CENTRAL AND BRANCH RETINAL ARTERY OCCLUSION

By 

Sonia Mehta 

, MD, Vitreoretinal Diseases and Surgery Service, Wills Eye Hospital, Sidney Kimmel Medical College at Thomas Jefferson University

Central retinal artery occlusion occurs when the central retinal artery becomes blocked, usually due to an embolus. It causes sudden, painless, unilateral, and usually severe vision loss. Diagnosis is by history and characteristic retinal findings on funduscopy. Decreasing intraocular pressure can be done within the first 24 h of occlusion to attempt to dislodge the embolus. If patients present within the first few hours of occlusion, some centers catheterize the carotid/ophthalmic artery and selectively inject thrombolytic drugs.

Retinal artery occlusion may be due to embolism or thrombosis.

Emboli may come from any of the following:

• Atherosclerotic plaques
• Endocarditis
• Fat
• Atrial myxoma

Thrombosis is a less common cause of retinal artery occlusion but can be seen with systemic vasculitis such as SLE and giant cell arteritis, which is an important cause of arterial occlusion that requires prompt diagnosis and treatment.

Occlusion can affect a branch of the retinal artery as well as the central retinal artery.

Neovascularization (abnormal new vessel formation) of the retina or iris (rubeosis iridis) with secondary (neovascular) glaucoma occurs in about 20% of patients within weeks to months after occlusion. Vitreous hemorrhage may result from retinal neovascularization.

Retinal artery occlusion causes sudden, painless, severe vision loss or visual field defect, usually unilaterally.

The pupil may respond poorly to direct light but constricts briskly when the other eye is illuminated (relative afferent pupillary defect). In acute cases, funduscopy shows a pale, opaque fundus with a red fovea (cherry-red spot). Typically, the arteries are attenuated and may even appear bloodless. An embolus (eg, a cholesterol embolus, called a Hollenhorst plaque) is sometimes visible. If a major branch is occluded rather than the entire artery, fundus abnormalities and vision loss are limited to that sector of the retina.

Patients who have giant cell arteritis are 55 or older and may have a headache, a tender and palpable temporal artery, jaw claudication, fatigue, or a combination.

• Clinical evaluation
• Color fundus photography and fluorescein angiography

Central Retinal Artery Occlusion

The diagnosis is suspected when a patient has acute, painless, severe vision loss. Funduscopy is usually confirmatory. Fluorescein angiography is often done and shows absence of perfusion in the affected artery.

Once the diagnosis is made, carotid Doppler ultrasonography and echocardiography should be done to identify an embolic source so that further embolization can be prevented.

If giant cell arteritis is suspected, ESR, C-reactive protein, and platelet count should be done immediately. These tests may not be necessary if an embolic plaque is visible in the central retinal artery.

Patients with a branch artery occlusion may maintain good to fair vision, but with central artery occlusion, vision loss is often profound, even with treatment. Once retinal infarction occurs (as quickly as 90 min after the occlusion), vision loss is permanent.

If underlying giant cell arteritis is diagnosed and treated promptly, the vision in the uninvolved eye can often be protected and some vision may be recovered in the affected eye.

• Sometimes reduction of intraocular pressure
• Immediate treatment is indicated if occlusion occurred within 24 h of presentation. Reduction of intraocular pressure with ocular hypotensive drugs (eg, topical timolol 0.5%, acetazolamide 500 mg IV or po), intermittent digital massage over the closed eyelid, or anterior chamber paracentesis may dislodge an embolus and allow it to enter a smaller branch of the artery, thus reducing the area of retinal ischemia. Some centers have tried infusing thrombolytics into the carotid artery to dissolve the obstructing clot. Nonetheless, treatments for retinal artery occlusions rarely improve visual acuity. Surgical or laser-mediated embolectomy is available but not commonly done. These treatments are sometimes shown to be effective in small case series, but none have strong evidence to support efficacy.

• Consider immediate measures to reduce intraocular pressure in patients who have sudden, painless, severe loss of vision.
• Patients with occlusion secondary to giant cell arteritis should receive high-dose systemic corticosteroids.

• Central or branch retinal artery occlusion can be caused by an embolus (eg, due to atherosclerosis or endocarditis), thrombosis, or giant cell arteritis.
• Painless, severe loss of vision affects part or all of the visual field.
• Confirm the diagnosis by doing funduscopy (typically showing a pale, opaque fundus with a red fovea and arterial attenuation).
• Do color fundus photography and fluorescein angiography and search for an embolic source by doing Doppler ultrasonography and echocardiography.
• Treat immediately if possible with ocular hypotensive drugs (eg, topical timolol or IV or oral acetazolamide), intermittent digital massage over the closed eyelid, or anterior chamber paracentesis.

Caroline R. Baumal, in Atlas of Retinal OCT: Optical Coherence Tomography, 2018

Branch retinal artery occlusion (BRAO) results from obstruction of one of the branches of the central retinal artery. The most common cause is emboli secondary to either carotid plaques or cardiac. Less common, nonembolic causes include vasospasm and inflammatory and hypercoagulable disorders. Medical evaluation for cardiovascular and carotid disease is indicated because of the association with increased morbidity and mortality. Patients are typically 70 years or older and present with painless, unilateral, partial visual loss.

Amaurosis fugax preceding persistent loss of vision may represent emboli causing temporary occlusion of the retinal artery with subsequent release into the distal circulation. Location of the BRAO is often at the retinal artery bifurcation, where the artery lumen is narrower. Ischemic retinal whitening and inner retinal edema develop along the path of the occluded branch artery. Other features include visible emboli in 60% of eyes, narrowing and boxcarring of the affected vessel, segmentation of blood flow, and cotton wool spots. Clinical features are usually diagnostic in acute BRAO, but fluorescein angiography and OCT are useful to demonstrate BRAO features (see Fig. 1). OCT can be a great aid in diagnosing inner retinal atrophy and loss of the inner retinal layer architecture after acute BRAO findings have resolved.