Branch retinal artery occlusion, or BRAO, is a common disorder of a branch of the central retinal artery that leads to ischemia in the retina. While some people with branch retinal artery occlusion don’t experience symptoms, others do. There are a number of different causes of BRAO.
Branch retinal artery occlusion has two subtypes: permanent BRAO and transient BRAO. Permanent usually means more severe vision loss, while transient typically has a better prognosis. Some studies on central retinal artery occlusion indicate that ischemic retinal damage can occur within 97 minutes, causing long-term vision problems. Ischemic is a term to describe a restriction or reduction in blood flow somewhere in the body.
Prevalence of BRAO
In the United States, central retinal artery occlusions (CRAOs) account for just under 60 percent of acute retinal artery obstructions, while branch retinal artery occlusions are typically about 38 percent of cases.
For the most past, BRAO appears in the seventh decade of life. Among older patients, men seem to be 2.5 times more likely than women to have retinal emboli. This coincides with the higher rate of stroke in the male population.
Branch retinal artery occlusion related to embolic causes are rare in people under the age of 30. Cases that involve a person younger than 30 tend to be non-embolic. Embolic means that there is a lodging of a blood clot, fat globule, gas, air, or foreign material that can cause a blockage inside a blood vessel.
What Are the Causes of Branch Retinal Artery Occlusion?
So, what are the causes of retinal artery branch occlusion? The simple answer is any condition that decreases perfusion (passage of fluid) in a branch retinal artery. This is usually due to emboli, which are seen in over 60 percent of cases.
There are other branch retinal artery occlusion causes; however, they are less common. For instance, trauma and drug abuse. Non-embolic can also be related to cocaine abuse, as well as health issues such as inflammatory and infectious conditions.
List of embolic and non-embolic causes of branch retinal artery occlusion:
- Calcified cardiac valves
- Fat emboli due to long bone fractures
- Air emboli from a trauma or surgery
- Talc emboli from IV drug use
- Synthetic emboli from interventional procedures
- Sensorineural hearing loss
- Vasospasm secondary to migraines
- Cocaine abuse
- Behcet’s disease
- Herpes zoster, Lyme disease, giant cell arteritis – inflammatory/infectious diseases
- Susac syndrome – autoimmune condition impacting small blood vessels in the retina
- Autothrombosis – due to ruptured arteriolar microaneurysm
- Idiopathic – a syndrome that involves recurrent bouts of multiple branch retinal artery obstructions in otherwise healthy people.
Posterior uveitis has also been known to cause BRAO. It refers to inflammation in the back part of the uvea. The uvea is the tissue beneath the white of the eye.
Research shows that this type of inflammation can affect the retina. Additionally, branch retinal artery occlusion has also been seen following retrobulbar anesthesia for intraocular surgery. Vasospasms due to trauma, compression, or a reaction to anesthetics are possible theories.
Risk Factors of Branch Retinal Artery Occlusion
There are risk factors associated with BRAO. They include conditions that promote vascular narrowings, such as hypertension, carotid occlusive disease or atherosclerosis, coronary artery disease, and hypercholesterolemia.
Diabetes, transient ischemic attack, as well as smoking, have also been linked to branch retinal occlusion. It is believed that having a family history of blood clots or a clotting disorder can also increase your risk of BRAO.
Signs and Symptoms of BRAO
Branch retinal artery occlusion symptoms can include painless vision loss or blurring in one eye. Vision loss can be partial or it can be complete. There are some people who go through brief periods of vision loss just before BRAO develops. There are also patients who don’t experience any BRAO symptoms.
Retinal ischemia is usually detected by the presence of cotton wool spots and retinal whitening during an eye examination by a qualified doctor. In the case of BRAO, retinal whitening follows the course of a branch artery.
How is BRAO Diagnosed?
There are different procedures used in branch retinal artery occlusion diagnosis. The typical findings with BRAO include the onset of monocular visual loss that is often painless. A branch retinal artery occlusion fluorescein angiography can detect cotton wool spots in the branch of the retinal artery. Retinal ischemia may also be observed.
Aside from being permanent or transient, some people can get what is referred to as cilioretinal artery occlusion or CLRAO. Its blood supply comes from the posterior artery, not the central retinal artery.
Aside from the fluorescein angiography, the following may be used during diagnosis:
- Spectral Domain Optical Coherence Tomography (SD-OCT) – allows for close viewing of tissue structures.
- Carotid evaluation – helps in assessing cardiac valves and locating embolic sources of retinal occlusions.
- Magnetic Resonance Imaging (MRI) – used when certain conditions, such as Susac Syndrome are suspected.
The doctor will consider that the vision loss could be associated with conditions that present similar symptoms, including CRAO, ischemic optic neuropathy, and retinal detachment.
Treatment Methods for Branch Retinal Artery Occlusion
Branch retinal artery occlusion treatment will depend on the underlying cause. If you have been diagnosed, BRAO treatment includes regular visits with your ophthalmologist. In about 90 percent of patients, the cause can be identified, and proper branch retinal artery occlusion management can begin. The cause is managed either medically or surgically. Controlling risk factors may also have an impact on reducing the risk of BRAO symptoms.
Patients with branch retinal artery obstruction should receive a workup that includes the cerebrovascular and cardiovascular system. Depending on the outcome, carotid endarterectomy or anticoagulation may be suggested. If the source of the problem is not embolic, a lab workup for coagulopathies should be carried out.
In terms of surgical care, there have been a few cases where a procedure called surgical embolus excision has had a good outcome, but more study is needed to validate this type of surgery as a treatment for BRAO.
If you have been diagnosed with BRAO, it’s best to ask your doctor to explain each treatment for branch retinal artery occlusion in detail.
The prognosis of visual improvement after being diagnosed with BRAO usually relates to the visual clarity the person first had upon seeking medical assessment. With permanent BRAO, about 74 percent of patients initially have vision acuity (VA) of 20/40 or better while at follow-up 89 percent show 20/40. With transient BRAO, 100 percent of patients have 20/40 upon follow-up.
In general, people who suffer from branch retinal artery occlusion may maintain fair to good vision. Those who suffer from central artery occlusion can experience more serious vision loss, even with treatment.
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