Retinal Vein Occlusion
What is retinal vein occlusion?
The word ‘macula’ refers to centre of the retina. Being central, macula provides detailed sharp vision, especially near vision such as needed for reading, knitting etc.
Retinal Vein Occlusion FAQ’s
Why does retinal vein occlusion occur?
Retinal vein occlusion occurs when one of these veins is blocked by a blood clot that prevents the blood draining from the retina. This causes blood and fluid to leak into the retinal tissue. The fluid leakage predominantly affects the macula.
The exact cause for this is not known. It is thought that the pressure from the retinal artery crossing over the vein may cause the clot to form. The common risk factors for developing retinal vein occlusion are high blood pressure, diabetes, high cholesterol, smoking and glaucoma. Less commonly, patients suffering from rare conditions affecting the blood (Myeloma) or inflammation of the blood vessels at the back of the eye (Behcet’s disease, Sarcoidosis etc) can develop RVO.
What are the types?
1. Central Retinal Vein Occlusion (CRVO) – the blockage occurs in the main retinal vein causing damage to the entire retina.
2. Branch Retinal Vein Occlusion (BRVO) – the blockage occurs in one of the branches of the main vein causing damage to the part of the retina in the area drained by that vein.
Why is sight affected?
1. Swelling of the macula (Macular Oedema): This is the most common cause. It means waterlogging of the macula caused by leakage of fluid. Since the macula is responsible for detailed sharp vision, macular oedema causes blurred vision.
2. New blood vessels growth (Neovascularisation): Occasionally fragile and leaky blood vessels can grow as a consequence of the vein occlusion. These abnormal blood vessels may bleed inside the eye, causing what is called a vitreous haemorrhage, or put the pressure up in the eye causing a condition called rubeotic glaucoma.
What tests are required?
1. Fundus fluorescein angiography – in this test a dye is injected in the arm and photographs are taken of the dye as it passes through the blood vessels at the back of your eye.
2. Swept-source OCT retinal scan – It is a test which uses a light beam to create an ultra-high-definition scan of picture of the macula. It helps confirm the diagnosis of macular oedema and monitor progress once treatment is commenced.
What are the treatment options for macular oedema?
1. Observation: In a small proportion of patients, macular oedema can resolve spontaneously.
2. Laser treatment to macula: This involves applying laser burns to the macular region. Laser treatment only works in some cases of BRVO but not in CRVO. It is carried out as an outpatient procedure.
3. Injection of anti-vascular endothelial growth factor (anti-VEGF) drugs: The anti-VEGF drugs work on leaky blood vessels to help reduce fluid in the macula. Lucentis, Eylea and Avastin are the drugs available in this category. Injections are given in an outpatient setting under local anaesthesia. One injection is given every month for the first three months.
Thereafter monthly assessments continue during which further injections may be needed.
4. Injection of Ozurdex: Ozurdex is a very small steroid implant, which is injected in the eye under local anaesthesia. The effect of treatment lasts 3-4 months and it can be repeated thereafter.
Which treatment is most effective?
In BRVO the success rate of improving sight is approximately 60% while in CRVO the success rate is approximately 45%.