What Is Central Retinal Artery Occlusion?

Patients ask after suddenly losing the vision in one eye without any pain, sometimes waking with it or having it happen in an instant, and being told it was an artery blockage or a stroke in the eye. The lack of pain is confusing, and so is being sent for heart and brain testing when the problem seemed to be only in the eye. They want to understand why it happened, whether the vision can return, and why it is treated so urgently.

The retina is nerve tissue that needs a steady flow of oxygen-rich blood, delivered mainly by the central retinal artery. In CRAO, that artery is suddenly blocked, usually by an embolus, a clot or a fragment of cholesterol plaque, that traveled from the carotid arteries in the neck or from the heart. With the blood supply cut off, the retina stops functioning almost immediately, which is why vision fails suddenly and painlessly.

Retinal cells cannot tolerate a lack of blood flow for long, so the opportunity to restore circulation and rescue vision is narrow, often just hours. That is why CRAO is treated exactly like a brain stroke. And because the blockage came from the same circulation that feeds the brain, the danger is not only to the eye: the next event could be a disabling brain stroke, which makes urgent, whole-body evaluation critical.

In central retinal artery occlusion, the main retinal artery is blocked, cutting off the whole retina; a branch retinal artery occlusion blocks a smaller vessel and spares part of the vision. Sometimes a warning precedes it: amaurosis fugax, a transient loss of vision in one eye that goes dark and then returns, which signals that a permanent occlusion or a brain stroke may be near.

The usual cause is an embolus from carotid artery disease or from the heart, including atrial fibrillation. The risk factors are the risk factors for stroke and heart attack: high blood pressure, diabetes, high cholesterol, smoking, and older age. In adults over about fifty, giant cell arteritis, an inflammation of medium and large arteries, is a crucial cause to exclude, particularly when there is headache, scalp tenderness, jaw pain with chewing, unexplained weight loss, or fever, because it can rapidly take the second eye and is treated emergently with steroids.

Because CRAO shares its plumbing and risk profile with brain stroke, it is classified as a stroke equivalent. National guidance calls for immediate emergency care with brain imaging, evaluation of the carotid arteries and heart, and prompt treatment to prevent the next, potentially devastating, vascular event, even in the many cases where the affected eye's vision cannot be fully recovered.

CRAO is serious and urgent in every case. Sudden, painless loss of vision in one eye demands an emergency response, call 911 or go to a stroke-capable ER without delay.

It is an even greater emergency when accompanied by signs of brain stroke: one-sided weakness or numbness, facial droop, trouble speaking or understanding, severe headache, or loss of balance. In older adults, symptoms such as new headache, tender temples or scalp, jaw pain when chewing, and fever raise concern for giant cell arteritis, which must be treated immediately to protect the fellow eye. Any brief episode of vision blacking out and returning should also be treated as an urgent warning.

An ophthalmologist confirms CRAO on a dilated retinal exam by finding a pale, whitened retina from the loss of blood flow, often with a cherry-red spot at the fovea, narrowed arteries, and sometimes a visible embolus. But because this is a stroke, evaluation extends far beyond the eye. The emergency team performs an urgent stroke workup: brain imaging, imaging of the carotid arteries, cardiac evaluation for embolic sources such as atrial fibrillation, and assessment of blood pressure, blood sugar, and cholesterol. In patients over fifty, ESR and CRP blood tests are checked right away to screen for giant cell arteritis, which may require a temporal artery biopsy and immediate high-dose steroids while results are pending.

No treatment reliably reverses CRAO, which is precisely why getting to emergency care within hours is so important. In patients who present very early, some stroke centers consider clot-dissolving therapy (thrombolysis), the same treatment used for brain stroke, and ophthalmologists may attempt maneuvers to try to move the clot or lower eye pressure. These interventions are time-sensitive and belong in a stroke-capable emergency setting.

The larger goal is preventing the next event. That means identifying and treating the source, managing carotid disease and the heart, starting antiplatelet or anticoagulant therapy when appropriate, and aggressively controlling blood pressure, cholesterol, and diabetes with your medical team. If giant cell arteritis is suspected, high-dose steroids are begun immediately to save the other eye. Ongoing care focuses on long-term stroke and cardiovascular risk reduction.

• Do not wait, rest, or sleep on it hoping vision returns, the retina is on a clock and delay can make blindness permanent.
• Do not drive yourself, call 911 to reach a stroke-capable emergency room quickly.
• Do not accept eye-only care, CRAO is a stroke and needs a full emergency workup of the brain, heart, and carotid arteries.
• Do not brush off a brief episode of one eye going dark and recovering, it can herald a full occlusion or a brain stroke.
• Do not assume it is migraine or fatigue, sudden painless vision loss in one eye is an emergency until proven otherwise.

If you suddenly lose vision in one eye without pain, do not book a routine appointment, call 911 or go straight to the nearest stroke-capable emergency room, anywhere in the Hanover area, because central retinal artery occlusion is treated as a stroke. After emergency evaluation and stabilization, May Eye Care Center can assist with follow-up eye care, but emergency treatment must come first and cannot wait.

Central retinal artery occlusion is a stroke of the eye that causes sudden, painless vision loss in one eye and warns of brain-stroke risk; it is a 911 emergency, go to a stroke-capable ER immediately rather than waiting.