PURPOSE: To evaluate whether predominantly peripheral lesions (PPL), regional differences in retinal vessel diameters and oximetry changes are associated with the extent of retinal nonperfusion (NP) on ultrawide field fluorescein angiography (UWF-FA) in diabetic eyes.
METHODS: Vessel diameters, ETDRS diabetic retinopathy (DR) severity and presence of PPL were evaluated on UWF 200 degree images. Retinal oximetry and UWF-FA were obtained at the same visit. Vessel calibers at 1 disc diameter (DD, inner-AVR) and 3.5 DD (outer-AVR) from the center of the disc were measured using a customized semi-automated computer program. Retinal NP (mm2) was measured from UWF-FA images. Venous oxygen saturation (VO2, %) and arteriovenous difference (A-V, %) were calculated within a 2 DD ring centered on the optic disc.
RESULTS: A total of 39 eyes from 20 subjects with mean age 40.7±10.7 yrs, diabetes duration 21.1±10.4 yrs, HbA1c 7.7%±1.1, 65.0% male and 75.0% type 1 diabetes were evaluated. DR severity was no DR 10.3%(4 eyes), mild nonproliferative DR (NPDR) 48.7%(19), moderate 20.5%(8), severe 10.3%(4), and proliferative DR 10.3%(4). PPL were present in 56.4%(22) of eyes and associated with increasing DR severity (p=0.006) as well as increasing NP & VO2, and decreasing A-V. In all eyes, NP was associated with increasing DR severity (r=0.60, p<0.0001) and increasing outer venular diameters (r=0.46,p=0.03). In eyes with PPL (N=22), increasing NP was correlated with increasing inner-AVR (r=0.43, p=0.04) and larger differences between outer- and inner-AVR (r=0.44, p=0.04). In eyes without PPL (N=17), NP was correlated with increasing inner (r=0.45, p=0.0370) and outer (r=0.68, p=0.0021) venular diameters. Correlation between inner and outer AVR was present only in eyes with no PPL (r=0.50, p=0.03) suggesting differences between inner and outer zones in eyes with PPL (r=0.29, p=0.18).
CONCLUSIONS: In this cohort, increasing NP was associated with increasing DR severity, venular dilation, increased VO2 and decreased A-V, suggesting greater areas of retinal ischemia, presence of venous shunting and reduced retinal oxygen utility. In eyes with PPL, regional differences in vessel caliber were correlated with increasing peripheral NP and provide further evidence that the risk of progression with PPL is driven by retinal ischemia.
