A new study suggests that eye scans may be able to detect early signs of atrial fibrillation (AF), a heart condition that can increase the risk of stroke, years before a formal diagnosis. Researchers analyzed data from over 90,000 people and found that individuals with AF had distinct biological markers in their retina, the light-sensitive tissue in the eye responsible for converting light into visual signals. This discovery could offer a new, non-invasive method for identifying people at risk of AF before symptoms appear. Atrial fibrillation is a common heart condition that causes an irregular and often rapid heartbeat. It can be asymptomatic or intermittent, making it difficult to detect during standard heart tests like electrocardiograms (ECGs). In the UK, it is estimated that about 1.5 million people have AF, but many more may be undiagnosed. The condition itself is not directly life-threatening, but it can lead to the formation of blood clots, which can cause strokes if they travel to the brain. The study was conducted by researchers at Moorfields Eye Hospital NHS Foundation Trust and the UCL Institute of Ophthalmology. They examined data from 50,651 participants in the AlzEye study and 39,013 people from the UK Biobank. Among these, around 6,261 individuals had AF. The analysis found that those with AF had thinner retinal layers compared to those without the condition. Additionally, people who later developed AF had thinner retinal layers up to four years before they were diagnosed, suggesting that retinal changes might occur before the condition becomes apparent. One patient, John Brewer from Croydon, discovered he had AF during cataract surgery when doctors noticed an irregular heartbeat. He was given an ECG and medication to proceed with the surgery, and a cardiologist later confirmed the diagnosis. Mr. Brewer expressed that an early retinal scan during routine checkups could have identified the condition sooner, avoiding the distress of discovering it during surgery. Experts emphasize that while retinal scans would not replace ECGs for diagnosing AF, they could serve as a complementary tool. Siegfried Wagner from UCL noted that retinal imaging is non-invasive, quick, and easily accessible. If further research confirms these findings, routine eye exams might help identify individuals who could benefit from more detailed heart assessments, potentially allowing for earlier treatment to reduce stroke risk. The study has been published in the journal Plos Digital Health.