Sudden loss of vision in one eye in a parent or grandparent: why an eye stroke is an emergency
Mum says the sight in her left eye went dark, and it does not hurt. That is an emergency, not an eye-test matter for next week. Here is why it is treated like a stroke, which other causes cannot wait either, and what to do in the next ten minutes.
Call 999 or go to a hospital emergency department now if…
I see parents and grandparents for squint, cataract and everyday eye problems, so one family can keep one eye doctor. Family eye care Where I practise
- Painless sudden loss of sight in one eye, or a dark curtain over part of it, means call 999 or go to a hospital emergency department now. Do not wait for it to clear and do not wait for a clinic to open.
- A blocked artery in the retina is called retinal artery occlusion. The American Heart Association scientific statement describes central retinal artery occlusion as a form of acute ischaemic stroke and a medical emergency.
- Note the time the sight went. Treatment decisions depend on how long ago it started, and MedlinePlus puts the window for the treatments it lists at 2 to 4 hours.
- Vision that goes dark for minutes and then returns is a warning sign, not a relief. Go the same day, because the NHS says to get help even when stroke symptoms stop.
- A parent over 50 with headache, scalp tenderness or jaw pain when chewing, plus any change in sight, needs the same-day eye and medical assessment that giant cell arteritis calls for.
Your mother says the sight in her left eye has gone dark, as if a shutter came down. It does not hurt. She wants to lie down and see how it is in the morning. Please do not. Painless sudden loss of sight in one eye, or a dark curtain over part of it, is an emergency. Call 999 or go to the emergency department of a hospital now, note the time it started, and do not wait for it to clear.
This page explains why it is treated like a stroke, which other eye problems share the same urgency, and what to do in the next ten minutes. It is written for adults and for the grown-up children who get the phone call.
What should I do right now if my parent's sight goes in one eye?
Three things, in this order.
- Call 999, or take your parent to the emergency department of a hospital. The NHS stroke page advises against driving yourself to A&E, because the person who answers 999 will tell you what to do.
- Note the time the sight went, or the last time your parent knew it was normal. Write it down.
- Do not wait for it to clear, and do not book the next free eye appointment. Take the list of medicines and the glasses.
The action: if you are reading this with a parent beside you who has just lost sight in one eye, stop reading and make the call.
Why is a blocked artery in the eye treated like a stroke?
Because the American Heart Association says it is one. Its scientific statement on central retinal artery occlusion (Mac Grory and colleagues, Stroke 2021) calls it a form of acute ischaemic stroke that causes severe visual loss and is a warning of further brain and heart-vessel events. Its conclusion is plain: acute central retinal artery occlusion is a medical emergency, and care systems should send it to emergency medical attention.
MedlinePlus describes the same problem as a blockage in one of the small arteries that carry blood to the retina, the light-sensing layer at the back of the eye. It causes sudden blurring or loss of vision in all of one eye, or in part of it, and the loss is painless.
A blood clot in the eye may be a warning sign of clots elsewhere, and a clot in the brain may cause a stroke. The action: treat painless sudden sight loss in one eye as a stroke until a doctor says otherwise.
Why does the time it started matter?
Treatment depends on it. The American Heart Association statement says treatment with an intravenous clot-dissolving medicine may be effective, and also says the evidence is limited and good trials are still needed. MedlinePlus says the treatments it lists have to be given within 2 to 4 hours of the start of symptoms to help, and that their benefit has not been proven. It also warns that people with a blocked retinal artery may not get their vision back.
No page can tell you which treatment suits your parent. That is for the hospital team, and they can only decide if they know how long ago it started. The action: write the time down and say it to the first person you meet.
What if the sight goes dark for a few minutes and then comes back?
It is a warning sign, so go the same day. MedlinePlus says a retinal artery blockage may last only a few seconds or minutes, or it may be permanent. The NHS says stroke symptoms can stop after a short time, so you may think you are fine, and that you should get medical help straight away even so. Its TIA page says to call 999 even if the symptoms disappear while you wait for the ambulance.
