How does hypertension affect the eyes?
High blood pressure, or hypertension, not only raises the risk of heart disease and stroke but can also harm your vision. Over time, it can damage the blood vessels in the retina, the light-sensitive tissue at the back of the eye, as well as the nerves that transmit visual signals to the brain.
The eye is the only organ in the body where changes in blood vessels from high blood pressure can be seen directly. This is why high blood pressure, or hypertension, is sometimes first detected during routine eye exams.
In the United States:
- Nearly 50% of adults have high blood pressure (about 120 million people).
- About one-third of those with high blood pressure don’t realize it.
- Only about one-quarter of those with high blood pressure have it under control.
Understanding hypertension and eye complications can help you make informed health decisions. The longer you have uncontrolled blood pressure, the greater the risk of damage to your eyes. The chance of vision problems increases if you also have diabetes or high cholesterol or if you smoke.
Managing hypertension is key to avoiding the complications of high blood pressure in the eyes. These complications include:
- Damage to blood vessels (hypertensive retinopathy) – If blood circulation doesn't reach the retina, it might result in blurry vision or even partial to complete vision loss. People with diabetes and high blood pressure are more likely to have this issue.
- Fluid accumulation under the retina (choroidopathy) – Accumulation of fluid underneath the retina can cause warped, blurred vision and scarring.
- Optic nerve damage (optic neuropathy) – Poor blood circulation can injure the cells of the optic nerve, which carries signals from the eyes to the brain, potentially causing vision loss.
- Increased risk of certain eye conditions – Hypertension increases the chance of developing eye conditions such as glaucoma and macular degeneration.
What is hypertension?
Hypertension is the medical term for chronically high blood pressure. It occurs when the force of the blood flowing through the body's blood vessels is consistently too high. The high pressure of the blood flow can damage the arteries that supply the organs and tissues of the body.
Primary hypertension, also known as essential hypertension, is the most common form. It is not caused by another disease. Secondary hypertension is from other underlying conditions.
Pressure measurements appear as two digits with a dividing line. Blood pressure checks measure the force of the blood flow when it is pumped from the heart (systolic pressure) and when the heart is filling with blood again (diastolic pressure).
According to the American Heart Association:
- Normal blood pressure – Less than 120/80 mmHg
- Raised blood pressure – 120-129 systolic / below 80 diastolic
- Stage 1 hypertension – 130-139 systolic OR 80-89 diastolic
- Stage 2 hypertension – 140+ systolic OR 90+ diastolic
- Severe hypertension – 180+ systolic OR 129+ diastolic (contact your doctor)
- Hypertensive emergency – Above 180 systolic OR above 120 diastolic with additional symptoms. Call 911 if your blood pressure is in this range and you experience:
- Chest pain
- Changes in vision
- Shortness of breath
- Difficulty speaking
- Back pain
- Numbness
- Weakness
Common eye conditions linked to hypertension
High blood pressure can be detected in the eyes. Some signs of hypertension in the retina include:
- Bleeding (retinal hemorrhages)
- Deposits (exudates)
- Zig-zagged blood vessels
- Swollen blood vessels
If the optic discs, where the optic nerve connects to the retina, appear swollen, it is a condition called papilledema. This is a sign of a “hypertensive emergency” and urgent treatment is needed.
Hypertensive retinopathy
Hypertensive retinopathy is damage to the retina because of chronically high blood pressure. The high pressure can cause physical changes to blood vessels in the retina. Your doctor can see these changes during an eye exam. These include narrowing, twisting, nicking and swelling. Leaked fluids, proteins or fat deposits, as well as swelling around the center of the retina (the macula) can occur in later stages. The stages of hypertensive retinopathy are usually described as:
- Vasoconstrictive – Blood vessels narrow to protect the retina from high pressure.
- Sclerotic – Vessel walls thicken and become rigid.
- Exudative – The protective barrier breaks down, allowing blood and fluid to leak into the retina.
Many people with hypertensive retinopathy do not have symptoms until the condition has progressed to later stages. These symptoms could include:
- Dim or blurry vision
- Double vision
- Dim vision
- Headaches
The small blood vessels in the retina closely resemble those in the brain in both their structure and function. Studies have found that signs of hypertensive retinopathy are linked to a higher likelihood of experiencing a stroke.
