What is retinal vein occlusion?
A retinal vein occlusion is a common cause of sudden, painless reduction and vision. It occurs when a blockage, often caused by a blood clot, forms in a retinal vein. The retina is the thin membrane at the back of the eye that receives light and sends pictures of what the eye sees to the brain. Its blood supply is drained by tiny veins. Blockage of one of the veins draining blood out of the eye causes blood and other fluids to leak into the retina, resulting in bruising and swelling, as well as depriving the retina of oxygen. This affects the light receptor cells in the retina, which results in reduced vision
There are three types of Retinal Vein Occlusion (RVO):
- Branch Retinal Vein Occlusion (BRVO), caused by an obstruction to one of the smaller branch veins
- Central Retinal Vein Occlusion (CRVO), caused by an obstruction to the main vein draining blood from the retina
- Hemi-Retinal Vein Occlusion (HRVO), caused by an obstruction to one of the two main branches of the central vein
A RVO is most likely to happen in older people, people with high blood pressure, a history of heart attack or stroke, diabetes, and in glaucoma, as well as in some rarer conditions. How it affects the vision in the long term depends on which vessel is affected and whether this reduces the retina’s oxygen supply (‘ischaemic’ type) or does not (‘non-ischaemic’ type). The outlook for vision is better in the non-ischaemic type. In the ischaemic type, new blood vessels grow into the retina and the iris, which sometimes results in glaucoma. This can be treated by closing the new vessels with the laser.
How is retinal vein occlusion managed?
The optometrist will refer the patient to an ophthalmologist (specialist eye doctor) for an urgent appointment. In addition, urgent referral to the patient’s GP may be arranged for medical management and investigation of any underlying condition.
The main complication of RVO that affects vision is the build-up of fluid at the macula (the most sensitive part of the retina which gives the eye detailed colour vision). Hospital treatment usually includes injections of Anti-Vascular Endothelial Growth Factor (anti-VEGF) or steroids, which has been shown to be safe and effective.