What is Amaurosis Fugax (Transient Visual Loss (TVL))?
Amaurosis fugax is a term often used to describe short-term vision loss. More specifically, it’s used in the medical field to talk about any cause of temporary vision loss in one eye. For this discussion, we’re only using amaurosis fugax to refer to temporary vision loss in one eye that happens because of small blood clots resulting from the internal carotid arterial system, the major arteries that supply blood to the head and neck.
This condition is pretty rare in children and is usually due to an innocent reason. However, in adults, most of the time, it’s caused by fatty deposits coming from the split in the carotid artery, often due to hardening of the arteries.
What Causes Amaurosis Fugax (Transient Visual Loss (TVL))?
Amaurosis fugax is caused by a blockage or narrowing of the internal carotid artery, which provides blood to your brain and face. This condition can happen due to a blood clot from this artery, or from low blood flow as a result of the narrowing of the artery. These issues are what lie beneath this condition.
The ocular ischemic syndrome is a result of chronic low blood flow caused by a blockage of one or both carotid arteries. When these arteries are blocked, it can affect the eye and cause a bunch of symptoms.
Risk Factors and Frequency for Amaurosis Fugax (Transient Visual Loss (TVL))
Amaurosis fugax, a temporary loss of vision, typically affects people over 50 who have various health issues related to the blood vessels. These issues may include high blood pressure, high cholesterol, smoking, previous short-lived strokes (known as transient ischemic attacks or TIAs), and cramping pain in the legs due to poor circulation (known as claudication). Patients with amaurosis fugax have an estimated 2% chance of stroke per year, and if there are retinal emboli (blood clots in the eye), the risk increases to 3% per year.
Several risk factors make people more likely to develop amaurosis fugax:
- Diabetes
- Heart disease
- Smoking
- High blood pressure (hypertension)
- Excessively high fat levels in the blood (hyperlipidemia)
- Advanced age
- Cocaine use
Signs and Symptoms of Amaurosis Fugax (Transient Visual Loss (TVL))
Some people may suddenly lose vision in one eye, a condition which can last from 2 to 30 minutes. The vision loss could affect the whole visual field or only a part of it. People often describe it as a “curtain coming down” in front of their eye or as a generalized darkening or shadow. These episodes tend to resolve on their own. People can experience just one episode or multiple ones. If a person over 60 years old keeps having these episodes, it could be a sign of a condition called giant cell arteritis, and more tests should be done to make sure.
Some patients may have signs of bits of fat called cholesterol plaques in the retina, called Hollenhorst plaques. Depending on the severity of the damage to the retina from lack of blood flow, this could result in blockage of the central retinal artery or branches of the retinal artery.
In some patients, especially those with a condition called ocular ischemic syndrome, exposure to bright light can trigger these episodes. This happens because the carotid artery, the main blood supplier to the eye, is severely blocked. This causes reduced blood flow to the retina, and when in bright light, the demand for blood increases, which can lead to blurry or decreased vision. Once the eye adjusts, vision usually returns to normal.
People with ocular ischemic syndrome generally experience blurry vision that can come and go. As the disease worsens, the disturbed vision progressively declines. The affected eye might show signs of inflammation, and there may be little inflammation in the front part of the eye. Eye pressure may be low or normal due to decreased blood supply to the ciliary body, the part of the eye that helps produce fluid. An examination of the back of the eye can show changes in the veins and arteries in the retina, along with small, dot-like hemorrhages. A telltale sign of this condition is eye pain that typically feels better when lying down. This happens because of damage to the nerves supplying feeling to the eye and orbit caused by lack of blood supply.
Testing for Amaurosis Fugax (Transient Visual Loss (TVL))
If you’re experiencing symptoms of sudden temporary vision loss, known as amaurosis fugax, your doctor will likely assess you for potential risk factors related to blood flow. These include high blood pressure, diabetes, high cholesterol, heart disease, and tobacco usage.
A thorough physical check-up will also be conducted, including a full eye examination with specialized techniques to look at the back of your eye, listening to your carotid arteries (large blood vessels in the neck that supply blood to the brain and head) and heart sounds.
The doctor will also order several blood tests, which may include a complete blood count to assess your overall health, blood glucose level test to monitor any signs of diabetes, lipid profile to measure fats and fatty substances in your blood, and several others to check the time it takes for your blood to clot, levels of inflammation, and other factors.
