Retinal artery occlusion is the cessation of blood flow from the arterial vessels in the retina. 90% of patients are over 40 years old and it is more common in men. Especially in the case of central retinal artery occlusion, complete vision loss may occur. In this article, we will discuss the symptoms of retinal artery occlusion, the causes of eye vessel occlusion, diagnostic methods, and treatment options for retinal artery occlusion in detail.
What is Retinal Artery Occlusion?
Retinal artery occlusion is defined as the blockage of the arterial vessels that carry oxygen to the nerve cells in your retina. Due to this blockage, oxygen cannot reach the retina, and serious vision loss may develop. There are three different types depending on the artery that is blocked.
Central Retinal Artery Occlusion (CRAO)
The main artery supplying blood to the eye is the ophthalmic artery, and blockage in the main artery of the retina is called central retinal artery occlusion. This condition usually leads to severe vision loss. The incidence ranges from 0.87 to 1.7 per 100,000 people.
In CRAO, vision loss is usually severe. In 90% of cases, vision loss is at the level of light perception and hand movement. In 75% of cases, the outcomes are poor. The American Heart Association considers this condition an acute ischemic stroke.
However, approximately 25% of individuals who develop CRAO have an additional artery called a cilioretinal artery in their eyes. The presence of this artery significantly reduces the likelihood of damaging central vision. With the presence of a cilioretinal artery, 80% of eyes achieve 20/50 vision or better.
Branch Retinal Artery Occlusion (BRAO)
A blockage occurring in a smaller artery is referred to as branch retinal artery occlusion. Branch retinal artery occlusion is a rare condition where any of the branches of the central retinal artery is blocked. It accounts for 38% of retinal artery occlusions.
The blockage is seen in 90% of cases in the temporal branches, and there is sudden vision loss in the area corresponding to the blocked artery. It can cause loss of a portion of your visual field. If the affected area is not in the center of the eye or is relatively small, it may go unnoticed without any symptoms.
In BRAO, vision field loss is usually permanent. However, central visual acuity is 20/40 or better in 80% of eyes. The visual prognosis is generally better compared to CRAO.
Cilioretinal Artery Occlusion
The presence of a cilioretinal artery is approximately 30% in the population. Cilioretinal artery occlusion is a rare condition reported in conjunction with various systemic diseases. The incidence of symptomatic cilioretinal artery occlusion is even lower and accounts for about 5.3 to 7.1% of retinal artery occlusions.
In this type of occlusion, vision loss may vary depending on damage to the optic nerve. It may be associated with emboli, systemic lupus erythematosus, antiphospholipid syndrome, migraine, pregnancy, and systemic hypertension.
What are the Symptoms of Retinal Artery Occlusion?
Symptoms of retinal artery occlusion appear suddenly, and patients often experience vision problems without any warning signs. The severity of the symptoms varies depending on the location of the blockage.
Sudden and Painless Vision Loss
The most prominent feature of retinal artery occlusion is sudden and painless vision loss. This usually occurs in one eye. The absence of pain is an important characteristic that distinguishes it from painful eye conditions like glaucoma.
Vision loss can develop within seconds or minutes. You may notice that you cannot see with one eye upon waking up in the morning or suddenly experience changes in your vision during daily activities. Therefore, individuals experiencing sudden vision loss should seek an eye specialist immediately.
In some cases, temporary vision loss may occur before permanent vision loss. This condition is called amaurosis fugax and lasts from a few seconds to a few minutes. Vision returns to normal afterward, but this is a serious warning sign. Individuals experiencing temporary vision loss should urgently consult an eye doctor as it may indicate impending permanent retinal artery occlusion.
Degree of Vision Loss
The area of the retina affected by the blocked vessels determines the severity of vision loss. In central retinal artery occlusion, more severe findings are observed compared to branch occlusion.
In central retinal artery occlusion, 74-90% of patients have light perception or finger-counting level of vision. This often leads to severe vision loss. The degree of vision loss is related to the location of the blockage.
