Central Retinal Artery Occlusion (Eye Stroke)

What is Central Retinal Artery Occlusion (Eye Stroke)?

Central retinal artery occlusion (CRAO) is an eye condition that can cause sudden, severe vision loss. It happens when blood flow to the central retina is disrupted due to a clot or a spasm in the blood vessel, and sometimes leads to a damaged retina. This clot often originates from the carotid artery, aorta, or even the heart. While it’s not very common, an inflammation condition called giant cell arteritis can also lead to CRAO.

Considered to be like a brain stroke, CRAO increases the risk of future strokes and heart disease. Sadly, there isn’t a proven therapy to improve vision loss caused by CRAO, and patients often have a poor visual prognosis. So, the main goal of treatment is to prevent further problems like strokes and heart-related deaths. However, with early diagnosis and treatment, some patients may experience improved visuals.

What Causes Central Retinal Artery Occlusion (Eye Stroke)?

CRAO, or central retinal artery occlusion, falls into two types: nonarteritic CRAO and arteritic CRAO. The majority of cases (over 90%) are of the nonarteritic type. This usually occurs due to an embolism, which is a blockage that is carried through the bloodstream. This blockage can be a solid, liquid, or gas, and in around 70% of nonarteritic CRAO cases, there’s also a significant buildup of fatty deposits in the artery on the same side as the CRAO.

There are three main types of these blockages: cholesterol (Hollenhorst plaques), calcium, and platelet-fibrin. About half to 80% of all retinal blockages are made of cholesterol, with platelet-fibrin being the second most common at 6 – 32%. Calcium blockages are less everyday, accounting for 6 – 16% of cases.

Cholesterol and platelet-fibrin blockages often come from fatty deposits in the carotid arteries, while calcium blockages typically come from the heart valves. Under examination, these blockages can look different. Cholesterol blockages are often orange; calcium blockages are white, and platelet-fibrin blockages appear dull white.

Sometimes other materials like talc, fat from long bone fractures, and infectious material can also block the central retinal artery, especially in patients with bloodstream infections.

Another condition that leads to CRAO is in-situ thrombosis, which is a blood clot formed in the area. Various factors like certain diseases (e.g., autoimmune diseases, inflammatory states, and conditions affecting blood clotting) and cosmetic facial injections or fillers can also cause CRAO.

Arteritic CRAO usually stems from diseases causing inflammation of the blood vessels like giant cell arteritis, lupus, and Takayasu arteritis, among others. To differentiate the two types of CRAO, medical professionals often check for inflammatory markers such as erythrocyte sedimentation rate and C-reactive protein.

Central retinal artery occlusion can be further categorized into: nonarteritic CRAO, caused by a permanent blockage in the central retinal artery; nonarteritic CRAO with cilioretinal artery sparing; transient nonarteritic CRAO, which involves a temporary blockage lasting a few minutes to hours; and arteritic CRAO, often caused by diseases affecting the blood vessels.

Risk Factors and Frequency for Central Retinal Artery Occlusion (Eye Stroke)

The condition known as CRAO affects about 1 to 1.9 for every 100,000 people in the United States and less than 2% of these cases involve both eyes. In different regions such as Japan, Germany, and Korea, the rate ranges from 1.8 to 2.7 per 100,000 people each year. This rate goes up with age, being approximately 10 per 100,000 people per year in adults 80 years or older.

Although the average age of people affected by CRAO and the rate of incidence may vary depending on the location, it usually happens among those aged 60 to 70. Yet, it can also occur in children due to reasons that are not related to blocked arteries such as trauma, heart valve diseases, and infections.

Men are slightly more likely to have CRAO than women. People diagnosed with CRAO tend to have a lower life expectancy of 5.5 years compared to their counterparts who do not have CRAO but are of the same age, they tend to live up to 15.4 years.

Some of the risk factors for developing CRAO are similar to those for other disorders caused by blood clots. These include:

• High blood pressure
• Smoking
• Hyperlipidemia (high levels of fat in the blood)
• Diabetes
• A higher-than-healthy body mass index (BMI)
• Dyslipidemia (abnormal amount of lipids in the blood)
• Irregular heart rhythms (such as atrial fibrillation)
• Conditions that make your blood more likely to clot
• Heart disease, including rheumatic heart disease and other heart valve diseases
• Male gender

Up to 40% of people with CRAO are found to have significant narrowing of the carotid artery on the same side.

