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QUESTION

WHEN DO I REFER A PATIENT WITH A BRANCH RETINAL ARTERY OCCLUSION OR CENTRAL RETINAL ARTERY OCCLUSION, WHAT IS THE WORK-UP, AND WHAT ARE THE TREATMENT OPTIONS?

Todd R. Klesert, MD, PhD

Although a thorough systemic work-up may not always yield a causative etiology, there is no such thing as an idiopathic retinal artery occlusion (RAO). RAOs are often the first manifestation of a larger, potentially serious, systemic condition that may require treatment, and therefore always warrant further evaluation. In my opinion, this is best accomplished in conjunction with the patient’s primary care physician.

The causes of RAO are many, but may be grouped into a few primary categories: embolic, coagulopathic, inflammatory/autoimmune, traumatic, infectious, and structural. Overall, embolism is the most frequent cause of arterial occlusion (Figure 8-1). For patients over the age of 40, atherosclerotic plaques in the aorta, carotid, and ophthalmic arteries are the most frequent source of emboli. In patients under 40, cardiac sources predominate: valvular disease (including septic emboli from endocarditis), arrhythmia, wall motion abnormalities, myxoma, and septal defects, such as a patent foramen ovale in the setting of deep venous thrombosis.

The suspicion for coagulopathy should increase as patient age decreases. Many of the well-established genetic risk factors for venous thrombosis (ie, Factor V Leiden mutation, prothrombin G20210A gene mutation, protein C and S deficiency, activated protein C resistance, antithrombin III deficiency) are less strongly correlated as risk factors for arterial thrombosis.¹ I therefore do not routinely order these expensive laboratory tests unless the more common causes of RAO have been excluded, or the past medical and/or family histories are suggestive of a hereditary thrombophilia. Procoagulant factors that have been associated with arterial thrombosis include antiphospholipid antibodies, anticardiolipin antibodies, elevated homocysteine levels, sickle cell disease, malignancy, blood dyscrasia, pregnancy, and oral contraceptive use (particularly in conjunction with smoking or a hereditary thrombophilia).

One inflammatory/autoimmune disease that should always be forefront in the mind of any clinician with an older patient with RAO is giant cell arteritis (GCA). Although less than 2% of RAOs are a result of GCA, the consequences of missing this diagnosis can be catastrophic. Therefore, unless an obvious embolus is visible on exam, I routinely order a stat erythrocyte sedimentation rate (ESR), C-reactive protein, and complete blood count (CBC) to assess platelets on all patients over age 55 with RAO, even if the patient does not have any other obvious signs or symptoms of GCA. Patients who do have a suspicious history for GCA should be started on high-dose corticosteroids immediately and referred urgently for a temporal artery biopsy. Some of the other inflammatory/autoimmune diseases that should be considered in the differential diagnosis of RAO, particularly in younger patients, are systemic lupus erythematosus, polyarteritis nodosa, granulomatosis with polyangiitis, Behcet disease, and Susac syndrome (Figure 8-2).

Traumatic causes of RAO are usually evident from the history. Inadvertent, prolonged pressure on the eye during surgery or during a drug- or alcohol-induced stupor is one cause. Patients undergoing prolonged spinal surgeries in a prone position are at particular risk for this complication. Occlusions can also be seen after retrobulbar anesthetic injections, periorbital steroid injections, and injections of cosmetic soft tissue fillers around the face.

Infectious causes of RAO are less common, but include Lyme, syphilis, tuberculosis, and toxoplasmosis.

Finally, structural abnormalities that can lead to RAO include carotid artery dissection, vasospasm during migraine, retinal arteriolar loops, and optic nerve head drusen.

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