Retinal vein occlusion is an eye condition caused by a blockage in one of the blood vessels at the back of the eye. There are two types of retinal vein occlusion, branch retinal vein occlusion (BRVO) and central vein occlusion (CRVO), which can affect the eye in different ways. This guide explains the differences between them, and how they can be detected during an eye test.

What is central retinal vein occlusion?

Central retinal vein occlusion refers to the blockage of the main retinal vein, which drains blood from the retina (the layer at the back of eye). Blockage of this vein can cause blood and excess fluid to build-up and leak into the retina, collecting in the area responsible for central vision, called the macula. This fluid build-up can lead to a condition called macula oedema, where the macula swells and thickens, leading to distorted vision.

Over time, this fluid build-up can damage the light receptors in the retina and smaller capillaries in the eye, which can lead to reduced and blurry vision.

What is branch retinal vein occlusion?

Branch retinal vein occlusion tends to be more common, and it affects one of the smaller branch veins that each carry blood away from one quarter of the retina and feed into the central retinal vein. 

It has similar features to CRVO, except they are confined to the portion of the eye drained by the affected vein, so reduced vision may only be experienced in a specific section. 

What causes a retinal vein occlusion?

The most common cause of retinal vein occlusion is thought to be atherosclerosis, a condition that causes plaque (a mixture of fat, calcium and other things found in blood) to build up inside the arteries, restricting blood flow.

There are also several factors that could potentially put people at a higher risk of developing a retinal vein occlusion. These include:

  • High blood pressure (hypertension) – it’s estimated that around 65% of the UK population aged 65 and over experience this 1
  • Diabetes
  • High cholesterol
  • Glaucoma
  • Certain blood disorders
  • Smoking

How is retinal vein occlusion detected?

OCT scans can be particularly useful in detecting retinal vein occlusion, as they provide a very detailed 3D image of the back of the eye and all the layers that make up the retina. They take just a few seconds to complete, and can be easily added to your normal eye test.

With a baseline image on file, your optometrist will be able to check your results against national averages to spot anything that might indicate the presence of an occlusion. One of the main things they’ll be looking at is the thickness of the retinal layers to check for any swelling or fluid build-up. OCT scans can also be used to examine the macula (the centre of the retina that is responsible for the detail in the images we see) to check for signs of macular oedema which can develop as a result of an occlusion.

Why regular OCT scans are important for managing RVO

If you have been diagnosed with a retinal vein occlusion, you will be referred on to an eye specialist (ophthalmologist) who will decide the best treatment type for you. Most treatment types are focused on preventing further occlusions developing and preserving your vision. Whichever treatment type you have, you will need to see your ophthalmologist regularly in order to assess whether your treatment is working, and to make sure you aren’t developing any complications.

Regular OCT scans can be used to keep an eye on retinal layer thickness, to ensure that your treatment plan is effective. OCT is particularly useful for this because it can detect it when other testing, such as fluorescein angiography (a special dye that makes the eye’s blood vessels easy to see for imaging), can sometimes miss.2 It’s likely that you’ll need to be monitored for a couple of years.


1. CG127 Hypertension: Clinical management of primary hypertension in adults. (August 2011). Accessed 10 March 2020.

2. Accessed 10 March 2020.