Retinal microvascular structure and function in patients with risk factors of atherosclerosis and coronary artery disease
Introduction
The retinal circulation is unique as it allows a direct and non-invasive window to the health of the human circulation in vivo. Large epidemiologic studies have shown that retinal microvascular signs (e.g., arteriovenous nicking, focal arteriolar narrowing, and measurement of static retinal vascular calibre) provide information on risk of vascular complications, cardiac events and stroke in the general population [1], [2], [3], [4], [5], [6].
The mechanisms and pathways underlying these associations remain, however, unclear. Advances in retinal vascular imaging technology have allowed retinal microvascular function, a nitric oxide dependent phenomenon, to be evaluated in “real time” by non-invasive dynamic assessment of retinal vascular dilatation in response to diffuse luminance flicker light using the Dynamic Vessel Analyser (DVA) [7]. There are limited data on how static retinal microvascular signs are correlated with retinal microvascular endothelial function, particularly in subjects with or at risk for coronary heart disease [8]. Understanding the associations between static and dynamic retinal vascular markers may help in further developing a diagnostic tool capable of early detection of atherosclerosis, and assist in risk stratification of patients with cardiovascular disease.
To address these gaps, we sought to examine the feasibility of measuring retinal microvascular endothelial function using the DVA in patients with or at risk of coronary artery disease, and to study the inter-relationship between retinal vascular structure and function.
Section snippets
Study population and patient preparation
The study was approved by the Human Research Ethics Committee of Austin Health and written informed consent was obtained from all subjects. All participants (n = 258) underwent retinal photography, including static and dynamic assessment. The inclusion criteria for recruitment were that participants had to have at least two traditional cardiovascular risk factors and/or clinically evident coronary artery disease. Traditional cardiovascular risk factors included a history of hypertension,
Reproducibility and association between eyes
The characteristics of the study population are displayed in Table 1. ICC was 0.99 and 0.98 for baseline arteriolar and venular diameter respectively, and 0.82 and 0.79 for flicker-light induced retinal arteriolar and venular dilatation respectively. None of 13 baseline retinal arteriolar and venular diameter measurements were beyond the limits of agreement while at maximum dilatation, 1/13 of the arteriolar (FI–RAD), but not venular (FI–RVD), measurements were beyond the limits of agreement (
Discussion
In this study of patients with or at high risk of coronary artery disease, we investigated the reproducibility of retinal microvascular endothelial function assessment using the DVA and studied the inter-relationship between retinal vascular function and structure. The main findings are as follows. First, we showed that baseline and flicker light induced retinal arteriolar and venular dilatation, utilising the DVA, is reproducible. Second, we found modest to strong statistically significant
Financial disclosures
None.
Funding sources
Dr Al-Fiadh was supported by a co-funded Postgraduate Scholarship from the National Health and Medical Research Council (NHMRC) and National Heart Foundation of Australia (ID 567147). This work was supported in part by a Grant-in-Aid from the National Heart Foundation of Australia (G 08M 3781).
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2020, Microvascular ResearchCitation Excerpt :This notion is supported by various publications. One study demonstrated an inverse relationship between retinal artery dilation in response to FLIP and the arterial diameter of the measured segment (Al-Fiadh et al., 2014). The authors speculated that the greater dilation in smaller vessels was due to increased shear stress in smaller vessels.
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2018, Journal of Clinical LipidologyCitation Excerpt :The results from the 3 flicker periods were averaged and percent dilatation of the arteriole or venule from baseline (FIDart and FIDven, respectively) was calculated automatically using Imedos analysis software. Reproducibility of the method and the used measurement protocol has been demonstrated before.10 The authors report very good intraclass and intraobserver correlations (ICC 0.82), with 18% of the variability in measurements of FIDart due to errors in the measurement process and the observer.