Sudden loss of vision in one eye: when it is an emergency

It usually happens without warning. You are reading and you can no longer see out of one eye, or you see as if through a dark veil. No pain, no redness. Sometimes it lasts a few minutes and then everything returns to normal, and the temptation is to forget about it.

It is precisely in these cases that specialists ask people to behave as they would faced with a stroke. A sudden, painless loss of vision in one eye can be the sign that an artery of the retina has closed, an event that the most recent reviews regard as the equivalent of a stroke of the brain¹. The same applies to blurred vision in one eye that appears suddenly and has no obvious explanation.

In this article

1. The eye stroke: central retinal artery occlusion
2. Why you go to a stroke centre
3. When vision returns: amaurosis fugax
4. Over 50: giant cell arteritis
5. The other causes to recognise at once
6. Frequently asked questions
7. Sources

The eye stroke: central retinal artery occlusion

The retina receives blood mainly from one small vessel, the central retinal artery, which enters the eye together with the optic nerve. When it closes, vision drops suddenly, in one eye only and usually without pain¹. For this reason the American Heart Association, in a 2021 scientific statement, defines it as a medical emergency and asks that emergency systems recognise it and direct it at once to urgent care².

The diagnosis is made by examining the back of the eye, with the help of photographs of the retina and OCT, a test that shows its layers¹. What can be done afterwards is still a subject of research. There is no therapy accepted by everyone, and traditional treatments, such as massaging the eye or drawing off a little fluid from the eye (paracentesis), have shown no benefit and should not be used¹.

Hopes centre on thrombolysis, the clot-dissolving medicines used in stroke of the brain: recent reviews suggest a possible effect if given intravenously within 4.5 hours of the loss of vision, or into an artery within 6 hours, and randomised trials are under way to get a clear answer^1,2.

For the reader the point is not the therapy, which is for the doctors, but time: windows of a few hours are easily lost by waiting for vision to return on its own.

Why you go to a stroke centre

A closed artery of the retina is not only a problem of the eye. A 2020 meta-analysis pooled the studies in which people with a retinal arterial occlusion had had a brain MRI within 7 days: a recent cerebral ischaemia was present in 30% of those with a central artery occlusion and in 25% of those with a branch occlusion³. In many cases it caused no neurological symptoms: silent ischaemias involved 22% of people with central artery occlusion³.

A 2018 review stresses that the risk of stroke is highest in the first days after the loss of vision. For this reason guidelines recommend an urgent MRI of the brain and an examination of the vessels, and ask eye specialists to send these people at once to a stroke centre, without wasting time on other tests⁴. Risk factors for vascular disease must also be sought and treated quickly². And for someone with the symptom, the most useful thing is to call the emergency services, so as to be taken directly to a hospital with a stroke centre¹.

When vision returns: amaurosis fugax

If vision darkens in one eye and then returns within minutes, we speak of transient monocular vision loss, or amaurosis fugax. It has many causes, but most often it is due to a temporary lack of blood to the retina: it can herald permanent loss of vision or a stroke, and for this reason must be assessed urgently⁶. In the 2020 meta-analysis, almost 12 people in 100 with this problem already had a recent cerebral ischaemia on MRI³.

The UK National Health Service (NHS) too lists, among the symptoms of stroke, blurred or lost vision in one or both eyes, and recalls that symptoms can pass quickly: to those who have had them in the last 24 hours it nevertheless advises asking for help at once¹⁰. In younger people amaurosis fugax is often benign, but the assessment must in any case be adapted to each case⁶. We discuss the other causes of hazy vision, more or less urgent, in Sudden blurred vision.

Over 50: giant cell arteritis

In older people there is a cause not to be forgotten: giant cell arteritis, an inflammation of the large arteries, the most common vasculitis after the age of 50⁷. A 2026 review reports that it leads to a loss of vision in about 18% of cases, and that this loss can be avoided if the disease is recognised, investigated and treated early⁷. Treatment with corticosteroids is effective, although almost half of people have a relapse⁷.

The typical signs are headache and visual disturbances, up to loss of vision; in blood tests the markers of inflammation are high in over 9 people in 10⁸. The diagnosis is confirmed with a biopsy of the temporal artery, while ultrasound and MRI of the vessels help to support it⁸. For this reason, faced with a sudden drop in vision in an older person, doctors look for this disease too⁶.

The other causes to recognise at once

A 2026 review that proposes to doctors a pathway in five steps recalls that acute glaucoma attack, retinal detachment and optic neuritis must also be recognised immediately, as well as retinal artery occlusion and giant cell arteritis⁹. The first two questions of that pathway are simple: which eye is affected, and whether there is pain⁹. We have described the symptoms of retinal detachment and the difference between open-angle and angle-closure glaucoma in dedicated articles.

Frequently asked questions

What is an eye stroke?

It is the name given to occlusion of an artery of the retina: vision drops suddenly, in one eye and usually without pain. Reviews regard it as the equivalent of a stroke of the brain and ask that it be treated as such^1,2.

If vision returns after a few minutes, do you need to go to the emergency department?

Yes. A transient loss of vision in one eye can herald a permanent loss or a stroke, and the risk of stroke is highest in the first days^4,6. The UK National Health Service asks to call the emergency services even when the symptoms have passed¹⁰.

Is vision lost through occlusion of a retinal artery recovered?

Sometimes, in part. Without thrombolysis, in the 2025 meta-analysis about 11 people in 100 recovered from the severe vision loss; with intravenous thrombolysis within 4.5 hours, about 29 in 100⁵. These are results to be confirmed with randomised trials, and there is still no therapy accepted by everyone^1,5.

A sudden loss of vision in one eye is one of the few cases in which an eye problem is dealt with by calling the number you would call for a stroke. The studies of recent years repeat it from several sides: the brain can be involved even when it gives no signs³, the risk is concentrated in the first days⁴, and the therapies under study seem to give better results the earlier you arrive⁵.