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Retinal Vein Occlusion

Arteries carry blood from the heart to other parts of the body, and veins carry the blood back to the heart. A blockage in an artery or vein is called an occlusion or stroke.

When the flow of blood to the retina is blocked, it is called an artery occlusion. This could occur because of a blot clot, fat (lipid) or calcium. This usually has a poor prognosis.

When the flow away from the retina is blocked, it is a retinal vein occlusion (Retinal Vein Occlusion). This could occur often from a block within the vein or from external compression from a hardened artery crossing over the retinal vein.

When a retinal vein is blocked, it cannot drain blood from the retina. This leads to haemorrhages (bleeding) and leakage of fluid from the blocked blood vessels into the surrounding retinal tissue.

There are three types of RVO:

Central retinal vein occlusion (CRVO) is the blockage of the main retinal vein.
Branch retinal vein occlusion (BRVO) is the blockage of one of the smaller branch veins.
Hemi retinal vein occlusion (HRVO) is the blockage of 2 branches of the retinal vein, usually the upper two or the lower two branches of the retinal vein

How does retinal vein occlusion (RVO) cause vision loss?
  • Macular oedema: The macula is the small, central area of the retina that allows sharp, detailed vision, such as that necessary for reading. Blood and fluid leaking into the macula cause swelling, a condition called macular edema, which causes blurring and/or loss of vision.
  • Neovascularization: RVO can cause the retina to develop new, abnormal blood vessels, a condition called neovascularisation. These new vessels may leak blood or fluid into the vitreous, the jelly-like substance that fills the inside of the eye. Small spots or clouds, called floaters, may appear in the field of vision. With severe neovascularisation, the retina may detach from the back of the eye.
  • Neovascular glaucoma: New blood vessels in certain parts of the eye can cause pain and a dangerous increase in pressure inside the eye.

Blindness: The complications of RVO, especially if they are not treated, can lead to irreversible loss of vision

Who is at risk of developing RVO?

It is more likely to occur in people with diabetes, and possibly high blood pressure, high cholesterol other health problems that affect blood flow.

How do you diagnose Retinal Vein Occlusions?
  • By your symptoms
  • Clinical examination of the eye. The changes caused by RVO may be seen by examination of the retina with an instrument called a slit lamp.
  • Optical coherence tomography (OCT): A machine scans the retina and provides very detailed images of the retina and macula. The light beam is painless. The doctor will use OCT images to objectively monitor the status of the disease throughout the course of your treatment.
  • Fluorescein angiography: This is a test procedure in which a fluorescein dye that is injected into a vein in the arm travels to the retinal blood vessels. Special photographs allow the physician to see the vessels that may be affected and could tell how much of the retina/macula is affected.
How is retinal vein occlusion (RVO) treated?
  • Unfortunately, there is no way actually to unblock retinal veins. However, the doctor (your GP or hospital physician whom you may be referred to or are already under), can treat any health problems that seem to be related to the retinal vein occlusion. 
  • Focal laser therapy:This treatment provides laser to areas of swelling to reduce the fluid accumulation (oedema/swelling) in and around the macula (responsible for central vision). 
  • Pan-retinal photocoagulation therapy:This treatment is used when patients have abnormal new blood vessel formation following the retinal vein occlusion. 
  • Intravitreal injection of anti-VEGF drugs: These drugs target VEGF, which is an important growth factor that causes macular oedema/swelling. This medicine is delivered to your eye through a very slender needle. If you get this treatment, you may need multiple monthly injections. Before each injection, your eye will be numbed and cleaned with antiseptics. A few different anti-VEGF drugs are available i.e.
  • Ranibizumab (Lucentis)
  • Afiblercept (Eylea)
  • Bevacizumab (Avastin- unlicensed)

They vary in cost and in how often they need to be injected, so you may wish to discuss these issues with your eye care professional.

Intravitreal injection of corticosteroid drugs:

This drug combats the inflammatory components which lead to macular oedema/swelling. 

Your eye care specialist will help to you make the choices based on the severity and  prognosis of the condition.

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