What can your eyes tell you about heart disease?

The eyes do more than allow us to see; they have something to say. In fact, an eye exam can reveal underlying health problems.

How is this possible? The arrangement of blood vessels at the back of the eye, known as the retina vasculature, is closely connected to the health of your heart. That means issues we see in the eye can be directly linked to health problems with the heart and the vessels in your body.

Most eye exams include an inspection of the outside and inside of the eye. To do this, your ophthalmologist will use an ophthalmoscope to examine things such as pupil reflexes, the lens of your eye, the retina and the optic nerve.

High blood pressure

High blood pressure, also known as hypertension, happens when the force of blood against an artery wall is too high. In the eye, high blood pressure can cause retinopathy, or damage to the eye’s main blood supply. This can lead to bleeding in the eye, blurred vision, swelling, blood clots, damage to the nerve or even stroke in the retina with complete loss of vision.

An eye specialist can look at the blood vessels in your eye and detect signs of high blood pressure or even diabetes — even without using a blood pressure cuff.

The ratio between the size of retinal arteries to veins is supposed to be approximately two to three. So, if the artery is a lot smaller than the vein, or the vein is a lot bigger and dilated, that may indicate high blood pressure or cardiovascular risk factors.

Sometimes, patients may not know they have high blood pressure — which rarely has physical symptoms, but can lead to heart disease and stroke — until they come in for an eye exam. I have had patients come in for a regular checkup, and I found some evidence of changes in the ratio or shape of retinal vessels or small blood clots in the eye. The clots were not affecting their vision, and the patients were discovered to have high blood pressure and high cholesterol.

Blocked arteries

Hypertension isn’t the only heart-related ailment that can be detected in the eye. If we see small emboli in the eye, they can be coming either from an arteriosclerotic plaque in the carotid artery, which is the main artery that brings blood to the head and neck, or they can come from emboli in the heart.

An arterial embolism occurs when an embolus has traveled through the arteries and become stuck in small vessels or organs like the brain or the retina. This can either restrict or block blood flow, which can result in tissue damage, a stroke, blindness or even death.

Diabetes

Diabetes also is an ailment that is commonly diagnosed through an eye exam. But because diabetes can have a slow onset, people may miss obvious clues.

In the eye, high blood sugar can bring about problems in the small blood vessels. If this occurs, a patient is at risk for developing diabetic retinopathy, which can lead to blindness and issues of the heart and kidneys. Diabetes also is linked to heart disease.

Going blind from diabetes or developing cardiac issues does not have to happen. A simple eye exam can help a patient catch it early and put them on the path to proper treatment.

Arthritis

Not only can heart problems be revealed through a routine eye exam; systemic inflammatory diseases that cause arthritis and inflammation in other parts of the body can also be detected. Many of these conditions can cause eye inflammation and can result in pain and redness and vision loss. Dry eye, for example, is commonly associated with these conditions. If severe and left untreated, it can cause damage to the cornea, the dome-shaped, clear surface of the eye.

Leveraging big data

The research into the eye-heart connection is increasing. Google and its health-tech subsidiary, Verily, published a study in 2018 in Nature Biomedical Engineering that showed the company’s machine-learning algorithm is able to successfully predict a patient’s risk for cardiovascular disease based on a scan of the backs of their eyes. The algorithm, which used 300,000 images of eyes, is designed to tell which patients are likely to suffer from a cardiac event in the next five years. It also had information about the patients’ age, smoking history, gender and history of high blood pressure. Its 70% accuracy rate is similar to the current blood test method that’s correct about 72% of the time. It won’t find the disease, but it can find risk factors that would be associated with heart failure.

Big data-fueled algorithms can be especially helpful in remote areas where access to eye specialists is limited, and can help ophthalmologists improve their diagnostic skills, algorithms and the care they provide patients. But I don’t think they will replace the traditional eye exam.

The eye of an experienced ophthalmologist can pick up pattern changes but cannot analyze numbers to the degree a computer does. But there is still clinical judgment that’s needed, especially when you have to put the history of the patient together and formulate a differential diagnosis and management plan.

So, the next time you are ready to skip your long-awaited eye appointment, it would be wise to remember you could be missing more than meets the eye.

Retinal specialist Dimitra Skondra, MD, PhD, is an Associate Professor of Ophthalmology and Visual Science at the University of Chicago Medicine.