• New research has identified a link between vascular complexity in the eye’s retina and the risk of having a myocardial infarction, or in other words, a heart attack.
• The discovery was made by using artificial intelligence and “deep learning” to process data representing a large group of individuals.
• Combined with new genetic insights, the researchers can accurately predict heart attacks when the model includes demographic data.

Soon, retinal scans may be able to predict heart attacks. New research has found that decreased complexity in the blood vessels at the back of the retina in the human eye is an early biomarker for myocardial infarction.

“For decades, I’ve always lectured that the eye is not just the window to the soul, but the window to the brain and the window to the body as well,” said ophthalmologist Dr. Howard R. Krauss, speaking to Medical News Today about the new research.

“AI [artificial intelligence] plus ‘deep learning’ is proving that to be the case,” he said.

Cardiologist Dr. Rigved Tadwalkar, who was not involved in the research, told MNT that the findings were interesting.

“[A]lthough we have known that examination of retinal vasculature can produce insights on cardiovascular health, this study contributes to the evidence base that characteristics of the retinal vasculature can be used for individual risk prediction for myocardial infarction,” he said.

“This [study] represents another tool in the toolbox to help determine who could potentially benefit from earlier preventative intervention [when it comes to heart attacks].”
— Dr. Rigved Tadwalkar

“The greatest appeal,” said Dr. Krauss, who was also not involved in the study, “is that the photography station may be remote to the clinician, and perhaps, someday, even accessible via a smartphone.”

The research was presented on June 12 at the European Society of Human Genetics.

Retinal scans and blood vessels

According to a press release, the project utilized data from the UK Biobank, which contains demographic, epidemiological, clinical, and genotyping data, as well as retinal images, for more than 500,000 individuals. Under demographic data, the data included individuals’ age, sex, smoking habits, systolic blood pressure, and body-mass index (BMI).

The researchers identified about 38,000 white-British participants, whose retinas had been scanned and who later had heart attacks. The biobank provided retinal fundus images and genotyping information for these individuals.

At the back of the retina, on either side where it connects to the optic nerve, are two large systems of blood vessels, or vasculature. In a healthy individual, each resembles a tree branch, with similarly complex fractal geometry.

For some people, however, this complexity is largely absent, and branching is greatly simplified.

In this research, an artificial intelligence (AI) and deep learning model revealed a connection between low retinal vascular complexity and coronary artery disease.

The power of AI

“The beauty of utilizing AI and deep learning is that as the database builds, one may learn of associations, and the predictive value of retinal evaluations, in ways which we may not even suspect today,” said Dr. Krauss.

Dr. Krauss added there are advantages of using AI and deep learning in such research.

“AI is capable of looking at a photograph and, with 97% accuracy, telling whether it’s a male or female. No ophthalmologist can look in the eye, or look at a photograph, and tell you if it’s male or female,” beyond guessing, he said.

The AI model was moderately successful when considering vascular density alone. However, Villaplana-Velasco described its accuracy as “significantly reduced when compared with a model that also included demographic data, and with established risk models.”

“Even when we just included age and sex to retinal vascular complexity, we found a significant improvement,” she said.

Specific genetic regions

A third factor improved the predictive power of the researchers’ model even further.

“Our genetic analysis showed,” said lead author and Ph.D. student Ana Villaplana-Velasco, “that four genetic regions associated with retinal vascular complexity have a role in MI-related biological processes.”

She said that her team was interested in further studying this link “by collaborating with other research groups focused on in-vitro experiments.”

“The findings make sense, in that a true association was seen between fractal dimension [complexity] and incident cardiovascular disease,” said Dr. Tadwalkar.

He noted that “the model also integrates [a polygenic] risk score, which can significantly improve precision on its own.”

Spotting signs of other diseases

Dr. Krauss said that the retina could hold clues to many systemic diseases.

