Central retinal artery
The central retinal artery is the main artery bringing blood to the retina at the back of the eye.
Branch retinal arteriole
As the central retinal artery enters the eye, it splits into branches.
Blocked central retinal artery or branch retinal arteriole
The central or branch retinal arteriole may block. If they do, then blood cannot reach the retina, and after 3 hours without blood the retina becomes permanently damaged. This is termed a 'central' or 'branch retinal artery occlusion'
Causes of the blockage/occlusion
The blockage in older patients has two common causes.
- A common cause is a clot from the neck: the carotid artery surface in the neck becomes rough (atherosclerosis) and tiny clots break off, a travel up to the eye and block the central or one of the branch retinal arteries.
- Another common cause is an embolus from the heart. This may occur if the heart beat is irregular, that is atrial fibrillation. 2015
There are other causes which a re less common.
In younger patients.
- There may have been neck injury, and this may damage the artery.
- There may be a hole in the heart ' a patent foramen ovale'. This will be a very rare cause.
In younger patients.
- Older patients may have giant cell arteritis, a condition that causes inflammation of arteries in the elderly. If a clot is visible in the retina, this will NOT be the cause.
- Sometimes the clot is clearly visible when the retina is examined, but often it is not visible.
- If the condition has been present less than 3 hours, then it may be possible to move the clot.
There are various measures that may occasionally move the clot see.
- More recently, a paracentesis...an injection into the front chamber of the eye to withdraw some aqueous fluid..may lower the pressure in the eye and improve the blood flow. paracentesis
- In practice, most patients wake up in the morning with poor sight in one eye, and so the blockage will have occurred more than 3 hours previously, and this treatment will not be effective.
- Even if there is no treatment that will help the affected eye, it is helpful to find the cause so as to prevent a problem to the other eye, or even a stroke.
- It is important to measure the risk of strokes.
- Blood pressure control and cholesterol treatment will be needed in the longer term. In the short term, patients are usually referred to a TIA clinic. If there is atrial fibrillation is present, then one of the new anticoagulant drugs may be needed.