When people think of strokes, they immediately think of an abnormality occurring in the brain. However, it can happen in the eyes too. This type of stroke is referred to as retinal artery occlusion.
A typical stroke affecting the brain can occur in one of two ways: ischemic or hemorrhagic. Both have the same end result—cell death—but occur differently. Hemorrhagic stroke occurs due to an aneurysm in the brain rupturing, causing blood to escape and decreased perfusion to the area of the brain affected. Ischemic stroke occurs due to the blockage or narrowing of the blood vessels supplying the brain with vital nutrients and oxygen—therefore, the affected area becomes starved of blood, leading to a stroke.
Ischemic strokes are more related to the eye. In the case of strokes, the blockage affects the retina—a thin film that lines the inner surface of the back of the eyes. It is responsible for sending light signals to the brain to be interpreted and understood. Blockage of the retinal vein leads to leakage of fluids into the retina, causing swelling and preventing oxygen circulation and your ability to see.
An obstruction in the main retinal vein is called a central retinal vein occlusion (CRVO). If it occurs in the smaller branch veins, it is called branch retinal vein occlusion (BRVO). Obstruction can also occur in the arteries supplying the eye, which include central retinal artery occlusion (CRAO) and the small branching arteries supplying the eyes, branch retinal artery occlusion (BRAO).
Types of retinal artery occlusion (eye strokes)
As discussed above, a stroke affecting the eye may result in damage to the surrounding structure that’s vital for our vision, including the retina and the optic nerve. Once an eye exam detects the signs of eye occlusion, the type is diagnosed based on its location.
Central retinal artery occlusion (CRAO): Usually occurs with sudden, profound, but painless vision loss in one eye. It is often preceded by episodes of vision loss known as amaurosis fugax, lasting seconds to a couple of minutes. It is most commonly due to a clot embolus from the carotid artery in the neck or the heart that travels to the retinal artery, causing occlusion.
Central retinal vein occlusion (CRVO): Causes sudden, painless vision loss that can be mild to severe. When this form of eye occlusion occurs, the final outcome may involve a thrombus or clot of the central retinal vein just where it enters the eye.
Branch retinal artery occlusion (BRAO): Occurs suddenly and is typically painless. Vision loss can be appreciated as a loss of the peripheral vision, with some cases also losing central vision. Vein occlusion is usually caused by a clot or plaque that breaks loose from the main artery of the neck (carotid), or from one of the valves or chambers of the heart. Loss of visual acuity with this particular form of eye occlusion will depend mostly on whether arterial blood flow has been disrupted and if swelling is present in the macula, where the focusing occurs.
Branch retinal vein occlusion (BRVO): Branch vein occlusion may result in decreased vision, peripheral vision loss, distorted vision, or blind spots. BRVO involves only one eye and is usually the result of a localized clot development in the branch retinal vein.
Eye stroke symptoms
Symptoms of eye strokes can occur suddenly or develop slowly over hours or even days. The following are symptoms of eye strokes:
Floaters – Small gray spots floating around in your field of vision. Floaters occur when blood and other fluids leak and then clump up in the fluid inside the eye.
Pain or pressure – Can signal a problem with the eye, however, true eye strokes are often painless.
Blurry vision – Steadily worsens in one section of your field of vision or all of one eye.
Complete vision loss – Can occur suddenly, or gradually over time.
Causes of eye strokes
Eye strokes are caused by obstructed blood flow damaging the retina and optic nerve, and this can occur in one of two ways: obstruction of arteries or veins preventing adequate perfusion of blood, or blockage due to a clot or thrombus preventing adequate perfusion of blood. This phenomenon typically occurs due to pre-existing conditions that create an environment that either promotes the formation of clots or very poor circulation due to hardening and narrowing of blood vessels.
Eye strokes complications and who’s at risk
While recovery from an eye stroke is possible, there can be severe lifelong complications potentially limiting vision or complete vision loss
Macular edema – Also known as inflammation of the macula, the middle part of the retina that helps with making images appear sharper. Swelling of this part of the eye can blur vision or lead to vision loss.
Neovascularization – This is a condition where abnormal vessels develop in the retina. Abnormal vessels can leak into the vitreous (fluid inside the eye) and cause floaters. In severe cases, the retina can become detached.
Neovascular glaucoma – Due to the formation of new blood vessels in the eye causing a painful increase in pressure.
Blindness – Complete loss of vision
People in their 60s with certain diseases are more likely to experience an eye stroke. These include:
- Cardiovascular disease
- High cholesterol
- High blood pressure
- Narrowing of the carotid or neck artery
Diagnosis of stroke in the eye
if you are unfortunate enough to experience sudden vision loss in one or both eyes, it is imperative to see a doctor right away, preferably an ophthalmologist. Once the doctor has completed their initial evaluation, the following are other possible tests they may consider necessary:
- Fluorescein angiography – Use of a special camera to take a series of photographs of the retina after a small amount of fluorescein (yellow dye) is injected into a vein in your arm. The fluorescein travels to the retinal vessels, exposing any abnormalities.
- Intraocular pressure
- Reflexes of the pupil
- Photos of the retina
- Slit-lamp examination
- Testing of side vision (visual fields)
- Visual acuity test (eye chart)
Eye stroke treatment tips
The treatment method chosen will often depend on the patient’s unique situation and health status. The amount of damage done generally dictates which treatment is suitable. Possible therapies include:
- Clot-busting drugs
- Ocular massage to open the retina
- Laser treatment
- Anti-vascular endothelial growth factor drugs (anti-VEGF), which are directly injected into the eye
- Pan-retinal photocoagulation therapy if you have new blood vessel formation
- High pressure, or hyperbaric oxygen
Prevention tips for stroke of the eye
If you suspect you or anyone you know is having an eye stroke, it is important to seek medical attention immediately. While it may not always be possible to prevent eye strokes from occurring, there are a few things you can do to help decrease the chances of having one.
Properly manage your diabetes – Keep glucose levels in ideal ranges as set by your doctor.
Treat your glaucoma – This condition raises intraocular pressure, increasing your risk for eye stroke. Follow the treatment plan as prescribed by your doctor to avoid any possible complication.
Control blood pressure – Poorly controlled blood pressure is a major risk factor for the contribution of eye strokes, therefore, keeping blood pressure controlled with diet and exercise, plus any prescribed medications, will help a great deal.
Manage cholesterol levels – Diet and exercise will help reduce levels in addition to any prescribed medication.
Quit smoking – Smoking can increase your risk for all types of stroke
Experiencing a sudden loss of vision can be a scary situation. If you or anyone you know happens to find themselves experiencing vision loss possibly caused by an eye stroke, seek medical attention immediately. Vigilance and the confidence that your doctor will do everything in their power to help you regain any sense of normalcy will bring you solace in this dire situation.