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 is a high risk of stroke with this condition, so risk factors must be addressed Eye20 . MRI needed urgently
There are other causes which a are 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.
- Susuc syndrome BJO 20 ..other occlusions, deafness etc. "The characteristic ophthalmological feature in SS is the presence of recurrent multiple BRAO in the absence of intraocular inflammation. Yellow to yellow-white, non-refractile or refractile retinal arterial wall plaques (Gass plaques) found at midarteriolar segments not associated to bifurcations are commonly found in SS." JOI 2020 hearing loss "At least 50% of patients have visual disturbances as first clinical manifestation . Patients complain about reduced visual acuity, scintillating scotomas, photopsia or visual field defects. The characteristic fundoscopic findings in patients with SS are branch retinal artery occlusion or arterial narrowing and small punctuate yellow-white arterial wall plaques; these plaques are also called Gass plaques  and can resolve overtime [10, 11]. The findings in retinal fluorescein angiography (FA) are pathognomonic and show segmental arteriolar wall hyperfluorescence (AWH) with dye leakage in 96% of the patients , often occurring in a multifocal fashion and located distant to areas of branch retinal artery occlusion (BRAO). Moreover, non-perfused retinal arterioles or arterial luminal narrowing with a preserved downstream blood perfusion can be found in FA. This arterial mural staining indicating an impaired integrity of the arterial or arteriolar wall may be found unilaterally or bilaterally . A progression of the AWH into BRAO has been documented in some cases but it is unclear why some AWH result in BRAO and others do not. It is important to know that AWH and arterial luminal narrowing in FA can even be found in a normal appearing fundus . Indocyanine green angiography (ICGA) is showing hypofluorescence in the areas of retinal infarction and is also showing retinal vessel abnormality while choroidal circulation appears as normal . Optical coherence tomography (OCT) has recently become a valuable diagnostic tool. In a case series, 68% of SS eyes showed significantly reduced average retinal nerve fibre layer thickness (RNFLT)). Characteristic is the very distinct pattern of patchy thinning of the inner retina while the outer retina remains normal reflecting arterial distribution . In OCT sectors with severe inner retinal thinning are located adjacent to normal appearing sectors [12, 14]. OCT provides complementary diagnostic information to FA especially in chronic or later stages of the disease."
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.
TIA (this will include retinal artery occlusion)
- NEJM 20
- Aspirin 300mg stat and 75mg a day
- clopidrogel 300mg stat and 75mg a day for the first 21 days
- aspirin long term disputed
- referral to TIA clinic