High blood pressure and the eyes: what the doctor sees

Key takeaways

High blood pressure can damage the small blood vessels of the retina (hypertensive retinopathy), and in the slow form it usually causes no symptoms, so feeling fine tells you very little.
The doctor sees the changes by looking at the back of the eye, usually with the pupil widened: narrowed arteries, small bleeds, leaks, swelling and, in the most severe form, a swollen optic nerve head.
A new blur that stays, in someone with high blood pressure, is a reason for an eye examination within days, and a mention to the family doctor.
Sudden painless loss of sight in one eye is an emergency today. High blood pressure is a risk factor for both retinal artery and retinal vein blockage. A very high reading with a headache or blurred vision means the emergency department.
The sources give no fixed interval for repeat dilated checks. Ask the family doctor whether the back of the eye has been looked at, and never stop or change a blood-pressure medicine because of how the eyes look.

Your father takes a tablet for his blood pressure and says his eyes are fine. Your mother has never had hers measured and has found the newspaper a little blurry lately. Both of you want to know the same thing: does high blood pressure reach the eyes? It does, and most of the time it does so quietly. This page explains what the eye doctor looks for at the back of the eye, which changes need a visit this week, and which need hospital today.

It does not advise on medicines and it sets no blood-pressure target. The family doctor does that. If your parent also has diabetes, the eye checks overlap, and our page on diabetes in the family and eye checks sets out that schedule.

What does high blood pressure do to the eyes?

It damages the small blood vessels of the retina, the light-sensing layer at the back of the eye. That damage is called hypertensive retinopathy. The Merck Manual says high blood pressure thickens the walls of the small retinal vessels, which reduces blood flow, so patches of the retina can be damaged. It adds that even mild high blood pressure may do this if it goes untreated for years.

The Merck Manual says the amount of retinal damage tends to match the damage in other organs that high blood pressure affects, such as the brain, heart and kidneys. The NHS names the brain, kidneys and eyes among the places that extra strain on blood vessels can harm.

The action: if a parent has high blood pressure, treat the eyes as one more organ the blood-pressure care is protecting, and ask the family doctor whether the back of the eye has been looked at.

Will my parent notice anything wrong with their eyes?

Usually not. The NHS says high blood pressure does not usually cause symptoms, and the American Academy of Ophthalmology's EyeWiki says many people with the slow, long-term form of retinopathy have no symptoms at all. Some do report poorer vision, and the Merck Manual says that as the condition progresses, blood can leak into the retina and cause a gradual loss of vision, especially if the macula (the centre of the retina) is affected.

So a parent who says "my eyes are fine" has told you very little. Only an examination shows the retina, and only a check shows the pressure.

The action: do not use how the eyes feel as the test. Use the blood-pressure reading and the eye examination.

What does the doctor look for at the back of the eye?

The doctor looks at the retinal vessels and the retina around them with a light and a lens. The Merck Manual says that using an ophthalmoscope, doctors can see the typical appearance of the retina in people with high blood pressure. EyeWiki says the diagnosis rests on this look at the back of the eye, usually with the pupil widened (a dilated fundus examination), together with the high blood pressure itself.

EyeWiki lists what can be seen:

Narrowed and twisted small arteries.
Small haemorrhages (bleeds), including flame-shaped ones.
Leaks called hard exudates, and pale patches called cotton-wool spots.
Swelling of the retina, and in the most severe form swelling of the optic nerve head (papilloedema).
Long-standing changes in the artery walls, such as where an artery crosses a vein.

You do not need to remember the names. EyeWiki also says the chronic changes in the artery walls do not go away once they are there, which is the reason to find out early and keep the pressure under the family doctor's care.

Which changes need an eye doctor this week, not at the next routine visit?

Any change in the sight of someone with high blood pressure that is new and does not clear: things looking gradually blurrier, dimmer or less clear in one or both eyes. These are not an emergency in the way the next section is, but they are a reason to book an eye examination now and to tell the family doctor too.

EyeWiki notes that decreased vision is often reported in the slow form, and the Merck Manual describes a gradual loss. The Merck Manual says the main goal is long-term blood-pressure control, so the eye visit and the family doctor visit belong together.

The action: new blurring that stays is a visit within days, with a note from you of when it began and whether one eye or both.

Which changes are an emergency today?

Two situations. The first is sudden sight loss in one eye. The second is very high blood pressure together with blurred vision or a bad headache.

High blood pressure is a risk factor for both blockages that cause sudden sight loss. EyeWiki says it predisposes people to blockage of the retinal artery and of the retinal vein. MedlinePlus lists it among the conditions linked to most cases of artery blockage, which causes sudden blurring or loss of vision in all or part of one eye, and says treatments must be given within 2 to 4 hours after symptoms begin.

Moorfields Eye Hospital calls blockage of a retinal vein a common cause of sudden, painless reduction in vision in older people, and lists high blood pressure among its risk factors.

Our page on sudden loss of vision in one eye and why an eye stroke is an emergency says what to do in the first ten minutes: call 999 or go to a hospital emergency department, and write down the time it started. If a dark curtain or a burst of floaters is the problem, our page on sudden floaters and flashes covers it.

For very high pressure, the Malaysian hypertension guideline (5th edition, 2018) defines severe hypertension as a persistent systolic pressure above 180 mmHg and/or diastolic above 110 mmHg. It says such patients may have headache, dizziness or lethargy, and that a hypertensive emergency is severe elevation with new or worsening damage to an organ, which can happen at lower readings if the pressure has risen fast.

Those patients are admitted for immediate treatment. EyeWiki says patients in a hypertensive crisis should go to an emergency department. I do not set a number for your parent. Your family doctor's plan tells you which reading to act on. The action: a very high reading with a headache or blurred vision means the emergency department, not a booking.

