An eye scan may reveal signs of atrial fibrillation years before doctors detect the irregular heart rhythm, according to a study involving nearly 90,000 people.
Researchers from Moorfields Eye Hospital and University College London found that people with atrial fibrillation had changes in specific layers of the retina, the light-sensitive tissue at the back of the eye. Some of the same changes were also found in people who had not yet developed the condition but went on to develop it later.
The discovery came from looking closely at the eye rather than the heart. Because the retina contains tiny blood vessels and nerve cells that can be viewed directly, researchers have been investigating whether it can provide clues about diseases affecting other parts of the body.
The Retina Changed in People with Atrial Fibrillation
The researchers analysed retinal scans from two large groups. One included 50,651 people from the AlzEye study, while the other included 39,013 people from the UK Biobank who did not have atrial fibrillation when their eye images were taken.
They compared the thickness of different retinal layers and examined the tiny blood vessels visible in the scans.
Several retinal measurements differed in people who already had atrial fibrillation. One of the clearest differences involved the macular ganglion cell-inner plexiform layer, or mGCIPL, a layer containing nerve cells that help transmit visual information towards the brain.
People with AF tended to have a thinner mGCIPL.
That finding became more interesting when the researchers looked at people who were initially free of the heart rhythm disorder.
The Same Eye Changes Appeared Before AF Was Diagnosed
During an average follow-up of four years in the UK Biobank group, 838 people developed atrial fibrillation.
The researchers found that people with a thinner mGCIPL were more likely to develop AF later. After accounting for factors including demographics, health and lifestyle, each standard-deviation decrease in the layer's thickness was associated with a 27% higher risk of subsequently developing atrial fibrillation.
The retinal scan, in other words, was showing a difference before the heart condition had been diagnosed.
That is particularly interesting because atrial fibrillation can be difficult to catch. The abnormal rhythm can come and go, and some people have no obvious symptoms. A person could therefore have a normal heart rhythm during a routine check even though episodes of AF occur at other times.
Why Would the Eye Reflect a Heart Problem?
The researchers do not yet know exactly why these retinal changes are associated with atrial fibrillation.
One possibility is that changes in circulation linked to AF may affect the retina's delicate nerve cells and blood vessels. Because these structures can be examined without surgery, the eye could provide a rare opportunity to observe subtle changes associated with cardiovascular disease.
The retina is already attracting attention for this reason. Researchers have increasingly been studying whether information contained in retinal images can reveal signs of conditions beyond eye disease.
But the new study does not show that retinal thinning causes atrial fibrillation, nor does it mean an eye scan can diagnose AF on its own.
An Eye Scan Would Not Replace a Heart Test
Atrial fibrillation is currently confirmed by recording the heart's electrical activity, usually with an electrocardiogram, or ECG.
Retinal imaging could have a different role. If future research confirms these findings, an eye scan might eventually help identify people who deserve closer monitoring for AF, particularly those who have no symptoms.
That could matter because untreated atrial fibrillation can increase the risk of blood clots and stroke.
The researchers still need to determine whether retinal measurements can reliably predict AF in different populations and whether using them in everyday healthcare actually leads to earlier diagnosis.
For now, the most striking part of the study is the timing. In some people, the first clue that their heart rhythm was heading towards atrial fibrillation may have appeared not in a heart tracing, but in the thin layer of tissue at the back of the eye.
