What is Central Retinal Vein Occlusion?
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.
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 a partial blockage, it sometimes can improve without treatment. A multi-center clinical trial called the Central Retinal Vein Occlusion Study showed that 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, vision loss is often permanent and it is rare to get spontaneous improvement.
What is the treatment for Central Retinal Vein Occlusion?
Although the visual prognosis is often poor for CRVO, several treatment options are available. First, it is important to identify untreated risk factors and manage those in order to decrease the risk of progression or recurrence. Risk factors for central vein occlusion include a history of glaucoma, systemic hypertension, smoking, hyperlipidemia (high cholesterol and triglycerides), diabetes mellitus, 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. Aspirin therapy is often recommended to try and prevent further vascular compromise. Most patients with retinal vein occlusion are asked to see their internist for a thorough medical evaluation.
One of the main complications of CRVO is macular edema, which is swelling in the central part of the retina. Several therapies have shown promise in managing this condition. Intravitreal administration of medications like bevacizumab (Avastin) that block Vascular Endothelial Growth Factor (VEGF) may have a role. Other treatments for macular edema from CRVO include intravitreal steroid administration. A sustained-release steroid implant is available as well.
In cases of severe CRVO, abnormal blood vessels can develop in the eye. These blood vessels can grow into the drainage system of the eye, causing a severe form of glaucoma that can lead to 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 is sometimes combined with anti-VEGF therapy. Vitrectomy surgery is sometimes necessary. Glaucoma surgery may be needed as well if the problem becomes more advanced.