Retinal vascular caliber association with nonperfusion and diabetic retinopathy severity depends on vascular caliber measurement location.

Abstract Purpose To evaluate the association of retinal nonperfusion and diabetic retinopathy (DR) severity with location of vascular caliber measurement using ultrawide field (UWF) imaging. Design Retrospective image review Subjects Adult subjects with diabetes mellitus. Methods All images from subjects with same day UWF fluorescein angiography (FA) and color imaging (CI) were evaluated. DR severity and predominantly peripheral lesions (PPL) were graded from UWF-CI. Nonperfusion was quantified using UWF-FA in defined retinal regions [posterior pole (PP), mid-periphery (MP), far-periphery (FP)]. Retinal vessel calibers were measured at an inner and outer zone centered on the optic disc. Main Outcome Measures Nonperfusion index (NPI) in the PP, MP and FP. Mean arteriole and venule diameter in the inner and outer zones. Results 285 eyes of 193 patients [(24.9% mild nonproliferative DR (NPDR), 22.8% moderate, 37.5% severe and 14.7% proliferative DR (PDR)] were reviewed. There were no significant associations between inner zone arteriolar diameter and retinal NPI overall or in any retinal region. In the outer zone, eyes with thinnest arteriolar calibers (Q1) were associated with a 1.7-2.4-fold increase in nonperfusion across all retinal regions compared to the remaining eyes [P=0.002 (PP) to 0.048 (FP)]. In the outer zone, the percentage of eyes in the thinnest quartile of retinal arteriolar diameter increased with worsening DR severity (10% in mild NPDR and 31% in PDR, p=0.007). This association was not observed when measured within the inner zone (p=0.129). All venular caliber associations were not statistically significant when corrected for potentially confounding factors. Thinner outer zone retinal arteriolar caliber (Q1) was more common in eyes with PPL compared to eyes without PPL (34.1% vs 20.8%, p=0.017) as were thicker outer venular calibers (Q4) (33% vs 21.3%, p=0.036). Presence of PPL was associated with thinner outer zone arteriolar caliber (109.7±26.5 vs 123.0±29.5, p=0.001). Conclusions The association of vascular caliber with nonperfusion and DR severity differs based upon the retinal location at which vascular caliber is measured. Peripheral arterial narrowing is associated with increasing nonperfusion, worsening DR severity and presence of PPL. In contrast, inner zone retinal arteriolar caliber is not associated with these findings.