Methods for evaluation of retinal microvascular abnormalities associated with hypertension/sclerosis in the atherosclerosis risk in communities study

Objective: To develop protocols to photograph and evaluate retinal vascular abnormalities in the Atherosclerosis Risk in Communities (ARIC) Study; to test reproducibility of the grading system; and to explore the relationship of these microvascular changes with blood pressure. Design: Population-based, cross-sectional study. Participants: Among 4 examination centers, 11,114 participants (48-73 years of age) at their third triennial examination, after excluding persons with diabetes from this analysis. Methods: One eye of each participant was photographed by technicians with n onmydriatic fundus cameras. Reading center graders evaluated focal arteriol ar narrowing, arteriovenous (AV) nicking, and retinopathy by examining slid es on a light box and measured diameters of all vessels in a zone surroundi ng the optic disc on enhanced digitized images. To gauge generalized narrow ing, vessel diameters were combined into central arteriolar and venular equ ivalents with formulas adjusting for branching, and the ratio of equivalent s (AAI ratio) was calculated. Main Outcome Measures Retinal vascular abnormalities, mean arteriolar blood pressure (MABP). Results: Among 11,114 participants, photographs were obtained of 99%, with quality sufficient to perform retinal evaluations in 81%. In the 9040 subje cts with usable photographs, A/V ratio (lower Values indicate generalized a rteriolar narrowing) ranged from 0.57 to 1.22 (median = 0.84, interquartile range = 0,10), focal arteriolar narrowing was found in 7%, AV nicking in 6 %, and retinopathy in 4%. Because of attrition of subjects and limitation o f methods, prevalence of abnormality was likely underestimated. Controlling for gender, race, age, and smoking status, these retinal changes were asso ciated with higher brood pressure. For every 10-mmHg increase in MABP, A/V ratio decreased by 0.02 unit (P < 0.0001), focal arteriolar narrowing had a n odds ratio (OR) of 2.00 (95% confidence interval [CI] = 1.87-2.14), AV ni cking had an OR of 1.25 (95% CI = 1.16-1,34), and retinopathy had an OR of 1,25 (95% CI = 1.15-1.37). For any degree of generalized narrowing, individ uals with focal narrowing had MABP approximately 8 mmHg higher than those w ithout (P < 0.0001). Masked replicate assessment of a sample found the foll owing reproducibility: for A/V ratio, correlation coefficient = 0.79 and me dian absolute difference = 0.03; for focal arteriolar narrowing, kappa = 0. 45; for AV nicking, kappa = 0.61; and for retinopathy, kappa = 0.89. Conclusion: Protocols have been developed for nonmydriatic fundus photograp hy and for evaluation of retinal vascular abnormalities. Several microvascu lar changes were significantly associated with higher blood pressure; follo w-up will show whether these are predictive of later cerebrovascular or car diovascular disease independently of other known risk factors.