Retinal Vein Occlusion (blocked vein)

Branch Retinal Vein Occlusion

Retina is a light-sensitive tissue that lines the inside of the eyeball and transmits the visual information to the brain. Each eye’s retina has one main central vein which branches into numerous smaller retinal vein branches.

Retinal vein occlusion can affect the main vein (central retinal vein occlusion) or any of the branches. 


If the occlusion affects the central vein, or one of the branches that supply the most important part of the retina, called the macula, the vision will be reduced.  The location and severity of occlusion, as well as the health of the remaining blood vessels, determine the extent and duration of vision loss. 

If the occlusion affects one of the smaller, peripheral branches, the person is usually not aware of any symptoms.


Conditions that affect blood vessels, such as high blood pressure, diabetes, blood clotting disorders and smoking are risk factors for a vein occlusion.

Why is my vision reduced?

There are several effects of a blocked vein

  • Numerous haemorrhages occur in the affected part of the retina. These can be seen as dark blotches in the vision
  • The retina swells because the vein which drains the blood is not working
  • If the blockage is severe, the blood supply is too poor for that part of the retina to continue to function.
  • If there is no blood supply, the eye can grow new blood vessels which rather than helping the circulation, can cause severe complications such  as bleeding in the eye or glaucoma.


A blocked vein can not be unblocked. It is up to your remaining circulation to support the recovery of the eye. The treatment is aimed at helping this process and preventing/ treating complications of the vein occlusion, such as growth of new abnormal blood vessels. Treatment will be individually tailored to you and may involve:

  • Observation only if the vein occlusion is an incidental finding picked up during routine eye examination and the vision is not affected
  • Injections if the retinal swelling is affecting the vision or causing structural damage. Injections are given every month initially, then depending on the swelling. Most patients who do develop recurrent retinal swelling will require on average 7-8 injections in the first year of treatment, 4-5 injections in the second year and fewer still later on. Some patients may only need a few injections. The amount of swelling and therefore the treatment duration will depend on how well the remaining circulation kicks in.
  • Laser is sometimes used to improve the swelling, but more often it is used to prevent or treat the growth of abnormal blood vessels

What to expect if you have been diagnosed

At your initial visit, we will test your vision and thoroughly examine your eye. This is include a high-definition OCT scan which examines your retina in microscopic detail to detect any swelling or structural change. Your circulation will be assessed in fine detail using the latest technology OCT Angiography (OCTA). If required, a further test called a Fluoroscein Angiogram may be performed.

Your ophthalmologist will then go over the test results with you, explaining what they mean and treatment plan will be put into place.

To find out more about retinal vein occlusion treatment, visit our Macula Clinic website.