Retinal vein occlusions

A retinal vein occlusion (RVO) is a blockage of a blood vessel in the retina. The retina is the lining of the back of the eye responsible for vision. The blockage can cause a build up of pressure in the vein, leading to bleeding and swelling of the retina. This may lead to reduced vision.

Retinal vein occlusions occur more commonly in people with a history of high blood pressure or diabetes.  They can be classified into central retinal vein occlusions (CRVO) in which the main central retinal vein has become blocked or branch retinal vein occlusions (BRVO) in which a smaller branch retinal vein has become blocked

What are the symptoms of a retinal vein occlusion?

 The commonest symptom is a sudden loss of vision. Occasionally, the loss of vision may be gradual.

How is it diagnosed?

A retinal vein occlusion has a typical appearance which can be diagnosed during an eye examination that includes assessment of the retina. The following tests may be needed to assess the severity and guide treatment decisions:

1. Photographs of the retina.
2. Optical coherence tomography scanning of the retina.
3. Fluorescein angiography.

What causes a retinal vein occlusion?

A central retinal vein occlusion (CRVO) is caused by a blood clot blocking the main vein in the retina.

A branch retinal vein occlusion (BRVO) is typically caused by a compression of a retinal vein by a thickened retinal artery.

The risk factors for a CRVO and BRVO are similar to those for a stroke or heart attack. Older age, high blood pressure, high cholesterol, diabetes, blood clotting disorders and smoking are all risk factors. They can also be caused by inflammatory eye conditions. Glacuoma is also a risk factor for CRVO.

Can the other eye become affected?

If one eye has been affected by a retinal vein occlusion, the risk of developing a retinal vein occlusion in the other eye is approximately 10%.

People at risk of a retinal vein occlusion should not smoke, should eat a healthy balanced diet, maintain a healthy weight and get regular exercise. People with high blood pressure or raised blood lipids should have these treated.

Treatment options for retinal vein occlusions

Treatment is not always needed because mild cases may improve by themselves. If vision is severely impaired or spontaneous improvement is thought to be unlikely the following treatments may be considered.

1. Laser treatment.

2. Injection of anti-VEGF agents. This includes bevacizumab (Avastin), ranibizumab (Lucentis) or aflibercept (Eylea).Anti-VEGF agents are medications designed to block the effects of a substance called vascular endothelial growth factor (called VEGF  for short) which causes abnormal blood vessels to grow and leak fluid in the retina.

   By blocking VEGF in the eye, these agents can often lead to improvement or stabilisation of vision. The most commonly used anti-VEGF agents are bevacizumab (trade name Avastin) and ranibizumab (trade name Lucentis). More recently a newer anti-VEGF agent has been developed called aflibercept (trade name Eylea). The safety of anti-VEGF agents Avastin and Lucentis when injected into the eye has been confirmed in multiple clinical trials.  

   Although there is a theoretical risk of side effects such as stroke or heart attack, there is no proven statistically significant evidence that the small dose of Avastin or Lucentis used when injected into the eye can cause similar side effects. Further research into this area is in progress. All eye injections carry a small risk of infection (less than 1 in 1000), bleeding or retinal detachment. These complications can often be effectively treated but can rarely lead to loss of vision.

3. Injection of steroids (Triamcinolone or Dexamethasone). Steroids can be injected into the eye to stop blood vessel growth and reduce swelling of the macula. This often leads to improvement or stabilisation of vision The risks of steroid injections in the eye include infection, retinal detachment, glaucoma and cataract. These complications can usually be treated, but may rarely lead to loss of vision.

4. Vitrectomy surgery. This is a form of keyhole surgery to remove the jelly (known as vitreous) inside the eye to improve its oxygen supply and remove any blood within the vitreous. Additional procedures can be performed in an attempt to improve blood flow within the retina.

5. Combination therapy. Depending upon individual circumstances, a combination of the above treatments may be recommended.

Dr Simon Chen

Dr Chen talks about the advances in vitrectomy surgery, as well as explaining injections.

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