mild nonproliferative DR (NPDR); 25.3% moderate; 43.8% severe and 14% proliferative DR (PDR). Total, PP, MP and FP NPA and NPI all increased with worsening DR severity (p<0.0001). Outer and inner AVR decreased with increasing DR severity (Outer/Inner: mild 0.92±0.11/0.87±0.12; moderate 0.87±0.09/0.85±0.14; severe 0.85±0.10/0.79 ±0.11; PDR 0.80±0.11/0.79±0.13; p<0.001/p=0.005) while outer VD increased (mild 111.3±11.9µm; moderate 117.3±10.3µm, severe 116.9±14.3µm and PDR 124.7±16.2µm; p<0.001). Outer and inner AD and inner VD showed no significant correlation with DR severity. In eyes with PPL (N=68), as DR severity increased outer AVR decreased (p=0.005), outer AD decreased (p=0.021) and outer VD increased (p=0.003). In eyes without PPL (N=110), only outer AVR decreased with increasing DR severity (p=0.048).

Non-invasively measured retinal vessel caliber changes are correlated with retinal NP and DR severity. Eyes with PPL have increased venous dilation and arterial narrowing, which become greater with increasing DR severity - a finding not observed in eyes without PPL. These data suggest that PPL are associated with greater vascular pathology, thus possibly contributing to accelerated DR progression