Signs and Symptoms of Central Retinal Artery Occlusion (Eye Stroke)

Central Retinal Artery Occlusion (CRAO) typically shows up as sudden, painless loss of vision in one eye, a process that happens within seconds. Some people might experience brief periods of visual loss before the full onset of the condition and may also have a history of diseases linked to arteriosclerosis, which is the hardening of the arteries. You can rule out ophthalmic artery occlusion, optic nerve abnormalities, and clogged short posterior ciliary arteries if the patient cannot perceive light at all.

People with CRAO often have severe vision loss in one eye and a Marcus Gunn pupil, a condition where one pupil reacts less to light than the other. This might not be detectable if the other eye is already damaged because of diseases like glaucoma. Vision can range from complete loss of light perception to being able to count fingers. About 75% of CRAO patients have quite poor vision. Some cases might have better than 20/40 vision due to various factors like good blood circulation, certain points in the eye being spared from blockage, or partial CRAO.

An eye exam can show mild whitening in the retina, which can only be seen through a technique called optical coherence tomography (OCT), before the full symptoms appear. All other eye exams will appear normal.

A thorough eye exam is crucial to diagnose CRAO. The interior of the eye can appear normal initially. However, over time, the retina can become white, and a red spot might appear. This red spot is due to the thin layer at the center of the retina allowing the red of the choroid (part of the eye filled with blood vessels) to show through while the white retina blocks the rest of it. You can appreciate this change more if you compare it with the healthy eye. Some cases of CRAO might not show a red spot.

Abnormalities in the small arteries or veins in the eye or slowing of blood flow can also be noticed. Blood flow can be slow through the retinal artery and can be seen during an eye exam using a 90D lens or by a test using a colored dye. The irregular narrowing of the retinal arteries can also be noticed. About 15% to 25% of people have cilioretinal arteries which, if not blocked, can maintain central vision despite CRAO. However, the visual field or range of vision can be severely restricted in these cases.

Arterial blockages can be seen in up to 40% of cases. Other diseases like commotio retinae, Tay-Sachs disease, and Niemann-Pick disease can also present with a red spot but can be distinguished based on the way they present clinically. Arteritic CRAO, which involves inflammation of the arteries, typically has a pale, swollen disc suggestive of arteritic anterior ischemic optic neuropathy (damage to the optic nerve due to blocked blood flow) along with the characteristics of CRAO. It should be suspected in older patients with a history of jaw pain during meals, muscle pain, and scalp tenderness. A pulse check on the same side should also occur.

Testing for Central Retinal Artery Occlusion (Eye Stroke)

Central Retinal Artery Occlusion (CRAO) is similar to having a stroke, but in the eye’s retina. Therefore, the checks done for CRAO closely mirror those conducted when a person had a stroke or a mini-stroke.

In CRAO checks, the eye doctor would take a picture of the back of the eye and run a test called an Optical Coherence Tomography (OCT) of the macula, the central part of the retina. A typical sign of CRAO is a whitish look in the affected eye compared to the other. There may also be bright spots at the macula. The OCT test reveals increased reflective properties in the retina’s inner layer while some CRAO cases may show extreme reflection of the middle layer of the macula. Over time, the inner layer of the retina starts to thin.

A dye test, known as fundus fluorescein angiogram (FFA), is not necessarily needed for the CRAO diagnosis. However, if carried out, it tends to show a slow movement of the dye in the tiny blood vessels in the eye. In cases where CRAO doesn’t involve arteries, the eye parts that need blood fill up normally. If CRAO involves arteries or blocks the eye’s main artery, the test may show less blood reaching these areas. However, sometimes, the FFA test may appear normal in CRAO cases.

For people showing up with CRAO symptoms, immediate tests would be blood sugar check, blood count, clotting state, including prothrombin time (PT), international normalized ratio (INR), and activated partial thromboplastin time (PTT). Tests for inflammation such as ESR and CRP should be conducted to rule out giant cell arteritis, a condition in which blood vessels in your body, including those in your eyes, become swollen. If these inflammation markers come out high and symptoms of giant cell arteritis align, strong medications should be started immediately, and a biopsy of the temporal artery should be planned within two weeks.