A Carotid Doppler test, which uses ultrasound waves to check the blood flow and identify any blockages in the carotid arteries, is another non-invasive procedure you might undergo. Additionally, magnetic resonance angiography (a type of MRI scan) and computed tomography angiography (a type of CT scan) can be used to further evaluate the openness of the internal carotid arteries.
To check for any irregular heart rhythms or potential blood clots in the heart, an electrocardiogram, continuous heart monitoring known as Holter monitoring, or in some cases, transesophageal echocardiography (an ultrasound scan of the heart taken from inside your esophagus) might be performed.
Finally, neuroimaging studies that take pictures of the brain are usually done to rule out other causes of vision loss. A CT scan could also be used to ensure there isn’t a bleed in your brain.
Treatment Options for Amaurosis Fugax (Transient Visual Loss (TVL))
The first step in treating conditions related to blood flow issues, such as high blood pressure, diabetes, and high cholesterol, is to manage these underlying health problems.
According to two large research studies, the North American Symptomatic Carotid Endarterectomy Trial (NASCET) and the European Carotid Surgery Trial (ECST), a surgical procedure called endarterectomy can reduce the risk of stroke in patients experiencing symptoms and who have more than 70% blockage in the carotid artery, a major blood vessel in the neck. However, these studies didn’t specifically look at one type of event known as “ocular TIAs” – temporary disruptions of blood flow to the eyes.
The NASCET study also found that patients who had hemispheric TIAs (temporary disruptions of blood flow to the brain) were more likely to have a stroke within two years compared to those with ocular TIAs (44% versus 17%), and none of the patients with ocular TIAs experienced a major stroke, which is defined as one causing disability for more than 90 days. Despite these differences, both groups had similar levels of blockage in the carotid artery – about 83%.
Considering these findings, healthcare providers need to decide whether the potential risks associated with endarterectomy (including the risks of death and preoperative stroke) outweigh the benefits, especially given the relatively low risk of stroke in patients with ocular TIAs when they’re treated with blood thinners alone, such as aspirin, warfarin or clopidogrel.
It’s worth noting that the above-mentioned studies evaluated endarterectomy, an open surgical procedure, but a procedure called carotid stenting has since become common. Carotid stenting involves placing a small mesh tube in the carotid artery to improve blood flow, and this treatment has been shown to be similar in effectiveness to endarterectomy, with comparable low risks of death, stroke, and heart attack in patients who aren’t showing symptoms but have severe blockages in the carotid artery.
In regards to ocular ischemic syndrome, a condition that can cause vision problems due to reduced blood flow to the eyes, treatment aims to reduce the drive of oxygen to the eye to decrease the formation of new blood vessels. Approaches to achieving this may include panretinal photocoagulation, a laser treatment used to create tiny burns in the retina, or injections of anti-vascular endothelial growth factor (VEGF) drugs into the eye, which can halt the growth of new blood vessels.
What else can Amaurosis Fugax (Transient Visual Loss (TVL)) be?
If someone is losing vision in one eye, the doctors need to consider a variety of possible causes. These might include:
- Blockage in the central retinal artery or vein
- Giant cell arteritis (an inflammation of the arteries)
- Multiple sclerosis (a condition affecting the central nervous system)
- Papilledema (swelling of the optic nerve due to increased pressure in or around the brain)
- Epilepsy (a neurological disorder causing seizures)
- Sickle cell anemia (a group of genetic disorders that affect the red blood cells)
What to expect with Amaurosis Fugax (Transient Visual Loss (TVL))
If ‘amaurosis fugax’ – a medical term referring to a temporary loss of vision – isn’t spotted or treated in time, it could put the patient at risk of a major stroke in the future. The scary fact is that most patients with significant plaques in the carotid artery – which is the large artery in the neck that supplies blood to the brain – could develop a major stroke within the forthcoming 12 months if left untreated.
A procedure called ‘carotid endarterectomy’ – a surgery to remove plaques from the carotid artery – offers good prospects of improvement, but doesn’t eliminate the risk of heart-related complications completely. Sadly, the outlook for patients who do end up suffering a stroke tends to be more uncertain.
Possible Complications When Diagnosed with Amaurosis Fugax (Transient Visual Loss (TVL))
The primary complications of a condition called amaurosis fugax can be quite serious.
- Stroke
- Death
- Negative heart-related events
