What is Retinal Vein Occlusion?
A retinal vein occlusion is a blockage of tiny blood vessels that run through the retina. These blood vessels normally carry blood away from the retina, and when they are blocked, swelling and bleeding can occur within retina. If this swelling and bleeding occurs in the macula, the central part of the retina, then it can cause a decrease in vision or distorted vision. The blockage can involve the main retinal vein (Central Retinal Vein Occlusion), or it can affect a smaller tributary vein (Branch Retinal Vein Occlusion). Retinal vein occlusions most commonly occur in individuals over the age of 50 years, but younger patients can also experience this disease. It is second only to diabetic retinopathy as the most common vascular disease of the eye.
Causes of Retinal Vein Occlusion
Retinal vein occlusions most commonly occur due to hardening of arteries and formation of a clot within the vein, causing a blockage. The most common risk factors for developing a retinal vein occlusion include:
- High Blood Pressure
- High Cholesterol
- Heart Disease
- Blood clotting disorders
- Inflammatory and Infectious diseases (Sarcoid, vasculitis, TB)
Vein occlusions generally happen without a reason, but they are sometimes associated with high blood pressure, clotting problems, or glaucoma. In the early stages of damage, some of the small blood vessels become twisted and small spots of blood appear in the retina. It is important to monitor this stage as it can progress to a more severe form that can cause blindness. After a vein occlusion, these small retinal blood vessels that are normally water-tight start to leak. If the leakage becomes substantial, your vision may become worse. We call this macular edema. To stop the leakage, gentle laser treatment might be done to cauterize the leaky vessels. Sometimes a steroid or other medication injection is used as well or instead. In many cases these treatments may be combined over time.
Treatment can usually help to prevent the vision from worsening and occasionally can make it better. However, not all vein occlusions respond to treatment and in some cases your vision may be permanently damaged. You may require a fluorescein angiogram to assess the blood flow in your eye, which helps us to decide on the appropriate treatment. In the more advanced stages of damage, abnormal blood vessels start to grow on the retina’s surface. These vessels can break and bleed, causing a vitreous hemorrhage. Even worse, these abnormal blood vessels can cause the retina to detach, a potentially blinding problem. In these cases, more aggressive laser treatment is applied to the retina to stop the vessel growth. Laser can prevent blindness. In some cases, the normal retinal blood vessels die off from the vein occlusion (called ischemia) and the vision is permanently damaged. In very advanced stages of damage, an operation may be needed to clear out the blood in the eye or repair a retinal detachment. This operation, called vitrectomy, involves making three small incisions and using miniature forceps, scissors and other instruments to restore a more normal retinal anatomy. Sometimes, however, the vision cannot be improved despite any efforts.
What is Branch Retinal Vein Occlusion?
Branch retinal vein occlusion (BRVO) is a common retinal vascular disease, which occurs in the elderly. When blood flow in a vein is inhibited or blocked, blood and fluid begin to pool causing swelling of the macula. This is known as macular edema and is the cause for blurry and decreased vision.
Branch retinal vein occlusions can be diagnosed by a photographic test called fluorescein angiogram as well as an optical coherence tomography scan.
Causes, Symptoms & Treatment
Those with hypertension, diabetes, glaucoma, ocular inflammation or carotid artery disease are at a higher risk for BRVO. Compromised blood flow and blood content can lead to blockages and reduction in blood flow.
Sudden blurred vision and blind spots in the center of the visual field are symptoms of a branch retinal vein occlusion.
While spontaneous vision improvement does occur, continual macular edema causes most vision loss. Laser treatment is recommended in these instances. When too much blood obscures the laser treatment, a drug can be injected into the eye to reduce macular edema and improve vision.
What is Central Retinal Vein Occlusion?
Central retinal vein occlusion (CRVO) occurs when the central retinal artery becomes blocked. As the sole source of blood supply and drainage for the retina, a blockage of this vein causes a back up of blood and fluid leading to retinal damage and vision loss. As the retina becomes deprived of oxygen, the eye produces new blood vessels, which can lead to hemorrhaging and neovascular glaucoma, which can lead to total blindness and loss of the eye.
Causes of Central Retina Vein Occlusion
Those with hypertension, diabetes, glaucoma, diabetes and atherosclerosis, or hardening of the arteries, are all factors in the development of CRVO. Compromised blood flow and blood content can lead to blockages and reduction in blood flow.