A brief spell of darkness in one eye, like a curtain going down and up again, can be the first warning of something larger. The relief of it clearing is the moment people stop acting. The action: if it has cleared, still go to the emergency department today and tell them exactly what happened.
What other causes of sudden sight loss cannot wait?
Three others, and only an examination tells them apart. That is why this page gives one action for all of them.
- A blocked vein in the retina (retinal vein occlusion) can also cause sudden blurring in one eye. It is a same-day problem too.
- A retinal tear or detachment. MedlinePlus lists bright flashes, new floaters, blurred vision and a shadow or curtain across the side vision, usually without pain, and says it needs attention within 24 hours of the first symptoms. The full picture is on sudden floaters and flashes in a parent: when it means an eye doctor today.
- Giant cell arteritis, covered next, in people over 50.
If the problem is double vision rather than missing sight, a parent suddenly sees double: which signs mean hospital today sets out which signs mean hospital. The action: do not try to work out the cause at home.
Why do headache, scalp tenderness and jaw pain with a vision change matter?
They point to giant cell arteritis, inflammation of the arteries at the temples. The American Academy of Ophthalmology says it usually affects people over 50 and lists severe headaches, scalp tenderness around the temples, jaw cramps especially when chewing, and sudden vision problems. It says blindness generally happens first in one eye but can follow in the other if it is not treated, and that it is extremely important to be checked by an ophthalmologist right away.
The NHS says it is serious and needs urgent treatment, that vision problems call for a same-day appointment with an eye specialist at a hospital eye department, and that steroid treatment is started before the diagnosis is confirmed because of the risk to sight. The Academy adds that any vision already lost may be permanent. The action: a parent over 50 with these symptoms and any change in sight goes to hospital today. Headache and jaw pain on their own, with normal sight, still need a doctor the same day.
What happens at the hospital?
The team looks at the eye and at the whole person. MedlinePlus lists an examination of the retina after dilating the pupil, a check of the sight and of the side vision, blood pressure, and blood tests including cholesterol and the erythrocyte sedimentation rate. Tests for the source of a clot may include a heart tracing, an echocardiogram, a heart monitor and an ultrasound of the neck arteries.
The American Heart Association statement says people with this problem should have urgent screening and treatment of vascular risk factors. So a visit that began with one eye can end with a plan for blood pressure, diabetes, cholesterol or heart rhythm. The action: bring the medicine list and tell the team about any diabetes, high blood pressure or irregular heartbeat.
What if the sight loss is slow, in both eyes, or old?
Slow changes over months, such as gradual blurring from cataract or glaucoma, are not emergencies in the same way and belong in an eye examination in the coming days to weeks. The line is how it arrived. Sudden, in one eye, painless, a curtain or a blackout: emergency. A gradual drift: book an eye check, and mention it. If you cannot tell whether it was sudden, treat it as sudden. The action: when in doubt, go.
- The sight in one eye goes dark, blurred or missing, and it does not hurt.
- A dark curtain or shadow covers part of the sight in one eye.
- The sight goes dark for a few minutes and then comes back.
- There is also face drooping, arm weakness, slurred speech, double vision or a severe headache.
- A parent over 50 has headache, scalp tenderness or jaw pain when chewing, with any change in vision.
Common questions
Why is sudden loss of sight in one eye treated like a stroke?
Should I call 999 even if there is no pain?
What if the sight comes back within a few minutes?
Is it a stroke in the brain or a problem in the eye?
Is there a treatment for an eye stroke?
What else causes sudden sight loss in one eye?
What are the signs of giant cell arteritis?
Should I drive my parent to hospital myself?
- American Heart Association · Management of central retinal artery occlusion: a scientific statement (Mac Grory et al., Stroke 2021) · pubmed.ncbi.nlm.nih.gov
- MedlinePlus · Retinal artery occlusion · medlineplus.gov
- MedlinePlus · Retinal detachment · medlineplus.gov
- American Academy of Ophthalmology · What is giant cell arteritis? · www.aao.org
- NHS · Temporal arteritis (giant cell arteritis) · www.nhs.uk
- NHS · Symptoms of a stroke · www.nhs.uk
- NHS · Transient ischaemic attack (TIA) · www.nhs.uk