Background
Central retinal vein occlusion (CRVO) and branch retinal vein occlusion (BRVO) are retinal vascular disorders which occur when a vein in the retina becomes blocked. The occluded vein becomes swollen and leaks serum into the retina. This fluid collects in the center of the retina causing macular edema. If the macula becomes swollen, central vision declines.
If macular edema can be reduced, vision often improves. Laser treatment for BRVO was the first treatment shown to decrease macular edema, and cause improvement in vision. More recently, medications such as Avastin which make blood vessels less leaky have been used to decrease macular edema.
Evidence
Avastin has been studied extensively, and has been shown to reduce macular edema in patients with macular degeneration and diabetic retinopathy. In a recent study of patients with BRVO, Avastin decreased retinal edema in 92% of patients, and vision improved in over 70% (1). A similar study of seven patients with CRVO showed some improvement in vision in all patients (2). These studies are recent, and long term results are not yet known. In a significant number of cases, there is a tendency for edema to return as the medication wears off. Many patients require more than one injection.
Procedure
The treatment is a brief and typically painless office procedure. Topical anesthesia is applied, and then the medicine is injected into the central cavity of the eye using a fine needle. The injection may cause mild temporary discomfort.
Risks
Injections to the eye are relatively safe. Hemorrhage, infection, cataract, and retinal detachment may occur, but are uncommon. Systemic risks of Avastin are rare due to the very small dose and placement of the drug directly into the eye. Systemic risks include elevated blood pressure, stroke, and heart attack.
Alternatives
Laser treatment for macular edema from BRVO has been shown to decrease edema and improve vision in some patients. There is no proven treatment for macular edema due to CRVO. Steroid injections are currently being studied in patients with macular edema due to retinal vein occlusions.
Comment
Most patients with retinal vein occlusions have already lost some vision, and even with treatment may lose more. While Avastin was not initially developed to treat retinal vein occlusions, it shows great promise in providing stability and improvement in vision. Avastin, while usually safe, has some risks for systemic and ocular complications. These risks should be weighed against the potential benefit of preservation and improvement of vision.
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