High blood pressure, also known as hypertension, is a common condition that can lead to serious health complications if left untreated. It has been nicknamed the “silent killer” because often there are no obvious symptoms. About 1 in 3 American adults have high blood pressure (1). Given the dangers of uncontrolled high blood pressure, early detection and treatment are critical. But how can you tell if someone has high blood pressure just by looking at their eyes?
What is high blood pressure?
Blood pressure is a measurement of the force exerted on the walls of the arteries as blood flows through the circulatory system. It is recorded as two numbers:
– Systolic pressure – the pressure in the arteries when the heart contracts
– Diastolic pressure – the pressure in the arteries when the heart relaxes between beats
Blood pressure is measured in millimeters of mercury (mm Hg) and is represented with the systolic pressure listed first, followed by the diastolic pressure. For example, a blood pressure reading of 120/80 mm Hg means a systolic pressure of 120 and a diastolic pressure of 80.
High blood pressure is defined as having a systolic pressure of 130 mm Hg or higher, or a diastolic pressure of 80 mm Hg or higher, on repeated checks over time (2). Normal blood pressure is below 120/80 mm Hg.
When blood pressure is elevated but not yet in the high range (systolic between 120-129 and diastolic under 80 mm Hg), it is called elevated blood pressure or prehypertension. Prehypertension increases the risk of developing high blood pressure if lifestyle modifications are not made (3).
How does high blood pressure affect the eyes?
High blood pressure can cause damage to blood vessels throughout the body, including the small blood vessels in the eyes. Over time, uncontrolled high blood pressure stresses the delicate blood vessels in the retina, the light-sensitive tissue at the back of the eye. This can lead to several characteristic changes in the eyes.
Some common eye problems caused by high blood pressure include:
Retinopathy
Retinopathy refers to damage to the retina from high blood pressure. The walls of the retinal blood vessels can become weakened and leak fluid or blood, or retinal blood vessels can become blocked. Retinopathy is a leading cause of blindness among adults (4).
There are two main types of retinopathy linked to high blood pressure:
– Hypertensive retinopathy – generalized retinal damage from chronic high blood pressure. This causes retina swelling, blockages, and bleeding.
– Retinal vein occlusion – a blockage of the retinal vein due to high blood pressure, cutting off blood flow out of the eye. This can cause vision loss.
Choroidopathy
The choroid is the layer of blood vessels and connective tissue between the retina and the white of the eye. Hypertension can disrupt blood flow to the choroid, leading to damage called choroidopathy. Symptoms include distorted or blurred vision.
Optic neuropathy
High blood pressure can injure the optic nerve, which transmits visual information from the retina to the brain. Damage to the optic nerve is called optic neuropathy, which can progress to permanent vision loss or blindness if not treated.
Optic disc swelling
The optic disc is where the optic nerve connects to the retina, and it can become swollen due to high blood pressure. Optic disc swelling, also called papilledema, occurs when excess fluid accumulates within or around the optic nerve as it exits the eye. Papilledema is considered an ophthalmological emergency as it can rapidly progress to permanent optic nerve damage and blindness.
Can you detect high blood pressure from examining the eyes?
Certain eye issues are strongly associated with high blood pressure and can serve as warning signs of possible hypertension. Looking closely at the eyes and being aware of the following signs can help identify individuals who need further screening for high blood pressure:
Retinal vascular changes
The retina contains tiny blood vessels that are directly observable during an eye exam using specialized instruments that allow a view inside the eye. Looking at the caliber (width), any variability in caliber, and any abnormalities of the retinal vessels can indicate high blood pressure:
– Arterial narrowing and venous dilatation – High blood pressure causes arteries in the retina to become narrowed and veins to dilate and enlarge. This distortion in vascular caliber is a hallmark sign of hypertension.
– Arteriovenous nicking – Where retinal arteries and veins cross, there is normally a gradual transition. Hypertension causes nicks or notches to develop at arteriovenous crossings, making the transition more abrupt.
– Retinal hemorrhages and microaneurysms – These spots of retinal bleeding and localized vessel bulges indicate severe retinopathy from chronically high blood pressure.
Optic disc swelling
Swelling of the optic disc is directly visible during an eye exam and is strongly associated with high blood pressure in the absence of other causes like infection or inflammation. The swollen disc takes on a fuzzy, hyperemic appearance.
