Retinal Scans May Reveal Atrial Fibrillation, Large Study Suggests

A scan that takes a few seconds in an optometrist's office may carry information about the heart. That is the argument behind a new study from Josef Huemer, MD, and colleagues, published in PLOS Digital Health, which found that people with atrial fibrillation show measurable structural differences in the retina.

The work drew on more than 90,000 people in two independent cohorts. AlzEye was a retrospective set of 50,561 patients aged 40 and older, seen between 2008 and 2018. UK Biobank was a prospective cohort of 39,539 people aged 40 to 69, recruited between 2006 and 2010. Retinal layer thicknesses came from macular optical coherence tomography, and vascular measures came from color retinal photographs. Atrial fibrillation, or AF, was identified through patient reports and hospital admissions. Huemer is affiliated with the NIHR Moorfields Biomedical Research Centre and the Institute of Ophthalmology at University College London, and with the Department of Ophthalmology and Optometry at Kepler University Hospital in Linz, Austria.

The motivation is practical. AF is common, and its prevalence is expected to double again over the next two decades. It contributes to ischemic stroke, myocardial infarction, vascular dementia and death. Yet it is hard to catch, because it comes and goes and may not appear when an ECG is running. The authors note that AF episodes themselves do not map directly onto clotting-related outcomes. They describe AF as a thrombo-inflammatory condition closely tied to underlying vascular disease, and they argue that anticoagulants and treatments aimed at vascular disease could have substantial public health impact if diagnosis came earlier and reached more communities. Their reasoning for looking at the eye was that the retina shares structural and vascular features with the brain and heart.

In both cohorts, participants with AF were on average older than those without it. They were also more likely to be male, to have hypertension and diabetes, and, most strikingly, to have had a prior major adverse cardiovascular event.

In AlzEye, where AF prevalence was 11%, the condition was associated with a smaller retinal venular caliber and thinner layers across the macula: the retinal nerve fiber layer, the ganglion cell-inner plexiform layer, the inner nuclear layer and the photoreceptor layer. Fractal dimension, a measure of vessel branching complexity, was lower in the venules but higher in the arterioles of people with AF.

UK Biobank also showed a thinner macular ganglion cell-inner plexiform layer (mGCIPL) in people with AF. Of 39,013 participants free of AF at baseline, 1.3% developed it over a mean of 4.0 years. After adjusting for sociodemographic, clinical and lifestyle factors, each standard deviation drop in mGCIPL thickness was linked to a 27% higher hazard of AF.

The thinner inner nuclear layer was a new finding. The authors say mGCIPL thinning has a plausible connection to AF-related microvascular injury, but reduced inner nuclear layer thickness had not been described in this setting before.

The authors see potential for noninvasive retinal imaging to support early detection and risk stratification, and to offer an accessible way to study AF pathophysiology and assess end-organ damage. They point to the wide availability of retinal imaging in primary care optometry across developed countries as a reason to pursue it further.

Huemer said a notoriously hard-to-diagnose heart condition leaves visible traces in the retina that quick scans can capture. The next step is multimodal imaging to build stronger evidence for a causal link. Whether earlier detection actually improves patient outcomes, he said, is something future studies will have to establish.