A blockage in a smaller artery may cause loss of a portion of your visual field. If the affected area is not in the center of the eye or is relatively small, it may go unnoticed without any symptoms. Therefore, some branch occlusions are incidentally detected during routine eye examinations.
Other Visual Symptoms
Vision loss may not only manifest as general blurriness. There may be narrowing of the visual field, blurriness, and loss of visual field. Depending on the affected retinal area, loss may occur in a specific part of the visual field.
Visual field defects may present as loss of part of an object, dimming in peripheral vision, or a curtain falling sensation. In central retinal artery occlusion, loss in the center of vision is more pronounced, while in branch occlusion, a more localized blind spot may be noticeable.
There may be a sudden decrease in visual acuity. A sensitivity to light may develop. In some cases, you may start seeing colors as more faded or dull. This is related to the oxygen deficiency affecting the cells responsible for color perception in the retina, but it is not as common as sudden vision loss.
Causes and Risk Factors of Retinal Artery Occlusion
The causes of eye vessel occlusion are generally related to clots coming from another part of your body or structural problems in the vessels. There are multiple mechanisms that trigger the formation of occlusions.
Embolic Occlusion
Emboli are the most common cause of retinal artery occlusion. A small embolus in your bloodstream can block the retinal artery. Emboli account for two-thirds of branch occlusions and one-third of central artery occlusions.
There are three main types of emboli: cholesterol, calcium, and platelet-fibrin. Cholesterol and platelet-fibrin emboli usually originate from plaque deposits in your carotid arteries. Calcium emboli, on the other hand, break off from your heart valves and reach the eye.
Individuals with carotid artery disease have a significantly increased risk. One-third of patients over 50 have carotid artery occlusion. Among patients with embolic occlusion, 10% develop cerebral ischemia.
Thrombus Formation
A thrombus, known as a blood clot, can form directly in the retinal artery. Two-thirds of central retinal artery occlusions develop due to thrombus. Atherosclerotic disease, arteriosclerosis, and inflammatory conditions predispose to thrombus formation.
Plaques that accumulate in the vessel over the years can also cause occlusion. Individuals with clotting disorders have an increased risk of thrombus. Conditions such as sickle cell disease, polycythemia vera, and multiple myeloma facilitate clot formation.
Arteritic Causes
It is seen in approximately 4.5% of cases of giant cell arteritis. This vascular inflammation condition can lead to retinal artery occlusion. The incidence of temporal arteritis in patients over 50 is below 5%.
Autoimmune conditions such as systemic lupus erythematosus, polyarteritis nodosa, and Behçet’s disease can also cause vascular inflammation. Occlusions caused by these reasons generally occur in younger patients.
Risk Factors
The incidence of retinal artery occlusion significantly increases with age. Most patients are in their 60s, and it is more common in men than women. The average age is around 65.
Hypertension is present in 60% of patients. Diabetes is detected in 25% of patients. High cholesterol, heart disease, and atherosclerosis are significant risk factors.
Heart valve disease, arrhythmias such as atrial fibrillation increase the risk of clot formation. The use of oral contraceptives, pregnancy, and intravenous substance abuse also pose risks. Smoking accelerates arteriosclerosis and increases the risk of clotting.
Increased intraocular pressure due to glaucoma may increase the risk of retinal artery occlusion. Conditions affecting both eyes are quite rare and occur in only 1-2% of cases.
How is Retinal Artery Occlusion Diagnosed?
Early and accurate diagnosis is critical for treatment success. If you notice sudden vision loss, you should come for an eye examination as soon as possible. Your doctor will diagnose by taking your history and performing an ophthalmological examination. Various imaging methods support the diagnosis.
Fundus Examination
The eye doctor will first listen to your medical history and symptoms. Then, they will thoroughly examine the front and back parts of the eye. Your pupil will be dilated with drops, and a dilated eye examination will be performed.
Fundus examination is one of the most important steps in diagnosis. The doctor examines the condition of your retina and optic nerve using an ophthalmoscope. Direct and indirect ophthalmoscopy can reveal retinal nerve fiber edema or loss.
