Your eye doctor can help keep an eye on your heart. Risk factors for heart disease like high blood pressure, diabetes and high cholesterol can be detected early during a comprehensive eye exam. In fact, your eye doctor may be the first to detect if you’re at risk for a heart attack or stroke.

Certain markers in the arteries and veins of the retina can provide eye doctors with important clues about what is happening in the small blood vessels of the brain and heart.

Due to age and other risk factors such as high blood pressure and high cholesterol, arteries may narrow, harden and become clogged with deposits called “plaque.” This is known as atherosclerosis. It can affect blood vessels in the heart, brain and entire body, including small arteries supplying blood to the retina and optic nerve.

Small pieces of cholesterol plaque can sometimes break away from the carotid artery, a major blood vessel that branches off the aorta (from the heart) and supplies blood to the brain and eyes. These plaque deposits can travel to the arteries of the eye, making them visible during a dilated eye exam. 

If these pieces of plaque reach the brain, they can cause a stroke. If your eye doctor spots plaque deposits, you will be sent to your primary care doctor, or to get an imaging study done. 

Eye conditions that reveal artery blockage, narrowing and hardening include:

Amaurosis fugax 

Amaurosis fugax can result from blockage of the internal carotid artery. It is a temporary loss of vision in one eye that can last up to 30 minutes. This is a warning sign that a stroke may happen. 

Retinal artery occlusions

The most common cause of a retinal artery occlusion is an embolism, which is a blockage of an artery by a circulating blood clot. An embolism can travel from the heart or blood vessel and lodge in the eye. This can be visible during an eye exam. 

The three most common types of blockages are due to cholesterol and calcium (from the carotid arteries that send blood from the heart to the brain) and blood clots from the valves of the heart. Your eye doctor can see the blockages as a white or orange blockage in your eye’s blood vessels.

A retinal artery occlusion is sometimes referred to as an “eye stroke” and can result in sudden, painless vision loss and difficulty seeing. 

A 2015 study found that previously undiagnosed vascular (relating to blood vessels) risk factors were found in 78% of all central retinal artery occlusion patients. A 2017 study found that after a retinal artery occlusion, there was a high risk of a vascular event (such as a stroke) occurring within one month. 

Central retinal artery occlusion (CRAO)

Retinal vein occlusions 

Another type of “eye stroke,” a retinal vein occlusion (RVO) can indicate high cholesterol and high blood pressure. Retinal vein occlusions are the result of blood clots, narrow blood vessels or stiffened arteries that compress veins at junctions where they cross each other.

Sudden or gradual vision loss and blurry vision in part or all of one eye can result. An eye doctor may see signs of “arteriovenous nicking” — or constriction of the vein — where an artery crosses above it. 

A 2016 South Korean National Health Insurance Service study analyzing over one million people found that the development of retinal vein occlusion was associated with a higher risk of a heart attack. 

A 2019 meta-analysis delivered additional bad news. The analysis of 15 studies and nearly half a million people found that patients with RVO have an increased risk of cardiovascular events and death. 

A branch retinal vein occlusion (BRVO) can develop from a blood clot.

Xanthelasma

A possible sign of high cholesterol is the presence of yellow bumps or raised areas around the eyes and near the nose. These deposits, called xanthelasma, are the result of cholesterol that has built up under the skin. 

While they do not affect your vision, they may indicate heart disease. Nearly half of individuals who have xanthelasma have high cholesterol.

Arcus senilis / Corneal arcus

This condition is caused by fatty substances and cholesterol that create a light gray or blue ring around the edge of the cornea.

It is common in middle or older age, and is referred to as “arcus senilis” in this age group. But, it can be an indicator of high cholesterol in children or young adults (when it may be called juvenile corneal arcus). 

Men younger than 40 with corneal arcus have an increased risk of death from coronary artery or cardiovascular disease compared with men who do not have it. 

If an eye doctor finds the presence of corneal arcus in a patient younger than 40, a cholesterol screening with a primary care doctor will be recommended.

Appearance of arcus senilis (corneal arcus).

It’s common for blood pressure to rise and fall during the day, but when blood pressure is consistently higher than normal, it’s called hypertension. 

During a dilated eye exam, an eye doctor may suspect high blood pressure if they notice the following:

• Damaged arteries in the eyes

• Arteries in the eyes that are significantly smaller than the veins, or veins that are much bigger and bulging

Eye conditions that may indicate high blood pressure include:

Hypertensive optic neuropathy

Changes to the appearance of the optic nerve from high blood pressure are visible during a dilated eye exam. Optic neuropathy, or damage to the optic nerve, can result if blood flow to the optic nerve is blocked. Since the optic nerve carries signals from the retina to the brain, damage to its nerve fibers can cause vision loss.

Hypertensive retinopathy

Chronically high blood pressure can cause physical changes to blood vessels such as narrowing, “zig-zagging,” nicking and swelling. These changes are clearly visible during an eye exam. High blood pressure can eventually lead to bleeding in the eye, blurred vision or vision loss. 

According to the NIH, there has been significant evidence that hypertensive retinopathy can be a predictor of disease or death due to organ damage from uncontrolled blood pressure.

Hypertensive chorioretinopathy/choroidopathy

Damage to the eyes’ blood vessels from high blood pressure can lead to the development of leaky blood vessels. This can lead to fluid building up underneath the retina (choroidopathy), which can be visible during a comprehensive eye exam. It can lead to distorted vision and retinal scarring. 

Your eye doctor will recommend that you speak to a primary care doctor regarding high blood pressure if these conditions are detected during your eye exam.

SEE RELATED: High blood pressure: Hypertension's effect on eye health

Your eye doctor may be able to take an image of your eye to help detect heart disease earlier than ever before, according to the American Academy of Ophthalmology. Considering that heart disease is the leading cause of death in the world, diagnosing and treating heart disease early could help to prevent a heart attack or stroke.

Decreased blood flow due to heart disease can manifest in the retina, which receives nourishment from the central retinal artery. If the supply of blood to the retina is blocked or reduced, it is called “ischemia” and it results in retinal cell death.

When a retinal cell dies, it leaves a mark on the retina that is visible using technology called an OCT scan. By counting the number of marks left by dead retinal cells, eye doctors can detect whether a person may be at risk for a heart attack or stroke.

Aortic regurgitation is a condition that occurs when the heart's aortic valve does not close tightly. As a result, there is a large difference between a person’s systolic (when the heart beats) and diastolic (when the heart rests) blood pressure. Although it is rare, the pupils can dilate and constrict in sync with the heartbeat. This is referred to as Landolfi’s sign.

In 2018, Google’s health technology branch, Verily, published a study showing that an algorithm could use an individual’s retinal scans (current and historical) to predict their risk of cardiovascular disease.

The algorithm is programmed to identify which patients may suffer from a cardiac event in the next five years. The accuracy rate was 70%, similar to the blood tests that are currently used. The benefit is that this risk assessment can be done during an appointment at the doctor’s office, rather than having to wait for results from a blood lab.

Comprehensive dilated eye exams play an important role in maintaining both eye health and heart health. In fact, an eye doctor may see markers for heart disease before any other symptoms are present. A comprehensive eye exam can detect life-threatening risk factors for heart disease and start a critical conversation about heart health.