The eyes are the windows not only to the soul, but also to a person’s health, a new study says.

Premature aging of the retina could be a red flag for major diseases like diabetes or heart disease, researchers recently reported in the journal Communications Medicine.

They found that people had a higher risk of chronic disease if they had advanced aging of their retinas — the light-sensitive layer of cells that lines the back wall of the eye.

For the study, researchers trained an artificial intelligence (AI) model to estimate the wear-and-tear age of a person’s retina based on fundus images, which are photos of the eye’s back inner wall.

AI analysis of these photos could be used to help detect these diseases during regular check-ups, researchers said.

"Fundus images are non-invasive photos of the eye taken as part of regular health check-ups — so no additional work is needed," senior researcher Toru Nakazawa, a professor at Tohoku University in Japan, said in a news release. "Our model would be a nearly frictionless addition to a clinician's typical workflow."

For the new study, researchers trained the AI model to assess retinal age using more than 50,000 fundus images. A person’s retina can be older than their actual calendar age, if retinal aging is accelerated by unhealthy behaviors or disease.

The AI model became good at accurately predicting a person’s actual age based on their retina, but researchers found there was a larger gap between retinal age and calendar age for some people.

Analysis showed that people with diabetes, heart disease or a history of stroke tended to have a significantly larger gap between their retinal and calendar age. 

The retinas of these people appeared older than expected.

"We are already planning a study that follows a cohort of over 10,000 individuals with continuous three-year follow-up to examine whether retinal age-related signals are associated with the future development of cardiovascular and other systemic diseases," Nakazawa said.