In central retinal artery occlusion, a cherry-red spot is seen. The retina around the macula becomes pale, but the fovea retains its color. This contrast appears as a bright red spot during the fundus examination. The retina in the area of occlusion appears whitish or pale.
It is appropriate to perform fundus photography for documentation. In the early stage, the fundus may appear normal, but the typical appearance is a pale white color of ischemic edema in the retina and preservation of red color in the fovea.
Fluorescein Angiography
Fluorescein angiography is an important diagnostic method. A dye is injected from your arm, and this dye enters the bloodstream. Sodium fluorescein binds to plasma proteins at about 80%. The unbound portion is stimulated by blue light to emit green light.
The doctor takes pictures of your retina with a special camera. Normally, intravenously administered sodium fluorescein appears in the central retinal artery after 10-12 seconds. Arteries fill within 1-3 seconds, and then veins fill completely within 10 seconds.
Fluorescein angiography clearly shows where blood flow has stopped. It can be seen that the dye does not reach the affected arterial branches. In retinal artery occlusion, filling delay is observed. The test is used to evaluate perfusion or slow perfusion in ischemic fundus diseases.
Optical Coherence Tomography (OCT)
OCT creates cross-sectional images of the retina. It shows the structure of the retinal layers in detail. Retinal edema and structural changes are observed.
In the inner retinal layers, thickening and increased reflectivity are observed. Reflectivity decreases in the photoreceptor and retinal pigment epithelium layers. Detailed images of the central retina are provided, and swelling in the inner layers of the affected area is shown.
Loss is detected in superficial and deep vascular networks in areas consistent with the occlusion. OCT images can be taken in widths of 3×3, 6×6, or 8×8 mm. In the acute phase, an increase in reflectivity of the inner retinal layer and thickening of the retina are observed.
Blood Tests and Cardiovascular Assessment
Blood tests should be requested to investigate the cause of the occlusion. Complete blood count, blood sugar, cholesterol levels, and coagulation tests are performed. Inflammatory markers such as sedimentation rate and CRP are measured.
A cardiology assessment is performed. Tests such as EKG, echocardiography, or Holter monitor may be requested to detect heart rhythm disorders. Carotid color Doppler ultrasound evaluates your carotid artery. Atherosclerotic narrowing and calcified plaques may be seen in Doppler ultrasound during etiological investigation.
How is Retinal Artery Occlusion Treated?
Unfortunately, there is no clinically proven treatment for central retinal artery occlusion. Treatments are generally applied within the first 24 hours. Irreversible damage to the retina occurs within 90-100 minutes. However, early intervention is critical for preserving visual function.
Emergency Treatment Approaches
Timing is extremely important for the success of treatment. For any treatment to potentially be effective, it must be applied within 4 to 6 hours after the onset of symptoms. In the first few hours, there is a possibility of recanalization in the patient who presents.
Ocular massage is the first and most practical treatment method. Pressure is applied to the eyeball for 10-15 seconds and then suddenly released. This procedure increases vasodilation, enhances blood flow, and helps to displace the embolus peripherally. This massage can be applied with repeated interruptions.
Carbon dioxide inhalation may help in the dilation of retinal arteries. Inhaling a mixture of 95% oxygen and 5% carbon dioxide has the potential to increase blood flow. Additionally, the application of vasodilator agents such as nitroglycerin and isosorbide dinitrate increases retinal oxygenation.
Thrombolytic therapy may be attempted in the early hours. Intravenous tissue plasminogen activator is effective within the first 4.5 hours. However, clinical studies have not demonstrated the effectiveness of this treatment.
Reducing Intraocular Pressure
Reducing intraocular pressure may increase perfusion pressure. A small amount of fluid is drawn from the anterior chamber, which is applied to displace the embolus. Medications such as acetazolamide and mannitol can be used to lower intraocular pressure.
