What Is Retinal Vein Occlusion?

​

Retinal vein occlusions occur when there is a blockage of veins carrying  blood with needed oxygen and nutrients to the nerve cells in the retina. A blockage in the retina’s main vein is referred to as a central retinal vein occlusion (CRVO), while a blockage in a smaller vein is called a branch retinal vein occlusion (BRVO).

​

What are the symptoms of Retinal Vein Occlusion?

​

Many patients are completely asymptomatic and are diagnosed incidentally on a routine checkup by their doctor or optometrist. 

Blurred vision or  floaters due to vitreous haemmorhage are other potential symptoms and should always be investigated by a healthcare professional. 

​

What are the causes of Retinal Vein Occlusion?

​

Most BRVOs occur at an arteriovenous crossing—an intersection between a retinal artery and vein. These vessels share a common sheath (connective tissue), so when the artery loses flexibility, as with atherosclerosis (hardening of the arteries), the vein is compressed.  

The narrowed vein experiences turbulent blood flow that promotes clotting,  leading to a blockage or occlusion. This obstruction blocks blood drainage and may lead to fluid leakage in the center of vision (macular edema) and ischemia—poor perfusion (flow) in the blood vessels supplying the macula. 

​

The common risk factors for BRVO are:

• Uncontrolled high blood pressure

• Being overweight or obese 

• Cardiovascular (heart) disease

• Glaucoma

• In younger patients who suffer BRVO, an abnormal tendency to develop blood clotting is also possible

​

What are the treatments for Retinal Vein Occlusion?

​

Treatment begins with identifying underlying risk factors and treating them. Risk factors are assessed using several methods:

• Blood pressure monitoring

• Determining if blood cholesterol or lipid levels are elevated

• Blood tests, if appropriate, to determine if there is an abnormal tendency  to form blood clots 

 

Eye treatment is aimed at treating retinal complications rather than at  trying to relieve the blockage itself. Macular oedema, the main reason for visual loss from BRVO, is often treated with intraocular (in-the-eye) injections of anti-VEGF drugs designed to stop the growth of abnormal new blood vessels in the eye and decrease leakage. Local anaesthetic eye drops are given before the injections to numb the eye and minimize discomfort. 

There are currently 3 anti-VEGF drugs:

• Avastin® (bevacizumab®)

• Lucentis® (ranibizumab®)

• Eylea® (aflibercept®)

In several large clinical studies, all 3 of these anti-VEGF drugs have demonstrated good results, with over 50% of patients enjoying significant visual improvement. The use of these drugs may require frequent retreatment, but injection schedules are determined on a case-by-case basis.

Injections of steroids including a steroid implant (Ozurdex) may also be used treat macular oedema.

Laser photocoagulation also has a role in reducing vision threatening complications of retinal vein occlusion.