(Retinal Vein Occlusion) (Retinal Artery Occlusion)
A blockage in either a retinal vein or artery is medically known as a 'retinal vessel occlusion'.
The main cause of a retinal artery occlusion is atherosclerosis (sometimes called hardening or thinning of the arteries and veins)
There are a number of common risk factors for this thinning of arteries and veins. The main risk factors are:
Age - most retinal vessel occlusions happen in people over 65
High blood pressure
High cholesterol levels
Although nothing can be done about our age, all the other risk factors can be controlled. Regular visits to your GP to diagnose any circulation problems like high blood pressure and cholesterol levels, good diabetic control, a healthy diet and stopping smoking can all help to reduce the risk of experiencing a retinal vessel occlusion.
If the arteries become blocked then the amount of sight that is affected varies according to the location of the blockage.
When one of the veins becomes blocked then the used blood cannot drain away properly. This causes the blood to 'back up' in the system. This blocking and pooling of blood can cause the area to swell and also causes areas of haemorrhage (bleeding). These areas of swelling and backed up blood damage the cells of the retina and therefore damage sight.
Both types of retinal vessel occlusion cause a painless loss of vision.
In an artery occlusion this loss of vision usually happens very suddenly with little or no warning. Some people may experience short periods of sight loss (amaurosis fugax) before the sight loss becomes permanent.
In a vein occlusion sight loss may be gradual, you may notice that your sight dims over a period of time.
Retinal artery occlusion. Unfortunately there is little treatment available for retinal artery occlusions because the cells on the retina are very sensitive to a lack of blood supply. In some people the blockage that causes the first sight loss may become dislodged and if the blood supply is started again then some improvement in vision may be seen. Most people however have permanent changes in their vision.
Retinal vein occlusion. The sight loss can sometimes improve on its own. Because the blood 'backing-up' causes swelling and bleeding, sometimes when this clears up, sight can improve a little. In a few cases, a laser can be used to help control the swelling and this can mean that sight improves a little.
If new blood vessels do start to grow the laser is used to stop more damage occurring so although no sight is restored the likelihood of losing more sight is reduced.
A treatment called Ozurdex has recently been licensed for use in central macular oedema caused by retinal vein occlusion. This treatment involves injecting a small capsule of a steroid into the eye. This capsule stays in the eye and slowly releases the steroid.
Early reports that this treatment is effective at reducing the swelling caused by the retinal vein occlusion and improving vision in the long term.
Retinal vessel occlusions are fairly common but there are ways of avoiding the chances of having one. Regular checks with the GP can discover whether you may be at risk. Drugs to control high blood and cholesterol levels can help along with a good diet, low in fat and saturated fat, stopping smoking and moderate exercise can all help avoid circulation problems that can be the root of the retinal occlusion.
If a lot of sight in one eye is affected quite badly then, for a period of time, people may feel slightly unbalanced. When sight in one eye is affected it can affect our depth perception. You may find that you have trouble judging distances, how high a step is or how far away a table is. With time you should be able to judge these distances better but you should take care in the first couple of months.
You may be concerned about driving following loss of sight in one eye, however it is legal to drive with sight like this. As long as your sight in the other eye is good enough to see a number plate at 20.5 metres wearing any glasses that you may need and you have 120 degrees in your field of vision you will be legally able to drive.
Your optician or ophthalmologist will be able to let you know if your sight is good enough for driving.