Elsevier

Ophthalmology

Volume 106, Issue 12, 1 December 1999, Pages 2269-2280
Ophthalmology

Methods for evaluation of retinal microvascular abnormalities associated with hypertension/sclerosis in the atherosclerosis risk in communities study1,

https://doi.org/10.1016/S0161-6420(99)90525-0Get rights and content

Abstract

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 nonmydriatic fundus cameras. Reading center graders evaluated focal arteriolar narrowing, arteriovenous (AV) nicking, and retinopathy by examining slides on a light box and measured diameters of all vessels in a zone surrounding the optic disc on enhanced digitized images. To gauge generalized narrowing, vessel diameters were combined into central arteriolar and venular equivalents with formulas adjusting for branching, and the ratio of equivalents (A/V 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 subjects with usable photographs, A/V ratio (lower values indicate generalized arteriolar 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 of methods, prevalence of abnormality was likely underestimated. Controlling for gender, race, age, and smoking status, these retinal changes were associated with higher blood pressure. For every 10-mmHg increase in MABP, A/V ratio decreased by 0.02 unit (P < 0.0001), focal arteriolar narrowing had an odds ratio (OR) of 2.00 (95% confidence interval [CI] = 1.87–2.14), AV nicking 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, individuals with focal narrowing had MABP approximately 8 mmHg higher than those without (P < 0.0001). Masked replicate assessment of a sample found the following reproducibility: for A/V ratio, correlation coefficient = 0.79 and median 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 photography and for evaluation of retinal vascular abnormalities. Several microvascular changes were significantly associated with higher blood pressure; follow-up will show whether these are predictive of later cerebrovascular or cardiovascular disease independently of other known risk factors.

Section snippets

Study design and population

The ARIC Study (sponsored by the National Heart, Lung, and Blood Institute) is an epidemiologic examination of the major factors contributing to the occurrence of cardiovascular disease in middle-aged adults in the United States. It has two main objectives:

  • 1.

    To investigate factors associated with both atherosclerosis and incidence of clinical cardiovascular disease.

  • 2.

    To measure occurrence of coronary heart disease and relate its trends to community levels of risk factors, medical care, and

Methods

Following is a summary of the ARIC Study methods for taking retinal photographs and evaluating them for vascular abnormalities (complete procotols are provided in the ARIC Manual of Operations16).

Photography of participants

Among the 11,114 participants who had photography attempted, photographs were obtained of 1 eye in 99% (Table 1). In these 10,954 subjects with photographs (Table 2), 88% could be measured on the image processor for generalized arteriolar narrowing, 85% could be graded on the light box for focal vascular abnormalities, and 83% could be assessed for both (using the number of subjects in whom photography was tried as the denominator reduced the yield of usable photographs to 81%). Generally, a

Discussion

Using the image processor protocol to measure diameter of the retinal vessels, we found a normal distribution of A/V ratio in the ARIC Study population. Lower A/V ratio, indicating greater degree of generalized arteriolar narrowing, was strongly and monotonically associated with higher blood pressure (for MABP, that was 10 mmHg higher, A/V ratio was 0.02 lower). Using the light box protocol for grading focal arteriolar narrowing, AV nicking, and retinopathy, we found such focal abnormalities in

Acknowledgements

The authors thank Elizabeth Ehrhardt, MD, Robert Sperduto, MD, and the ARIC Retinal Reading Center photography and grading staff (Barbara Esser, Christine Fulmer, Cynthia Hurtenbach, Kelly Kewley, Kathleen Miner, Michael Neider, and Kurt Osterby) for their collaboration in the development of these methods.

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  • Cited by (0)

    Supported by The National Heart, Lung, and Blood Institute of the National Institutes of Health, Contract Numbers NO1-HC-35125, N01-HC-35126, N01-HC-55015, N01-HC-55016, N01-HC-55018, N01-HC-55019, N01-HC-55020, N01-HC-55021, and N01-HC-55022.

    1

    The authors have no proprietary interest in the equipment and techniques described in this article.

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