Hypertensive choroidopathy
Hypertensive choroidopathy is damage in the blood vessel layer beneath the retina caused by high blood pressure. This can cause fluid to accumulate underneath the retina because of leakage from the blood vessels. It’s seen more often in younger patients who experience a sudden, severe spike in blood pressure.
Hypertensive optic neuropathy
Chronic high blood pressure can injure the optic nerve. This is the nerve that transmits light signals from the retina to the brain. When blood flow is reduced, it can damage the nerve fibers and visual signals can no longer be relayed properly.
This may lead to blurred vision, and in serious cases, it can even cause permanent vision loss. Your doctor can check for any swelling in the optic nerve or other related issues.
Retinal vein occlusion
High blood pressure can increase the risk of a condition called retinal vein occlusion (RVO), which is a blockage in the vein that carries blood away from the retina. This blockage can happen for a few reasons, such as:
- Pressure on the vein
- Slow blood flow
- A blood clot
The blockage can either be in the central or a branch vein. Symptoms of RVO may not be noticeable unless there are complications. If symptoms are noticed, they usually affect just one eye and include blurry vision, pain and seeing floaters.
Retinal artery occlusion
Arteries carry oxygen and nutrients to the tissues of the body. A retinal artery occlusion (RAO) occurs when a buildup of cholesterol or a blood clot restricts or blocks blood to the retina in one eye. It causes sudden and painless vision loss. The location of the blockage and whether it’s a central or branch RAO determine how severe the symptoms are.
People who have an RAO are at an increased risk of having a stroke. The risk is particularly high during the first four weeks following an RAO.
Transient ischemic attack
High blood pressure increases your risk of having a transient ischemic attack (TIA) or stroke. A TIA is a brief interruption of blood flow to the brain. Typically, the blockage either breaks apart or dissolves on its own, with symptoms generally lasting no longer than five minutes. Symptoms include:
- Vision loss in one or both eyes
- Numbness
- Dizziness
- Headache
Although a TIA does not result in lasting damage, it serves as a “warning stroke” indicating the potential for a more severe stroke in the future. If you have symptoms indicating a TIA, seek medical care immediately, even if the symptoms go away quickly.
Stroke
High blood pressure can increase the chances of having a stroke. A person has a stroke if a blood vessel supplying the brain is either obstructed by a clot or breaks open. When this occurs, a section of the brain (or the optic nerve) is deprived of essential blood and oxygen, leading to cell death. A stroke can damage several areas that affect vision, including the:
- Occipital lobe – An occipital lobe stroke can damage the area of the brain that processes vision.
- Optic nerve – Blocked blood flow to the optic nerve can cause damage to nerve fibers, leading to vision loss.
Someone with a recent retinal artery occlusion will be monitored closely as they are at higher risk for a stroke.
READ MORE: A guide to vision changes that can occur after a stroke
Diabetic eye complications
If you have diabetes, managing your blood pressure is critical to avoiding retinal damage. This is because high blood pressure speeds up the development and progression of diabetic retinopathy (DR). This condition damages the blood vessels of the retina. It usually does not have symptoms until the later stages, when blood vessels in the retina begin to bleed.
DR can lead to other serious eye complications, including diabetic macular edema. This is swelling in the center part of your retina (called the macula), resulting in blurry, warped vision.
Glaucoma
Some research has found an association between blood pressure and eye pressure, also known as intraocular pressure (IOP). High IOP is a major risk factor for glaucoma, a condition where damage to the optic nerve gradually leads to vision loss. However, the relationship between blood pressure and IOP is not direct, so controlling one does not automatically control the other or remove glaucoma risk.
Studies suggest that people with high blood pressure have a higher chance of developing glaucoma, and very high blood pressure can be harmful if you already have glaucoma. On the other hand, blood pressure that drops too low, especially at night in people taking blood pressure medication, can reduce blood flow to the optic nerve and may contribute to damage over time.
Because of this, anyone who has glaucoma or is at risk for it should make sure both their eye doctor and primary care doctor know about their eye condition and all medications, so they can work together to keep blood pressure and eye pressure in a safe range.
Age-related macular degeneration
Hypertension can raise the risk of developing age-related macular degeneration (AMD). This condition occurs due to deterioration of the macula, the area of the eye responsible for clear, direct vision. AMD causes a distortion of central vision. Making lifestyle adjustments, like effectively managing high blood pressure, may help slow the advancement of dry AMD.