If CRAO symptoms have been present for less than four and a half hours, a head CT scan should be done without contrast dye to check for bleeding in the brain and decide if clot-dissolving therapy is needed. Other tests may be considered according to each patient’s risk factors and medical history. These tests may include hemoglobin A1c, lipid profile, Rh factor, antinuclear antibody, fluorescent treponemal antibody absorption test, checks for clotting status, imaging of the carotid artery, and heart tests.

Since the most common cause of CRAO is the carotid artery’s blockage, imaging tests– which can include carotid duplex ultrasound, CT, magnetic resonance, and digital subtraction angiography–are vital. If the carotid artery appears normal, heart imaging tests should follow. Doctors from various fields, including eye specialists, heart doctors, family doctors, internists, and neurologists, need to work together when treating patients with CRAO.

Treatment Options for Central Retinal Artery Occlusion (Eye Stroke)

The outlook for central retinal artery occlusion (CRAO) remains poor even with treatment, and current research is looking for more effective and safer therapies. Currently, there’s no agreed-upon best treatment for CRAO, but early administration of intravenous (IV) clot-dissolving drugs shows promise. Treatments are aimed at improving blood flow or oxygen levels in the retina, and may involve widening blood vessels, lowering eye pressure to dislodge a clot, increasing oxygen levels, surgically removing the clot, or breaking up the clot with drugs. Healthy lifestyle changes and controlling overall health can help prevent a recurrence.

Different treatments have been tried with mixed success, including:

* Immediate eye massage: By rapidly increasing and decreasing eye pressure with a 3-mirror Goldmann lens or fingers, an obstructing clot may be dislodged. However, this method is not standard for CRAO and its effectiveness has not been definitively proven.

* Drugs to reduce eye pressure: A combination of IV acetazolamide, mannitol, and timolol eye drops may lower eye pressure, potentially improving blood flow.

* Draining a small amount of fluid from the eye: This method, known as anterior chamber paracentesis, might dilate retinal arteries, but it can also pose risks including internal eye bleeding and infections. Its benefits in treating CRAO are uncertain.

* Carbogen: This mix of 95% oxygen and 5% carbon dioxide can help the retina get more blood, but it may not improve outcomes in acute CRAO.

* Hyperventilation into a paper bag and inhaling 10% carbon dioxide: By inducing a state of acidic blood and widening blood vessels, this method could potentially improve retinal blood flow.

* Pentoxifylline: This medication, used to improve blood flow by increasing red blood cell flexibility and lowering blood thickness, has shown some limited success in improving retinal blood flow in CRAO.

* Isosorbide dinitrate: The drug can cause blood vessels to widen, although comprehensive studies on its effectiveness are currently lacking.

* Supplemental oxygen

* IV methylprednisolone: Used for CRAO caused by giant cell arteritis, this drug reduces inflammation and retinal swelling.

* IV clot-dissolving therapy: An IV infusion of tissue plasminogen activator, a medication that dissolves clots, is the most commonly used treatment for CRAO in the U.S., although its effectiveness is still being researched.

* Intra-arterial clot dissolving therapy: A catheter is placed into the eye artery and clot-dissolving medication is administered. However, this treatment carries safety concerns and is recommended only for patients who cannot receive IV clot dissolving therapy and who have come for treatment within 6 hours of onset.

* Hyperbaric oxygen therapy: By increasing the amount of oxygen in the blood, this therapy can potentially improve retinal function.

* Laser embolectomy: Using a specific type of laser, the procedure dissolves an obstructing clot.

* Surgery to remove the thrombus: Although it has been performed in a few cases, this procedure is not a standard treatment for CRAO.

What else can Central Retinal Artery Occlusion (Eye Stroke) be?

When trying to diagnose a condition called Central Retinal Artery Occlusion (or CRAO), doctors also need to consider several other health conditions that could cause similar eye issues.

• The blockage of the ophthalmic artery: This artery supplies the blood and oxygen to the eye. If this artery gets blocked, it could cause serious damage to the eye and the area around it. A complete blockage may result in total blindness, and some typical signs in the eye, like a “cherry red spot”, might not be seen due to the damage.
• Paracentral Acute Middle Maculopathy: This condition shows up as increased brightness of a layer of the eye when seen on an OCT (eye-imaging test). This can sometimes progress to CRAO. It’s part of a group of conditions caused by insufficient blood flow to the eye.
• Purtscher Retinopathy: This condition can look like a temporary case of CRAO. It shows up as small, white patches on the retina (often called “cotton wool spots”).
• Hypertensive Retinopathy: This condition results from very high blood pressure and affects both eyes. It can cause changes in blood vessels, swelling, and the appearance of “cotton wool spots” around the optic disc.

