Vein occlusion is a disease of the retina most frequent after diabetic retinopathy.
When a vein occlusion occurs, blood can no longer evacuate normally out of the eye: this results in a slowing down of blood circulation and high pressure in the veins. In the back of the eye, these phenomena turn into a dilation of the veins and appearance of haemorrhages.
An occlusion may affect a sector of the retina, this is then a vein branch occlusion. When the whole retina is affected, it is known as an occlusion of the retina’s central vein .
There are two forms of central vein occlusions: non-ischemic occlusions and ischemic occlusions.
Patients experience a drop in visual acuity but of variable degree.
Vein occlusions can occur at any age, but usually affect people over 60 years of age.
The cause of vein occlusions is uncertain. There are however factors that favour it: cardiovascular diseases, diabetes, hypercholesterolemia or other blood anomalies.
High blood pressure is frequently found associated with occlusions of the retina’s central vein, without the relationships between the two diseases being properly understood.
Glaucoma is also frequently associated with vein occlusions.
Half of vein occlusions regain normal visual acuity. Either the occluded vein reopens spontaneously, or vessels called “collateral vessels” develop to overcome the obstruction.
Unfortunately, ischemic occlusions have a far less positive prognosis. Remember that ischemia is a decrease in arterial blood to an organ. This type of occlusion generally only allows poor recovery of sight with risks of complications like neovascularisation. This means that new vessels form on the retina with intravitreous haemorrhage. On the iris, the new vessels may obstruct the trabeculum (filtration system for the aqueous humour outside the eye) and this leads to high ocular pressure which is a source of neovascular glaucoma.
Most often, an ophthalmologist diagnoses it by examining the back of the eye. Examination of the back of the eye shows retinal haemorrhages, a tortuosity of veins and an optic nerve oedema.
Additional examinations are most often limited to photos of the back of the eye, and sometime an angiography (injection of a fluorescent product into the arm veins in order to see the retina’s vessels better).
There are some preventive measures to be taken to protect the other eye.