A retinal vein occlusion (RVO) is a temporary blockage of the blood flow in a retinal vein.   The blocked can either be of the central retinal vein or a smaller, branch retinal vein affecting just one quadrant of the retina.   Although the blockage is usually temporary, the resulting damage and complications can be ongoing. The most common complication is cystoid macular edema, or swelling in the center of the retina which directly blurs the vision. The second most common complication is retinal neovascularization, or growth of abnormal blood vessels which can lead to bleeding (vitreous hemorrhage) or detachment of the retina.

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How does retinal vein occlusion occur?
With age or other systemic risk factors such as hypertension, the small blood vessels of the eye can harden.  In the retina, the veins usually pass underneath an artery, and the resultant compression can lead to thrombosis (a blood clot)  in the vein.  Less commonly, patients have have a genetic predisposition to form blood clots that can block a vein as well.  Eventually the thrombus/clot dissolves and blood flow through the vein returns, but the blood vessels may be permanently damaged in the region affected and blood flow is still often impaired.

 

What are complications of a retinal vein occlusion?
In some cases, the damaged blood vessels leak fluid (like a hose with holes in it) and the fluid accumulates in the center of the retina, blurring the vision. This is called cystoid macular edema (CME).  In other cases, the damaged blood vessels shut down and become scarred.  If this happens in the center or the retina (macular ischemia), the vision can be permanently reduced. ​  Areas of retinal ischemia may also produce a signal for repair and new blood vessel growth.  While in theory this sounds helpful, the new blood vessels grow in a disorganized fashion and can cause large bleeds in the eye or scar tissue that leads to a retinal detachment.  I

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What is the treatment for a retinal vein occlusion?
The mainstay of treatment for CME is injections of medicine into the eye.  This procedure sounds painful, but is actually quite comfortable.  Two main classes of medications exist, anti-VEGF and steroids.  Anti-VEGF medications are non-steroid medications that suppress leakage or proliferation by damaged blood vessels.  Steroid medications help reduce many inflammatory mediators in the eye that are released after a vein occlusion and are stronger than anti-VEGF medications, but can hasten cataract progression and in some patients raise the eye pressure.   Injections are not a cure, as they usually have to be repeated regularly in order to control the edema, but most patients are able to stop injections after a year or two.  

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A retinal vein occlusion with retinal neovascularization often requires a laser treatment that ablates peripheral regions of retina that have lost their blood supply.  This procedure is performed in the office and permanently reduces the production of the signal that leads to new blood vessel growth.  Often a few Anti-VEGF injections are performed as well.