Central Retinal Vein Occlusion
A retinal vein occlusion occurs when a vein in the retina becomes blocked, leading to a backflow and stagnation of blood in the retina. This backflow causes hemorrhages and leakage of fluid into the retinal nerve tissue. With incomplete circulation, the eye becomes deprived of oxygen and nutrients and can be permanently damaged. Depending on the location of the blockage, two different types of retinal vein occlusions are possible. A central occlusion involves the main vein in the eye and a branch occlusion affects a smaller branch of a vein.
Vision loss and pain are characteristic symptoms of a retinal vein occlusion. Retinal swelling (edema), loss of blood supply (ischemia), and abnormal blood vessel growth (neovascularization) are all associated with the condition.
Certain diseases can increase the risk of developing a retinal vein occlusion. These include diabetes, high blood pressure, certain blood disorders, atherosclerosis and glaucoma. There is a ten percent risk that a vein occlusion will occur in the second eye of a previously affected individual.
Treatment options for retinal vein occlusions include laser surgery and intraocular injections of medications that prohibit abnormal blood vessel growth (anti-VEGF drugs) and anti-inflammatory agents (corticosteroids). In some cases, surgery may be recommended to control complications. Managing any contributing health issues is very important.
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People with diabetes mellitus can develop damage to retinal blood vessels due to high blood sugar levels. This is referred to as diabetic retinopathy. The damage can be categorized into two types: the early stage known as nonproliferative diabetic retinopathy and the more advanced stage known as proliferative diabetic retinopathy.
In the earlier stages, damaged blood vessels within the retina leak blood and fluid causing areas of swelling and deposition of exudates. When the central retina is affected it is called macular edema and can cause visual symptoms. As the disease progresses, instead of leaking, the blood vessels close which deprive the eye of oxygen and nutrients. This condition is called ischemia. In response to the ischemia, abnormal blood vessels grow on the surface of the retina and cause scarring and bleeding into the cavity of the eye. The growth of the abnormal vessels is called neovascularization and the bleeding is known as a vitreous hemorrhage. The scarring can lead to shrinking and subsequent pulling of the retina causing it to detach itself from the back of the eye. This is called a traction retinal detachment. If the abnormal blood vessels grow on the front of the eye, drainage channels may be blocked causing increased pressure within the eye. This is a painful condition known as neovascular glaucoma.
In its early stages, diabetic retinopathy has no visual symptoms. Vision is compromised when edema and/or ischemia occurs in the macula. With the development of scarring and neovascularization, more severe vision loss can occur due to a vitreous hemorrhage or a traction retinal detachment.
Diabetes mellitus is the underlying cause of this condition. Blood sugar and blood pressure control are essential in reducing the risk of developing diabetic retinopathy and subsequent loss of vision.
The best treatment for diabetic retinopathy is strict control of blood sugar levels. Diagnosis is based on findings of a dilated eye exam and retinal imaging studies using fluorescein angiography and optical coherence tomography. Once the disease is present and symptoms appear, multiple treatment modalities may be used depending on clinical findings and the severity of the condition. Therapies include laser surgery, intravitreal injections and vitrectomy surgery.
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