Who in the family should have the back of the eye checked, and when?

Anyone with diagnosed high blood pressure should have the back of the eye looked at as part of the first assessment, and again as the eye doctor and family doctor agree. The Malaysian guideline lists a fundus examination (a look at the back of the eye) among the physical examinations at initial assessment, and lists retinal haemorrhages, exudates and papilloedema as signs of target organ damage.

The sources give no fixed interval for repeat dilated checks, so none is given here. EyeWiki says follow-up depends on how much retinopathy there is and how the blood pressure is doing, and recommends close coordination between the ophthalmologist and the primary care doctor. For a parent who also has diabetes, the diabetes schedule applies and usually covers the same examination. See the diabetes eye-check page for those intervals.

Which relatives are most likely to need it? The NHS lists a family history of high blood pressure, older age, being overweight, smoking, heavy drinking and long-term stress as risks. The Malaysian guideline says every adult above 18 should have their blood pressure checked at least once as part of annual health screening, and more often with a family history or obesity, because a high number of Malaysians are undiagnosed. A relative who has never had a reading is the person to get one, before anyone worries about the eyes.

The action: ask each parent two things at the next visit, when was my blood pressure last measured, and has anyone looked at the back of my eyes.

How does the eye check fit with the family doctor's blood-pressure care?

The family doctor owns the blood pressure, and the eye doctor reports what the eye shows. The Merck Manual says the main goal is long-term lowering of blood pressure, with immediate treatment needed only rarely, when pressure is severe and life-threatening. EyeWiki says most acute retinal changes improve with blood-pressure control, though the artery changes and narrowing can persist and damage to the macula or the optic nerve can leave lasting sight loss.

Do not let anyone stop or change a tablet because the eye looks fine, or because it looks bad. That is a decision for the doctor who prescribes it. Moorfields adds a useful point for the vein blockage: treating risk factors such as high blood pressure lowers the chance of a further blockage, and without treatment there is a high risk of it returning. Bring the eye doctor's letter to the family doctor, and the family doctor's current blood-pressure readings to the eye doctor.

The action: keep one list on the phone, with the date of the last blood-pressure reading, the date of the last eye examination, and the names of the tablets. Show it at every visit.

Do not wait for the next appointment if your parent…

Loses sight suddenly in one eye, whether all of it or part, with or without pain. Call 999 or go to a hospital emergency department now and note the time it started.
Has a very high blood-pressure reading together with blurred vision or a bad headache. Go to the emergency department.
Sees a dark curtain or shadow across the sight, many new floaters or flashes of light. Same-day eye care.
Has blurring that is new, does not clear, and comes with known high blood pressure. Book an eye examination within days and tell the family doctor.

Common questions

Can high blood pressure damage my eyes without me knowing?

Yes. The NHS says high blood pressure does not usually cause symptoms, and the American Academy of Ophthalmology's EyeWiki says many people with the long-term form of retinopathy have none. Only a blood-pressure check and an examination of the back of the eye show it.

What is hypertensive retinopathy?

It is damage to the small blood vessels of the retina caused by high blood pressure. The Merck Manual says high blood pressure thickens the walls of those vessels and reduces blood flow, and that even mild high blood pressure may do this if untreated for years.

What does the eye doctor look for at the back of the eye?

EyeWiki lists narrowed and twisted small arteries, small bleeds, hard exudates, cotton-wool spots, retinal swelling and, in the most severe form, a swollen optic nerve head. The Merck Manual says doctors see the typical appearance with an ophthalmoscope.

Which eye problems linked to high blood pressure are emergencies?

Sudden loss of sight in one eye, from a blocked retinal artery or vein. EyeWiki says high blood pressure predisposes to both. MedlinePlus says treatment for an artery blockage must be given within 2 to 4 hours after symptoms begin, so call 999 or go to a hospital at once.

My father has high blood pressure and blurred vision. Is that an emergency?

It depends on the reading and how it began. The Malaysian hypertension guideline defines severe hypertension as above 180 systolic and/or 110 diastolic and lists headache among its symptoms. A very high reading with blurred vision or headache means the emergency department. New blurring with a controlled reading means an eye examination within days.

How often should someone with high blood pressure have a dilated eye check?

The sources used here give no fixed interval. The Malaysian guideline includes a look at the back of the eye in the first assessment, and EyeWiki says follow-up depends on the degree of retinopathy and the blood-pressure control. Ask the family doctor and the eye doctor, and follow the diabetes schedule if diabetes is also present.

Should I tell my mother to change her blood-pressure tablet if her eyes look affected?

No. That decision belongs to the doctor who prescribes it. The Merck Manual says the main goal is long-term lowering of blood pressure. Bring the eye findings to the family doctor, and bring the latest readings to the eye doctor.

References

American Academy of Ophthalmology · EyeWiki: Hypertensive retinopathy · eyewiki.aao.org
Merck Manual (consumer version) · Hypertensive retinopathy · www.merckmanuals.com
MedlinePlus · Retinal artery occlusion · medlineplus.gov
Moorfields Eye Hospital NHS Foundation Trust · Retinal vein occlusion · moorfields.nhs.uk
NHS · High blood pressure (hypertension) · www.nhs.uk
Ministry of Health Malaysia, Malaysian Society of Hypertension, Academy of Medicine of Malaysia · Clinical Practice Guidelines: Management of Hypertension, 5th edition (2018) · mymahtas2.moh.gov.my

By Dr Chan Li Yen. General information only. It does not replace a consultation. If you are worried about your child's eyes or vision, please see an eye doctor.

High blood pressure and the eyes: what the doctor sees at the back of the eye, and which changes need a visit this week