Retinal Vein Occlusion: Causes and Management

What Is Retinal Vein Occlusion?

Blood vascular system if important for every organ of the human body. Arteries carry oxygen and nutrients to the organs while veins carry waste metabolites and carbon dioxide from the organ. The retina is a thin layer of cells that helps in vision. Any problem in the retina may lead to blurred vision or blindness.

The retina is also supplied with veins and arteries. When the vein of retina gets blocked, the condition is termed as retinal vein occlusion. Retinal vein occlusion is a common cause of blindness. Due to retinal vein occlusion, there may be irreversible damage to the eyes. There is increased pressure inside the eyes that may result in swelling, leakage, and bleeding.

How The Vision Is Affected By Retinal Vein Occlusion?

Retinal vein occlusion causes vision loss through the following mechanisms:

Macular edema: Macular edema in retinal vein occlusion is a common cause for vision loss. The macula is the central part of the eye that provides visual acuity. Because of retinal vein occlusion, there is a leakage of fluid, bleeding or swelling in the macula leading to vision loss. 

Neovascular glaucoma: Because of retinal vein occlusion, there is an increased production of Vascular Endothelial Growth Factor. There is an increased formation of new blood cells. This results in increased pain and pressure. It may lead to glaucoma.

Blindness: Retinal vein occlusion is an emergency condition requiring immediate medical intervention. The untreated condition may lead to permanent vision loss.

Neovascularization: There is an increased production of VEGF after retinal vein occlusion. VEGF is produced by various ocular cells. VEGF promotes neovascularization. Neovascularization may result in the development of floaters. In severe cases, there is an increased risk of retinal detachment.

What Are The Causes Of Retinal Vein Occlusion?

The exact cause of retinal vein occlusion is unknown. However, certain factors increase the risk of developing this condition. Following factors may increase the risk of retinal vein occlusion:

High Blood Pressure: High blood pressure may increase the risk of retinal vein occlusion. Almost 73% of patients above 50 years of age with Central retinal vein occlusion has hypertension.

High Cholesterol: Hyperlipidaemia increases the risk of retinal vein occlusion.

Diabetes: Due to the presence of comorbid hypertension in diabetic patients, people with diabetes are also at risk for developing retinal vein occlusion.

Glaucoma: As the intraocular pressure increased, there is an increased risk of retinal vein occlusion.

Smoking: People who smoke are at increased risk of retinal vein occlusion.

Age: Retinal vein occlusion commonly occurs in children above the age of 55 years.

What Are The Symptoms Of Retinal Vein Occlusion?

Following are the symptoms of retinal vein occlusion:

• Blurred vision
• Progressive or dramatic vision loss
• Painless reduction in monocular vision
• Distorted vision
• Pain and ocular pressure
• Sudden occurrence of floaters

What Are The Types Of Retinal Vein Occlusion?

There are following types of Retinal Vein Occlusion:

Branched Retinal Vein Occlusion: Four retinal veins drain blood from the retina. Each vein drains almost one-fourth of the blood from the retina. The blockage of any of these branched veins is known as Branched Retinal Vein Occlusion.

Hemiretinal Retinal Vein Occlusion: When either the primary superior branch or primary inferior branches of retina gets blocked, the condition is termed as Hemiretinal Central Retinal Vein Occlusion.

Central Retinal Vein Occlusion: Occlusion of the Central vein situated at the level of the optic nerve is termed as Central Retinal Vein Occlusion. Patients suffering from Central Retinal Vein Occlusion have more severe symptoms as compared to branched Retinal Vein Occlusion.

Retinal Vein Occlusion is also divided based on the presence or absence of ischemia. In cases involving ischemia, there is an increased risk of macular edema, neovascularization, and neovascular glaucoma. 

How To Diagnose Retinal Vein Occlusion?

The Retinal Vein Occlusion should be differentially diagnosed with several other ocular conditions such as Retinal detachment, Retinal Artery Occlusion, Temporal Arteritis, Hypertensive Retinopathy, Ocular ischemic Syndrome, and Radiation Retinopathy. Following are the diagnostic methods for Retinal Vein Occlusion:

Fluorescein angiography: In this diagnostic test, fluoresce in dye is injected in the blood. Photographs of the retina are then taken to evaluate the presence and extent of Retinal Vein Occlusion. Based on angiography, a proper treatment regimen is decided.

Optical coherence tomography: This diagnostic method is performed to evaluate the level of swelling in the macular region. It helps in monitoring the health of the eye. It also helps to analyze whether a particular treatment is effective.

What Are The Treatment Options For Retinal Vein Occlusion?

Retinal damage cannot be reversed and thus the treatment is aimed to prevent further vision loss. Macular swelling is a common cause of vision loss in Retinal Vein Occlusion. Following drugs are used to reduce and prevent further swelling:

Steroids: Steroids are used for reducing the inflammation and prevent the production of inflammatory mediators. Triamcinolone is used for reducing the symptoms and complications of Retinal Vein Occlusion. By reversing the capillary permeability, triamcinolone reduces swelling. Dexamethasone intravitreal implant is also used to reduce inflammation.

Anti VEGF Medications: Anti-VEGF is injectable medication required to be given every month. These drugs reduce the growth of new blood vessels and prevent further vision loss. Ranibizumab is an Anti-0VEGF drug used for Retinal Vein Occlusion.