The retina is a thin layer of light sensitive cells, which lines the back of the eye. The eye is like a camera with a lens at the front and a light sensitive film (retina) at the back. The retina has blood vessels in it, which fan out from the centre to the edge. The retinal arteries bring blood to nourish the retina and the retinal veins carry waste products back out of the eye.
If the flow of blood in the veins stops or slows for any reason, spots of blood and protein may leak out of the vein and into the retina and this can affect vision. The symptoms are variable and range from mild to severe visual loss depending on the size and site of the blocked vein. Leakage of fluid from the blocked vein causes swelling of the surrounding retina thus blurring the vision. Sometimes the flow of blood stops completely and then parts of the retina die so that vision is severely affected.
Several factors can cause an occlusion in the retinal vein:
Age
Anything that makes the blood too thick or sticky e.g. smoking cigarettes
High blood pressure
High cholesterol or lipids
Diabetes
Inflammation in the eye
New blood vessels may form inside your eye and may cause further problems in the eye:
Vitreous haemorrhage: new blood vessels are fragile and may bleed into the vitreous jelly of the eye, causing sudden further loss of vision.
Neovascular (Rubeotic) Glaucoma: the new blood vessels grow on the coloured iris at the front of the eye and around the fluid drainage channels resulting in an increase in the eye pressure. This can result in the eye becoming red, painful, and more sight may be lost.
Everyone will need blood tests to look for the cause of the vein occlusion.
All patients will have their eye pressures checked and their eyes examined to look for risk factors for vein occlusion or complications from it.
Some patients may need a fluorescein angiogram, which is a test to look at the blood flow though the retina.
Some patients may need an OCT to show how much retinal swelling is present.
Unfortunately there is no treatment that will restore vision in the affected eye.
It is very important to prevent another episode of vein blockage in either eye so your blood pressure will be measured and you will be asked to have blood tests to identify any cause of the vein occlusion.
If new blood vessels are growing on the iris or retina then laser treatment is necessary to try and help shrink these vessels.
If there is swelling of the central retina (macula) then laser treatment or frequent injections of medication into the eye (performed in the clinic under local anaesthesia) may be required to reduce the swelling to preserve the vision.
