A retinal vein occlusion is a medical term to describe a blockage of one of the blood vessels of the retina. Being such a metabolically active tissue, the retina requires a high oxygen and energy demand. This makes retinal vein occlusions a potential medical emergency with a risk of permanent vision loss. Keep reading to learn more about treatment for this vision-threatening retinal condition.
What is a Retinal Vein Occlusion?
Any occlusion (blockage) of a retinal vein is called retinal vein occlusion. This can occur in the main vein of the retina, which is then known as a central retinal vein occlusion (CRVO), or in one of the smaller offshoot retinal veins, which is then termed a branch retinal vein occlusion (BRVO). There are also even smaller branches of the retinal vein network known as retinal capillaries.
The retinal vein network is responsible for taking away deoxygenated blood from the retina back to the heart and lungs to be replenished with oxygen. Retinal arteries are the blood vessels that carry blood back from the lungs to the retina, restocked with vital oxygen and nutrients.
Causes of Retinal Vein Occlusion
The causes of retinal vein occlusions tend to be due to a blood clot becoming trapped in the blood vessel. This blockage stops the flow of blood throughout the network of retinal blood vessels.
Central Retinal Vein Occlusion
In a central retinal vein occlusion, the location of this blood clot is often around where the optic nerve enters the eye. In some cases, the clot can become lodged within the retinal vein after it’s exited the eyeball.
Branch Retinal Vein Occlusion
During a branch retinal vein occlusion (BRVO), a clot is more likely to form at the point where the retinal vein crosses over a retinal artery. Occlusion of branch retinal veins is up to seven times more frequent compared to blockages of the central retinal vein.
Do Retinal Vein Occlusions Cause Vision Loss?
Vision loss from a retinal vein occlusion, whether in the central or branch vessel, is due to one or both of two possible complications.
Macular oedema (also spelled as macular edema) refers to swelling of the macula area. The macula is the part of the retina you use for central vision. Damage to these nerve cells from macular oedema can result in significant vision loss. Because we use our central vision for so many crucial tasks, such as recognising faces, reading, and writing, vision impairment from macular oedema can be particularly devastating.
This is the medical term for lack of oxygen to the retinal nerve cells, which can affect a wide area of the retina or a small area, depending on the location of the retinal vein occlusion.
If the retina is experiencing low oxygen, it often responds by growing new blood vessels. The problem is that these abnormal blood vessels can be subject to fluid leakage, which contributes to macular edema. The other complication is if these new blood vessels grow into the structures at the front of the eye, it can induce elevated eye pressure and subsequent damage to the optic nerve in a disease called neovascular glaucoma.
Retinal Vein Occlusion Treatment
Timely treatment can help to maintain vision; however, despite treatment, it is possible to experience permanent damage and some degree of long-term vision loss.
The decision on how best to treat a vein occlusion is based on the location and size of the blockage. Your eye doctor will perform a thorough assessment of your retina and any other relevant health problems. Tests can include imaging scans such as optical coherence tomography, which is useful for visualising the location and degree of macular swelling, and another test called fluorescein angiography, which shows a map of the retinal blood vessels, including areas of leaking fluid or retinal ischaemia.
The first-line treatment for macular edema caused by a retinal vein occlusion is with a therapy called anti-VEGF injections. Anti-VEGF therapy involves intravitreal injection (that is, injected directly into the eyeball) of a drug known as anti-vascular endothelial growth factor, which inhibits the growth of abnormal new blood vessels.
Anti-VEGF injections are also used to treat the swelling of the macula in macular edema.
These injections will often need to be repeated monthly for at least a few months. If required, you may need further injections at regular intervals to maintain the effects of the therapy.
In some cases, laser treatment will be the most appropriate for treating the complications of a retinal vein occlusion.
Focal Laser Therapy
Focal laser therapy involves the use of a laser tool to seal off blood vessels close to the macula to prevent fluid leaking. Essentially, the treated blood vessels are cauterised closed.
Laser surgery can be used if new blood vessels are beginning to develop in the retina due to ischaemia. Using a laser to create tiny burns in the retina reduces its oxygen demand and minimises the trigger to grow extra vessels.
Risk Factors and Prevention
Although it’s not possible to make yourself immune to ever experiencing a retinal vein occlusion, you can minimise your likelihood by understanding and managing your risk factors.
The risk factors for retinal vein occlusion are similar to those for other cardiovascular diseases, such as heart attack and stroke. They include:
- Older age
- High blood pressure (hypertension)
- High cholesterol
- Being overweight
Though you can’t do much about ageing, taking steps to control your other risk factors can help to reduce your risk of vision loss due to retinal vein occlusion.
There is also some suggestion that the contraceptive pill can contribute to an elevated risk of retinal vein occlusion, though this has been rarely reported. Speak to your doctor if you have any concerns.
Note: Any surgical or invasive procedure carries risks. Before proceeding, you should seek a second opinion from an appropriately qualified health practitioner.
Retinal Vein Occlusion.
Retinal vein occlusion.
What is Retinal Vein Occlusion.