If one eye suddenly goes dark like a curtain being pulled down, treat it as a stroke and go to the emergency room the same day, even if it clears up in a few minutes

In a real emergency, call 911 first, then read this.

Cost

Free. The emergency evaluation and vessel tests take half a day to a day.

What you get

The American Heart Association's 2021 scientific statement on central retinal artery occlusion (the main vessel at the back of the eye being blocked) says: "acute central retinal artery occlusion is an emergency." The care system should recognize it as an emergency and set priorities accordingly. The longer the blood supply is cut, the less retina can still be saved. The Oxford EXPRESS study looked at two kinds of patients: minor stroke, and brain ischemia whose symptoms clear up on their own (medically called transient ischemic attack). After these patients were switched to same-day evaluation and same-day start of treatment, the share having another stroke within 90 days fell from 10.3% (32/310) to 2.1% (6/281). The summary of the same scientific statement also states that central retinal artery occlusion is a form of acute ischemic stroke, and a warning sign of cerebrovascular and cardiovascular events to come. The UK National Health Service (NHS) lists "blurred or lost vision in one or both eyes" as a stroke symptom, and states that you should seek medical help at once even if the symptoms stop after a while. If you had stroke symptoms in the past 24 hours and they have now stopped, you should likewise call the emergency number

Notes

Graded B because EXPRESS was not a randomized trial. It compared the same population before and after a change in practice, and other conditions may also have changed between the two periods, which can't be separated out. A sudden blackout in the eye that recovers in a few minutes is easily dismissed as "tiredness" or "low blood sugar." The NHS states that even if the symptoms stop on their own, you should seek medical help at once. Among the EXPRESS patients not treated the same day, 10.3% had another stroke within 90 days. If sight in one eye is suddenly lost, even without pain or redness, take it seriously. Don't wait for the eye clinic the next day. Go straight to the emergency room of a hospital with a stroke center.

Evidence grade

B : Supported by research but without a precise number, or based on small or single studies.

Sources

1. Mac Grory B, Schrag M, Biousse V, et al. (2021). Management of Central Retinal Artery Occlusion: A Scientific Statement From the American Heart Association. Stroke, 52(6), e282-e294: "Central retinal artery occlusion (CRAO) is a form of acute ischemic stroke that causes severe visual loss and is a harbinger of further cerebrovascular and cardiovascular events". https://doi.org/10.1161/STR.0000000000000366
2. NHS. Symptoms of a stroke: "blurred vision or loss of sight in 1 or both eyes" "Symptoms of a stroke can sometimes stop after a short time, so you may think you're OK. Even if this happens, get medical help straight away" "you've had signs of a stroke within the last 24 hours even if they've now stopped". https://www.nhs.uk/conditions/stroke/symptoms/
3. Rothwell PM, Giles MF, Chandratheva A, et al. (2007). Effect of urgent treatment of transient ischaemic attack and minor stroke on early recurrent stroke (EXPRESS study): a prospective population-based sequential comparison. Lancet, 370(9596), 1432-1442. https://doi.org/10.1016/S0140-6736(07)61448-2

Translated from the Chinese original. Original book, section 13, tip 5. Content may be out of date and rules differ by place. When you actually deal with an agency, a doctor or a court, follow what local officials, doctors and lawyers tell you. Disclaimer