“For over a hundred years, since the ophthalmoscope was invented, the retina has been used to diagnose a variety of systemic diseases in modern-day medicine. Once we now apply AI and deep learning networks, we’re able to see retinal changes before the ophthalmologist would necessarily see them,” he said.

“These changes are not exclusive for higher MI risk,” Villaplana-Velasco told MNT, adding that these findings could be applicable to other diseases.

“We believe that every condition might have a unique retinal vascular variations profile.”
— Ana Villaplana-Velasco, lead author

“[The findings are] certainly a step in the right direction and [provide] at least partial explanation,” said Dr. Tadwalkar. “However, we would need to see additional research reproducing the findings.”

Both Dr. Tadwalkar and Dr. Krauss expressed concern over the limited range of individuals represented in the data. Dr. Krauss pointed out a majority were “white U.K. residents and not gender stratified.”

“The data used in the study are inherently limited by the population studied,” said Dr. Tadwalkar.

“Future work should be focused on the reproduction of results in other cohorts and/or in larger numbers of patients, as this would not only validate the findings but also improve risk prediction,” he added.

Could the eyes predict cardiovascular risk?

Doctors consider a variety of factors to determine a person’s risk of experiencing cardiovascular events, including age, smoking history, and blood pressure. But changes to the blood vessels in the back of the eye may make for a more accurate prediction.

They say that the eyes are the window to the soul. But, according to a team of researchers, they may also be the window to the heart.

Previous research has identified a link between changes in the eye and hypertension in adults, and similar retinal changes and high blood pressure in children.

“The data that we have is very clear that at a very early age, in children 6 to 8 years old who are otherwise healthy, you can already see vascular alterations due to blood pressure levels that are on the high end of normal,” says Dr. Henner Hanssen, professor of preventive sports medicine and systems physiology at the University of Basel, Switzerland.

“We don’t know if this predicts worse outcomes when they become adults, but we have seen similar alterations in adults that are predictive of cardiovascular mortality and morbidity,” he continues.

Millions of blood vessel measurements

This study is the largest to look at the relationship between the eye and cardiovascular diseases and has produced the most dependable measurements. It appears in the American Heart Association’s HypertensionTrusted Source journal.

The study found that small blood vessels at the rear of the eye were affected by artery stiffness and increased blood pressure.

As lead author professor Alicia Rudnicka from London’s St. George’s University in the United Kingdom explains: “If what’s happening in the rest of the body is reflected in what’s happening at the back of the eye, what we see there could be a flag, taking retinal morphology assessment from being just a research tool to incorporating it into clinical practice.”

Almost 55,000 elderly or middle-aged people from the UK Biobank study formed the data set for the new research, and in total, the team had access to 3.5 million blood vessel sections.

An automated program examined digital images of each participants’ retinal blood vessels, providing the team with measurements relating to blood vessel diameter and curvature.

The retinal link to heart disease

Analysis of these found that greater curvature of the retinal arteries equated to higher pulse pressure, higher average artery pressure during a heartbeat, and higher systolic blood pressure, which is the pressure that occurs when the heart contracts.

This was not the only finding. The team also noticed a relationship between greater stiffness in artery walls, higher mean arterial pressure, and narrowing of the retinal blood vessels.

None of these retinal effects impact a person’s vision, but they “could potentially tell us very quickly whether you are on the road to cardiovascular disease,” according to Prof. Rudnicka.

“What we have now is one piece of the puzzle,” she adds.

“If we can link the retinal vessel measurements of the past to what happens to these people years later, this will tell us whether these vessel changes came before cardiovascular disease and go on to predict those who go on to have a cardiovascular event.”

Prof. Alicia Rudnicka

The team’s next study aims to determine whether these measurements can predict heart disease in the same person a decade later.

Cardiovascular disease is the leading cause of deathTrusted Source globally. Currently, experts estimateTrusted Source a person’s risk factor using a range of factors, including age, sex, blood cholesterol levels, and blood pressure.

Prof. Rudnicka’s future study results may determine whether the eye becomes part of that list.

• Credit: Medical News Today