Central Retinal Artery Occlusion - Causes, Symptoms, Diagnosis, and Management

Introduction

Central retinal artery occlusion (CRAO) is an obstruction of the central retinal artery and is characterized by vision loss. It is more frequent in males in comparison to females. Patients in the above fifty age bracket are most commonly affected. However, younger patients may also suffer from CRAO if an inappropriate systemic condition is present.

What Is the Vascular Supply of the Retina?

The retina is a multilayered bundle of tissue present in the posterior-most region of the eye. It primarily helps in sending the visual senses to the brain. Arteries and veins richly supply the retina of the eye. It is supplied by the ophthalmic artery that is subdivided into central retinal and cilioretinal arteries.

What Is the Main Causative Factor Behind Central Retinal Artery Occlusion?

The central retinal artery blockage is mainly caused by the formation of a blood clot (thrombi) or emboli (moving blood clot) inside the blood vessels. The factors responsible for the construction of thrombi in the blood vessels are:

• Giant cell arteritis or temporal arteritis. Giant cell arteritis is the inflammation of the lining of the arteries, especially in the temporal region.

• Inflammatory diseases.

• Atherosclerotic plaques.

• Collagen-vascular diseases.

• Cholesterol disorders.

What Is the Mechanism Involved Behind the Development of Central Retinal Artery Occlusion?

Partial or complete blockage of the lumen of the central retinal veins by thrombi results in inadequate oxygen in the blood (ischemia). The ischemic retina is then damaged, resulting in edema of the retina. When the edema resolves, the retina gets wasted, or its size reduced (atrophied).

What Are the Risk Factors Linked to Central Retinal Artery Occlusion?

Several risk factors contribute to the development of central retinal artery occlusion. These factors include:

• Smoking.

• Hypertension.

• Obesity.

• Diabetes.

• Cardiovascular diseases.

• Coagulation disorders.

What Are the Clinical Presentations of Central Retinal Artery Occlusion?

Patients suffering from central retinal artery occlusion often report sudden vision loss. The vision loss is either partial or involves the entire field of vision.

• In the early lesions, the back portion of the eye consisting of retina, macula, and blood vessels appears normal.

• In case of partial obstruction of the artery, the vision loss is transient, with the vision recovery occurring within eight to twenty-four hours.

What Are the Different Techniques Used to Diagnose Central Retinal Artery Occlusion?

Central retinal artery occlusion diagnosis encompasses the patient's complete history followed by clinical examination, imaging, and lab tests.

• History - Patients are asked about any episodes of transient vision loss. Also, detailed medical history, particularly a history of cardiovascular disease, diabetes, and atherosclerosis, is requested.

• Clinical Examination - Detailed evaluation of the fundus (part of the eyeball) region without dilating the eyes with medication. In earlier stages, the fundus appears normal.

  • On fundoscopic examination, a pale retina with a cherry-red spot is the classic clinical sign observed in patients suffering from central retinal artery occlusion.

  • Box Scarring and emboli are also visualized sometimes through the slit-lamp technique. Boxscarring manifests the sluggish blood flow.

    • Chronic clinical signs of CRAO includes:

    • Pale optic disc.

    • Thin retina.

    • Decrease in vision.

• Imaging - Imaging techniques are used to assess the blood flow. The imaging techniques used include:

  • Optical coherence tomography (OCT) assesses the edema of the retina in the acute stages.

  • Fluorescein angiography (FA) determines the sluggish blood flow and filling up of the arteries.

  • Computed tomography (CT) head is taken in case of intracranial hemorrhage suspicion.

  • Electroretinography is either normal or gets reduced owing to retinal ischemia.

  • In elderly patients, monitoring the heart and blood flow in the arteries is investigated. It is done with the help of electrocardiography and ultrasonography.

• Lab Tests - Lab tests are conducted to rule out any other systemic condition. Patients above fifty years get tested for erythrocyte sedimentation rate (ESR), C-reactive protein, and complete blood count (CBC). However, patients below fifty undergo tests to rule out other hidden cardiovascular diseases, coagulation disorders, autoimmune diseases, and inflammatory conditions.

What Are the Conditions That Share Similarities With Central Retinal Artery Occlusion?

Occlusion of the retinal artery shares similarities with other similar conditions. It is imperative to rule out the following conditions before coming to a definitive diagnosis.

• Branch retinal vein occlusion.

• Ophthalmic artery occlusion.

• Carbon monoxide poisoning.

• Ocular ischemic syndromes.

• Globe rupture.

• Retinal detachment.

How Is Central Retinal Artery Occlusion Managed?

There is no consensus regarding the specific therapy for central retinal artery occlusion. Acute cases are emergency cases requiring immediate admission to the stroke center.

Management of CRAO is primarily aimed at improving the oxygen supply to all the regions. It comprises both general management strategy and medical management with follow-up.

General Management of CRAO:

Massage around the region helps improve the blood supply in that region and helps in dislocating the thrombi from its place.

Medical Management of CARO Includes:

• Administration of eye drops reduces the pressure inside the eye with drugs like Timolol and Acetazolamide.

• Oxygen supplementation.

• Inhaling carbon dioxide inside a bag helps in causing dilation of the retinal arteries.

Is It Possible to Prevent CARO?

People with underlying systemic diseases are regularly monitored for any adverse changes in the eye. In addition, patients are educated about the importance of immediate ophthalmologist referral in case of sudden vision loss.

• Patients of central retinal artery occlusion associated with giant cell arteritis are immediately treated with the administration of steroids. It will continue for twelve months.

• In patients with chronic renal disease, increased ESR, and age below fifty, steroids are avoided and replaced with Tocilizumab.

What Are the Complications Associated With Central Retinal Artery Occlusion?

The ultimate complication of central retinal artery occlusion is complete vision loss. Other complications include:

• There is the formation of blood vessels in different parts of the eye. For example, blood vessels are formed in the pigmented part of the eye (iris) and retina.

• Due to invasive surgical interventions, there is bleeding or hemorrhage inside the brain or the eye's middle layer (choroid region).

What Is the Prognosis of Central Retinal Artery Occlusion?

Central retinal artery occlusion has an abysmal future outlook. The prognosis of the condition depends on the amount of retinal edema. The loss of vision associated with it is usually permanent. Although, visual acuity improves after some time.

Conclusion

Central retinal artery occlusion is a vascular disorder of the retinal blood vessel. It is characterized by sudden vision loss due to the central artery's narrowing and obstruction. It lacks specific treatment. Early diagnosis with palliative care helps in preventing blindness.