Doctors also need to be aware that a “cherry red spot” in the eye could indicate other possible issues, such as an injury to the eye, inflammation around the optic disc, certain genetic disorders, or negative reactions to some drugs. Deciding on the right diagnosis always requires careful consideration of all these possibilities.

What to expect with Central Retinal Artery Occlusion (Eye Stroke)

Despite recent improvements in medicine, the outlook for vision recovery after Central Retinal Artery Occlusion (CRAO) remains quite poor. Studies have found that only 10% to 20% of patients with CRAO regain functional vision. One significant study involving 130 patients noted that if the CRAO was temporary and nonarteritic, about 82% of those affected showed sight improvement from a baseline of only being able to see fingers or worse. Furthermore, about 67% of eyes with nonarteritic CRAO and a clear cilioretinal artery experienced vision improvement. This compared to just 22% with nonarteritic CRAO without a clear cilioretinal artery. Most improvements in vision happened within the first 7 days.

The American Heart Association includes CRAO in its definition of an acute ischemic stroke, a sudden episode of neurological dysfunction caused by a lack of blood flow to the brain, spinal cord, or retina. Similar to other kinds of ischemic strokes, CRAO carries an increased risk of future blood flow problems. Also, patients with retinal artery blockages may experience higher death rates compared to the general population.

Possible Complications When Diagnosed with Central Retinal Artery Occlusion (Eye Stroke)

Patients with Central Retinal Artery Occlusion (CRAO) often experience thinning in the inner layer of the retina and damage to the optic nerve over time. Approximately 20% of such patients develop abnormal blood vessels in the iris, which is usually observed around 1 to 2 months after the initial disease onset. However, this can sometimes occur within a week. Treatment for this usually involves burning the abnormal blood vessels with laser therapy (panretinal photocoagulation) and sometimes they may require an injection that inhibits blood vessel growth (anti-vascular endothelial growth factor agents).

In cases of arteritic CRAO, where it’s associated with inflammation of blood vessels (arteritis) in giant cells, the other eye also has a high chance of being affected. In such situations, high-dose steroids can be used to prevent the disease from spreading to the other eye. It’s important to note that there could be a significant risk of blood clots in the arteries (arterial thromboembolic events) and potentially life-threatening situations after the occurrence of CRAO. Therefore, patients should be made aware of these risks.

These complications can include:

• Thinning in the inner layer of the retina
• Damage to the optic nerve
• Abnormal blood vessels in the iris
• Potential risk of disease affecting the other eye
• Significant risk of blood clots in the arteries
• Potentially life-threatening situations

Preventing Central Retinal Artery Occlusion (Eye Stroke)

If someone experiences sudden and painless loss of vision, it may be due to a condition known as CRAO. It’s vital to seek immediate medical help if this happens, as waiting too long could cause permanent damage to the eyes. To test their vision regularly, people should try closing one eye at a time to see if they notice any sudden changes. Even though there’s currently no guaranteed treatment for CRAO, getting diagnosed quickly and starting any available treatment as soon as possible could potentially improve the visual results.

Things like high blood pressure, diabetes, heart disease, or high cholesterol can increase the risk of developing CRAO. Living a healthier lifestyle (including not smoking) and taking medications can help manage these risk factors. Additionally, it’s important to see a healthcare provider for a comprehensive exam. This might include seeing an eye and/or vascular specialist to figure out what’s causing the CRAO and to discuss how to best treat it.

The outlook for people with CRAO can vary. Some may regain partial or even full sight, but it’s important to know that around 80% of patients may permanently lose their vision. This could depend on factors like how much of the eye’s blood supply was cut off and how effective any treatments were.

Following up with eye care professionals and other pertinent specialists regularly is key in monitoring the patient’s eyesight, managing risk factors and taking care of any complications that may arise. It’s vital to acknowledge the emotional toll that sudden vision loss can take. Providing information about resources like mental health counseling or support groups can be a great help in navigating the psychological challenges of living with CRAO.

Eating a balanced diet, exercising regularly, keeping blood pressure and cholesterol levels in check, and not smoking can all help in reducing the risk of further vascular events. This is an essential part of managing the condition and preventing future complications.