Choroidal infarcts
These are patches of damage to the choroid layer of the eye that appear as well-defined pale areas during an eye exam. Choroidal infarcts, or scars, develop from poor blood supply and hypertension.
Are there limitations to judging blood pressure from the eyes?
While retinal vessel abnormalities and other ocular signs can be indicative of hypertension, there are some limitations:
– Mild high blood pressure may not produce any visible eye damage in the early stages. The eyes reflect late-stage or end-organ damage from chronically elevated blood pressure rather than early signs.
– Conditions other than high blood pressure can also affect the appearance of retinal blood vessels and the optic nerve. Eye exams alone cannot definitively diagnose hypertension.
– Objective documentation of subtle retinal changes requires high quality fundus photography and trained physicians. Subtle signs of hypertension may be missed on routine eye exams.
– Not all patients with hypertension develop retinal abnormalities. The lack of observable damage does not rule out high blood pressure.
– Some retinal arteriolar narrowing can occur naturally with aging and may not reflect disease.
Bottom line
While examining the back of the eye can sometimes reveal warning signs of high blood pressure, an eye exam is not sufficient to diagnose hypertension. However, noticeable changes like retinal arteriolar narrowing, optic disc swelling, and choroidal scarring should prompt referral for a medical workup of high blood pressure.
How are the eyes directly examined for signs of high blood pressure?
To thoroughly evaluate the eyes for manifestations of hypertension, an eye care provider uses specialized instruments and techniques to gain a close-up, magnified view of the retina at the back of the eye:
Pupil dilation
Drops are used to enlarge (dilate) the pupils, allowing more light into the eyes to achieve a clearer view of the retina.
Ophthalmoscopy
An ophthalmoscope shines a very bright light into the eye, enabling visualization of the retina, including the optic disc and retinal blood vessels.
Slit lamp exam
The slit lamp microscopically examines the front structures of the eye under high magnification and illumination. This can reveal changes to the optic nerve fibers as they exit the eye.
Fundus photography
Specialized fundus cameras take photographs of the retina to document vascular abnormalities and optic disc changes. This provides objective evidence that can be compared over time.
Optical coherence tomography (OCT)
OCT uses light waves to take cross-sectional images of the retina, revealing detailed structures, including thickness changes from swelling.
Fluorescein angiography
A fluorescent dye is injected into the arm. Retinal photos reveal how the dye circulates through the eye’s blood vessels. This highlights areas of leakage, blockage or disruption.
How are direct changes to eye structures related to high blood pressure measurements?
Certain retinal vascular signs, like arterial narrowing, correlate to measured blood pressure levels:
Mild hypertension
Early on in hypertension, the arteries and veins of the retina may appear normal, or there may be subtle asymmetry and very mild arterial narrowing.
Moderate hypertension
With moderately high blood pressure, retinal artery narrowing is more obvious on exam. The arteriovenous ratio decreases, meaning the veins look larger in caliber compared to the arteries.
Severe hypertension
In severe or longstanding high blood pressure, retina blood vessels exhibit marked narrowing of arteries and dilatation of veins. Retinal hemorrhages, microaneurysms and cotton wool spots indicative of advanced retinopathy may be visible.
Hypertensive crisis
A hypertensive crisis with blood pressures over 180/120 mm Hg can produce swelling of the optic nerve head and blurred disc margins as the optic disc swells. Retinal vessels may also appear segmented and disconnected.
How accurate is an eye exam for detecting high blood pressure?
Using ophthalmoscopy to visualize damage to retinal arterioles and venules can identify hypertension with moderate accuracy. Research studies have reported the following statistics on using retinal vessel examination to screen for high blood pressure:
– Sensitivity – 40-92%
– Specificity – 43-95%
– Positive predictive value – 46-90%
– Negative predictive value – 45-95% (5, 6)
This indicates there is a trade-off between accurately identifying people who have hypertension (sensitivity) and accurately identifying those who don’t have it (specificity). Focusing too much on one metric could produce more false negatives or false positives.
Overall, retinal vessel evaluation has acceptable accuracy for identifying individuals with likely hypertension who need definitive blood pressure measurement and treatment. However, accuracy depends greatly on the examiner’s skill and experience.
Can a routine eye exam detect high blood pressure?
