Retinal Vein Occlusions by: Adam AufderHeide, MD, PhD
Retinal vein occlusions are defined as a blockage in one of the veins that transports blood from the retina back to the heart. They are one of the most common causes of vision loss due to vascular disorders in the eye.
If one thinks of the eye as a camera, the retina is the film in the camera. Like all major organs, the retina has an arterial system, which feeds blood from the heart to the retina, and a veinous system, which takes blood from the retina back to the heart. The venous system is organized like the branches and trunk of a tree. Smaller veins start collecting arterial blood, feeding it into progressively larger branch veins and finally into the central retinal vein.
There are two types of retinal vein occlusions. A branch retinal vein occlusion is defined as blockage of one of the veins before it reaches the central retinal vein. A central retinal vein occlusion is defined as blockage of the large vein that collects all of the blood from the branch veins.
When a vein in the retina is blocked, it causes damage to the retina by creating ischemia (lack of adequate blood flow to retina) swelling and bleeding.
Patients with a retinal vein occlusion may be asymptomatic with normal vision or experience painless loss of vision. The visual prognosis associated with a vein occlusion is variable, with the final vision a function of multiple factors, including the location and severity of the occlusion, the amount of retinal ischemia, the amount of swelling within the macula, and the time between onset of the occlusion and the initiation of treatment. Complications of an untreated retinal vein occlusion include permanent vision loss, neovascular glaucoma, pain and even loss of the eye.
The risk factors for a retinal vein occlusion are high blood pressure, increasing age, high cholesterol, diabetes, and glaucoma.
Retinal vein occlusions are treated by a retina specialist. Retina specialists are physicians (M.D.) and ophthalmologists who have completed additional fellowship training to manage diseases of the retina such as macular degeneration, retinal vein occlusions, macular degeneration and diabetic retinopathy. They are also surgeons, trained to treat other retinal problems such as retinal detachment, macular pucker and macular hole.
The most common treatable cause of vision loss in retinal vein occlusions is swelling of the retina in the area of best vision, the macula. This is called macular edema. Vascular Endothelial Growth Factor (VEGF), a factor released from the retinal tissue damaged by the vein occlusion, makes the retinal blood vessels leaky and like a soaker hose dripping water onto a sponge, the macula swells and the vision declines.
VEGF can also lead to growth of abnormal new blood vessels from the retina which can lead to loss of vision by bleeding into the vitreous gel that fills the back cavity of the eye.
A retina specialist can treat both of these problems with anti-VEGF medications, steroids, lasers and intraocular surgery. Our goal is to maximize vision, reduce the chance of vision threatening complications, and help patients continue to enjoy their vision and lifestyle.
Ultimately, the best way to avoid a retinal vein occlusion is minimizing one’s risk factors. Keeping your blood sugar, blood pressure, cholesterol, and weight under control is a great first step. Regular visits to your primary care doctor are important.