Hyperbaric Oxygen Therapy
There is information suggesting that hyperbaric oxygen therapy is beneficial. Increasing arterial oxygen pressure stimulates nitric oxide synthesis, promoting vasodilation. It aims to maintain high retinal oxygen levels until recanalization occurs. It is particularly beneficial when performed in the first 6-8 hours.
It is recommended to apply this treatment to patients who present in the first hours. Early hyperbaric oxygen therapy has resulted in an increase in visual acuity in 82.9% of the group. If started within the first 24 hours, the effectiveness of the treatment is more successful.
Corticosteroid Treatment
In cases of arteritic occlusion caused by giant cell arteritis, high-dose corticosteroid treatment should be initiated. Methylprednisolone is administered intravenously at a dose of 1 g/day for 3 days. After the initial high-dose treatment, the dose is gradually reduced based on the patient’s condition for maintenance therapy.
Treatment of Complications
Retinal ischemia can trigger iris neovascularization. In this case, panretinal photocoagulation is required. Intravitreal anti-VEGF injections may also be used. The development of neovascular glaucoma is observed in a small portion of cases.
Post-Treatment Follow-Up
Problems that allow clot formation in the body should be investigated. A cardiology examination, echocardiogram, and carotid Doppler ultrasound are appropriate. Patients are evaluated for neovascularization development after a period of 4-6 weeks. Managing risk factors is crucial to reduce the risk of occlusion in the other eye or cerebral vessels.
Frequently Asked Questions
Is retinal artery occlusion dangerous?
Yes, retinal artery occlusion is a serious condition. It leads to sudden vision loss similar to a stroke in the eye. It may also indicate clot formation in your body. Therefore, your risk of stroke or heart attack increases.
Retinal tissue is extremely sensitive to oxygen. Damage can develop within minutes when blood flow is interrupted. For this reason, it is considered one of the eye emergencies, and early intervention plays a critical role.
Can retinal artery occlusion be treated?
Unfortunately, there is no clinically proven treatment for central retinal artery occlusion. Early initiation of treatment may preserve some vision, but in most cases, vision loss may be permanent.
For any treatment to be effective, it must be applied within 4 to 6 hours after the onset of symptoms. Unfortunately, none of these treatments have been shown to change the natural course of the disease as predicted.
Less than 10 to 20% of patients regain functional vision. Visual gain is possible with early diagnosis and treatment. Especially if intervention is made within the first few hours, the chance of vision recovery increases.
Does vision loss return?
Your level of vision depends on the type of occlusion, its location, and how early the intervention was made. In central retinal artery occlusion, vision loss is usually severe.
However, the presence of a cilioretinal artery leads to better visual outcomes. In 80% of eyes, 20/50 vision or better is achieved. In branch retinal artery occlusion, vision field loss is usually permanent, but central visual acuity is 20/40 or better in 80% of eyes.
Especially if the macula is not affected and treatment is started early, vision can significantly return. However, permanent losses are more common in arterial occlusions.
Does the other eye get affected?
Only 1-2% of cases involve both eyes. It usually occurs in one eye. However, among patients with retinal artery occlusion due to giant cell arteritis in one eye, approximately 25-50% may develop a similar condition in the other eye if left untreated.
In patients treated quickly with high-dose corticosteroid therapy, the risk of involvement in the other eye is significantly reduced.
In Summary, Retinal Artery Occlusion
Retinal artery occlusion is a serious condition that leads to sudden vision loss in the eye. Essentially developing within minutes, this condition is an eye emergency that requires immediate intervention. Unfortunately, there is no proven definitive treatment, but interventions performed in the first few hours can reduce vision loss. Therefore, it is vital to consult an eye doctor immediately if you experience sudden and painless vision loss. You can protect yourself from this condition by keeping risk factors such as hypertension, diabetes, and cholesterol under control. Regular eye examinations and healthy lifestyle habits are the most effective ways to protect your eyes.
Retinal artery occlusion is a serious condition that leads to sudden and painless vision loss in the eye. Learn detailed information about its symptoms, causes, and treatment methods.
