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The retina is the nerve tissue in the back of the eye that requires healthy blood circulation for visual function. Blood enters the retina through the central retinal artery and drains out of the retina through the central retinal vein. When the central retinal vein becomes blocked, this is called a central retinal vein occlusion or CRVO. The severity of the blockage correlates with the severity of the vision loss. There are partial and complete central retinal vein occlusions.
When the vein becomes blocked, blood cannot exit, so this results in blood and swelling building up in the retina. If there is a complete blockage, the eye also becomes starved for oxygen and nutrients that come from healthy blood flow.
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CRVO |
The prognosis for central retinal vein occlusions is, unfortunately, generally poor. The outlook is best predicted by the initial vision. Most patients who present with central retinal vein occlusions either stay the same or worsen over time. If the vision is only mildly affected due to limited partial blockage, it sometimes can improve without treatment. In the multi-center Central Retinal Vein Occlusion Study (CVOS), in patients with partial or nonischemic CRVO, only 10% improved, while 50% stayed the same, and 1/3 worsened. In more severe cases of complete or ischemic CRVO, usually the vision loss is permanent, and it is rare to get spontaneous improvement.
Treatment options for central retinal vein occlusion, unfortunately, have been limited. No large scale treatment trial thus far has proven any beneficial treatment. It is important to try to identify untreated risk factors and manage those to try to prevent progression or recurrence. Risk factors for central vein
occlusion include a history of glaucoma, a history of systemic hypertension, smoking, hyperlipidemia (high cholesterol and triglycerides), history of diabetes, history of atherosclerosis (often characterized by prior coronary artery disease or stroke), or problems with blood clotting, blood vessel inflammation (vasculitis), or increased blood viscosity. Oral contraceptive use has been associated with this condition as well. It is important that these are addressed and controlled as well as possible. Aspirin therapy is generally recommended to try and prevent further occlusion.
Because of the grim visual prognosis in central retinal vein occlusions, some treatments are being tried. The current leading therapy is to use injections in the eye of a class of medications called VEGF inhibitors. It has been shown that when the circulation is decreased, VEGF molecules are released in the retina and are an important mechanism by which the retina gets damaged. Studies thus far show that blocking VEGF in some patients can help minimize the damage from this. Anti-VEGF drugs have become the main treatment for another blood vessel disorder called exudative macular degeneration, and their benefit has been proven for that condition. Studies are ongoing for central retinal vein occlusions, but so far the results do show that a significant number of patients do benefit, at least in the short term. Long-term, carefully controlled clinical trials are ongoing and still are necessary. The most common anti-VEGF drug is Avastin (bevacizumab). This anti-VEGF drug is approved for systemic use in cancer patients and is used in a very small quantity (0.05 cc) in the eye. We have been using this in the eye since 2005. Most patients who show improvement from this often require some degree of continued treatment long term, but the need and frequency of injections is very individual to each patient and will be determined by testing and monitoring by your physician. Another anti-VEGF agent available is Lucentis (ranibizumab), which is made by the same pharmaceutical company. It has been approved for the eye only for macular degeneration at this point and is significantly more expensive. Clinical trials for both anti-VEGF drugs are ongoing. A recent retrospective study of our patients revealed that more than 50% of patients did achieve significant benefit from Avastin therapy for central retinal vein occlusion. Again, further studies are ongoing. Another form of treatment that is being investigated is the injection of anti-inflammatory steroid medication inside the eye. A large clinical trial is studying this potential treatment.
In cases of very severe central retinal vein occlusion, abnormal blood vessels can develop in the eye. These blood vessels can cause hemorrhaging but also can grow into the drainage system of the eye causing a severe form of glaucoma that can cause pain and loss of all visual function. If your central retinal vein occlusion is in the more severe category, your
eye will need to be monitored more closely and frequently for this, especially in the first 6 months after development. If abnormal blood vessels are detected, laser treatment sometimes combined with anti-VEGF therapy is used to control this. It is done to prevent the painful severe form of glaucoma but does not improve the vision. If there is significant hemorrhaging, vitrectomy surgery in combination with laser is sometimes necessary. Glaucoma surgery is sometimes needed as well if the problem becomes more advanced.
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