Cataracts
A cataract is a clouding of the eye’s natural lens. It results in hazy and dim vision. Studies have found that high blood pressure is one of the contributors to an increased risk of certain types of cataracts. Once symptoms begin affecting daily life, surgery is required to remove the cataract.
Hypertensive emergency and papilledema
A hypertensive emergency (also called malignant hypertension) is a sudden, dangerous rise in blood pressure, typically exceeding 180/120 mmHg. It can result in damage to the eyes and other organs. It is a medical emergency and requires hospital admission.
A sign of a hypertensive emergency is papilledema. This is swelling of the optic nerve head (also called the optic disc). This swelling is caused by a dangerous rise in the pressure inside the skull (intracranial pressure). Other signs in the eye include deposits and blood leaking from the blood vessels.
Risk factors and demographics
If you have high blood pressure in addition to other health conditions, your risk of developing an eye disease can increase. For example, high blood pressure is a significant risk factor that accelerates the development and progression of diabetic retinopathy.
What causes high blood pressure?
Heredity and lifestyle can both contribute to high blood pressure. These factors include:
- Eating a high-salt diet or an unhealthy diet
- Living an inactive lifestyle
- Being age 55 or older
- Using alcohol or tobacco
- Having a family history of hypertension
High blood pressure symptoms can go unnoticed until severe damage has occurred to the eyes and body. This is why it’s important to have routine physical exams where your vital signs are checked. This is especially true if you’ve been diagnosed with cardiovascular disease. Routine eye exams help monitor your eye health and check for signs of hypertension and other serious conditions.
Preventative measures and treatments
Two important ways to care for your eyes are by controlling your blood pressure and scheduling routine eye exams.
Comprehensive eye exams
Comprehensive dilated eye exams and eye imaging tests like optical coherence tomography angiography (OCT or OCTA), color retinal photographs and fluorescein angiography (FA) are extremely important for people with hypertension. An eye doctor can observe detailed changes in the tiny blood vessels of the eye, which can provide indications of uncontrolled blood pressure. Early detection is crucial for preventing serious damage and vision loss.
An eye doctor may ask you to come in more than once a year to have a dilated eye exam with maintenance eye imaging tests.
Lifestyle changes
Making healthy choices in your daily life can help manage your blood pressure and protect your eye health. Your doctor may recommend that you:
- Limit salt intake
- Eat a nutritious diet
- Maintain a healthy weight
- Stop smoking
- Limit alcohol consumption
- Manage stress
Following these lifestyle changes in combination with taking any prescribed medications is crucial for lowering your risk of hypertension-related complications.
The role of diet and exercise
Eating a balanced diet is a key strategy for managing blood pressure. This includes eating nutritious whole foods like fruits, vegetables, beans, lean proteins and legumes. Foods high in omega-3 fatty acids and vegetables such as spinach and kale can provide key nutrients for your eyes.
Regular physical activity is also essential. Studies show that exercising 150 minutes per week greatly improves overall health and helps control blood pressure.
Medical treatments
If making healthy changes to your daily habits isn't enough to reduce or manage your high blood pressure, your doctor might recommend blood pressure medications. Before choosing which medications to prescribe, your doctor will factor in how these drugs might affect any other health problems you have, such as heart conditions or kidney problems. More than one drug may be prescribed.
Common high blood pressure medicines include:
- ACE (angiotensin-converting enzyme) inhibitors – Keep blood vessels from narrowing too much.
- ARBs (angiotensin II receptor blockers) – Keep blood vessels from narrowing too much.
- Calcium channel blockers – Help blood vessels relax and dilate.
- Diuretics – Often combined with other medicines to help remove excess fluid and salt.
If you experience unwanted effects from your blood pressure medications, discuss these concerns with your doctor. They may need to adjust your dosage or switch you to a different medication.
How often should I see an eye doctor if I have high blood pressure?
If you have high blood pressure, you should have a dilated eye exam at least once a year or as directed by your eye doctor. Annual comprehensive eye exams along with eye imaging tests can help monitor hypertension and eye complications.
You may be surprised by what your eye doctor can tell about your heart health. Changes in blood vessels from heart disease or hypertension can be detected during an eye exam.
Early detection is critical. The longer high blood pressure goes untreated, the more damage it can do to your body. This can result in a greater risk of vision loss and the development of other serious conditions. If you notice any type of sudden vision loss, disturbance or persistent eye pain, it’s important to see an eye doctor immediately.
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