A comprehensive dilated eye exam by an optometrist or ophthalmologist includes examination of the retina, which may reveal signs of hypertension. However, there are some limitations to relying on a routine eye exam to detect high blood pressure:
– The eye exam may focus more on visual acuity and eye health rather than subtle vascular changes that require close inspection. Mild retinal vessel abnormalities can be missed.
– The eye care provider is not measuring actual blood pressure or necessarily looking for hypertension. Their role is vision care rather than diagnosing medical conditions like high blood pressure.
– Documentation of retinal changes may be cursory. Subtle changes indicative of early hypertensive retinopathy likely won’t make it into the medical record communicated to the primary care physician.
– Patients may only see their eye doctor annually or less often, leading to delayed recognition of hypertension.
The takeaway
While a thorough eye exam can sometimes detect retinal changes from high blood pressure, it should not take the place of regularly monitoring your actual blood pressure. An eye care provider may alert you to possible hypertension but formal diagnosis requires blood pressure measurements over time by a qualified medical professional.
Should you get your eyes checked for high blood pressure?
Getting a dilated eye exam not only screens vision and eye health, but provides an additional way to check for signs of high blood pressure. It serves as part of the body’s surveillance system for this “silent killer.” Advantages of an eye exam include:
– It is non-invasive and easy to do annually.
– It allows direct visualization of blood vessels being damaged by hypertension.
– Eye doctors have the tools and expertise to examine the retina closely.
– It can detect high blood pressure that is not causing obvious symptoms and may be missed.
– Finding early signs of retinopathy motivates better compliance with blood pressure treatment.
Who should receive retinal screening?
The American Heart Association recommends a dilated eye exam to evaluate the retina for hypertensive changes in the following groups (7):
– Adults with hypertension
– People with family history of hypertension
– Individuals at high risk for heart disease and stroke
– Patients with diabetes, which commonly coincides with high blood pressure
– African Americans, who face higher rates of hypertension
– Older adults
Can you measure blood pressure directly from the eye?
New technologies are emerging that allow direct measurement of blood pressure by analyzing retinal blood vessels in the eye. Specialized retinal imaging and software can detect subtle changes in retinal vessel width with each heartbeat. This allows estimation of systemic blood pressure.
Examples of techniques under development include:
Dynamic vessel analysis
This analyzes subtle variations in artery and vein width over the cardiac cycle captured on video imaging of the retina. The arterial pulsations indicate pressures.
Ocular plethysmography
Uses a probe on the eye to trace tiny volume changes of retinal blood vessels with each pulse, which reflects blood pressure.
Tonometry
Involves gentle pressure on the outside of the eyeball to detect the pulse pressure from tiny movements of the flexible optic nerve head.
These technologies aim for non-contact, non-invasive, quick blood pressure assessment just using the eye. However, accuracy is still under study and not yet sufficient to replace traditional arm cuff blood pressure measurement. But the area is an exciting field to improve hypertension detection and monitoring.
The bottom line on examining eyes for high blood pressure
While the eyes can sometimes show signs of hypertension-related damage, direct blood pressure measurement is still required to definitively diagnose and monitor high blood pressure. An eye care provider may suspect hypertension based on a retinal exam but cannot acting as a treating physician.
However, the eyes do provide an important window into the effects of chronic high blood pressure on the body. People should get regular dilated eye exams not only to check vision but to screen for medical conditions like diabetes and hypertension that present threats to eye health. The visit is a chance to look for early warning signs that can prompt lifesaving treatment and prevent blindness.
New ocular imaging methods to directly estimate blood pressure also show promise for improved hypertension detection in the future. Overall, examining the eyes can provide valuable clues in the fight against the “silent killer” but should not replace other diagnostic practices.
References
1. https://www.cdc.gov/bloodpressure/facts.htm
2. https://www.heart.org/en/health-topics/high-blood-pressure/the-facts-about-high-blood-pressure
3. https://www.heart.org/en/health-topics/high-blood-pressure/understanding-blood-pressure-readings
4. https://www.cdc.gov/visionhealth/basics/ced/index.html
5. https://pubmed.ncbi.nlm.nih.gov/17921403/
6. https://pubmed.ncbi.nlm.nih.gov/29983398/
7. https://www.heart.org/en/health-topics/consumer-healthcare/what-is-cardiovascular-disease/retinal-screening-for-hypertensive-changes
