It is a temporary loss of vision in one or both eyes, its name comes from the Latin “fugax” that translates fleeting or fast, from the Greek “amaurosis” which means darkness.
The experience of Amaurosis Fugaz is classically described as a temporary loss of vision in one eye or in other cases, in both eyes, the patient experiences as a “black curtain” that covers the area of vision vertically.
This brief altitudinal visual loss is actually very rare. In one study, only 23% of patients with transient monocular vision loss experienced the classic “curtain” or “shadow” that fell on their vision.
Other descriptions of this experience involve blindness in only one eye, attenuation, fogging or blurring.
Generally this “blindness” only lasts a moment, usually a few seconds, some patients have experienced loss of vision for a few minutes or even a few hours.
The duration depends on the cause of the loss of vision. Obscured vision due to papilledema may only last for a few seconds, whereas a severely atherosclerotic carotid artery may be associated with a duration of one to ten minutes.
Certainly, there may be additional symptoms with Amaurosis Fugaz, and those findings will depend on the cause of the transient loss of monocular vision.
Causes of the Amaurosis Fugaz
Before 1990, Amaurosis Fugaz could, “clinically”, be divided into four complexes of identifiable symptoms, each with its underlying pathology:
In 1990, the Amaurosis Fugaz causes were refined by the Amaurosis Fugaz Study Group, which has defined five different classes of transient monocular blindness based on its supposed cause:
- Idiopathic or no identified cause.
With respect to the underlying pathology to these causes (except idiopathic), some of the most frequent causes include:
- Atheromatous disease of the internal or ophthalmic carotid artery.
- The temporal vasospasm.
- Neuropathies of the eye.
- Arteritis or giant cell vasculitis.
- Closed angle glaucoma.
- Increase of the internal pressure of the skull.
- Orbital compression disease.
- Phenomenon of coronary robbery.
- Hyperviscosity or blood hypercoagulability.
Embolic and hemodynamic origin
With respect to embolic and hemodynamic causes, this transient monocular visual loss occurs ultimately due to a temporary reduction of the retinal artery, the ophthalmic artery or the blood flow of the ciliary artery, resulting in a decrease in the retinal circulation that in turn it causes retinal hypoxia.
Although, more frequently, the emboli that cause the Amaurosis Fugaz are described as coming from an atherosclerotic carotid artery, any embolism that arises from the vasculature that precedes the retinal artery, the ophthalmic artery or the ciliary arteries can cause this monocular blindness transient
Atherosclerotic carotid artery : Amaurosis Fugaz could also present as a transient ischemic attack, similar to a stroke, where a plunger obstructs the retinal artery preventing light from passing.
It can also obstruct the ophthalmic artery, causing the flow of blood to decrease to the ipsilateral retina. The most common source of these atheroemboli is an atherosclerotic carotid artery.
A severely obstructed carotid artery can also cause Amaurosis Fugaz due to its stenosis of blood flow, which leads to ischemia when the retina is exposed to bright light.
Unilateral visual loss in bright light may indicate occlusive disease of the ipsilateral carotid artery and may reflect the inability of the borderline circulation to maintain the increased retinal metabolic activity associated with exposure to bright light.
Atherosclerotic ophthalmic artery : it will present similarly to an atherosclerotic internal carotid artery.
Cardiac embolism : thrombotic emboli arising from the heart can also cause luminal obstruction of the retinal, ophthalmic and / or ciliary arteries, causing decreased blood flow to the ipsilateral retina; examples are those that arise due to:
- Atrial fibrillation
- Valvular abnormalities that include post-rheumatic valve disease, mitral valve prolapse, and a bicuspid aortic valve.
- Auricular myxomas
Temporary vasospasm : which leads to decreased blood flow may be a cause of Amaurosis Fugaz. In general, these episodes are brief, do not last more than five minutes and have been related to the exercise.
These vasospastic episodes are not restricted to young, healthy individuals. The observations suggest that a systemic hemodynamic challenge causes the release of vasospastic substance in the retinal vasculature of an eye.
Giant cell arteritis : Giant cell arteritis can produce granulomatous inflammation in the central artery of the retina and in the posterior ciliary arteries of the eye, resulting in partial or complete occlusion.
What causes a decrease in blood flow that manifests as Amaurosis Fugaz. Commonly, Amaurosis Fugaz caused by giant cell arteritis may be associated with jaw claudication and headache.
However, it is not uncommon for these patients to have no other symptoms. An exhaustive review found an incidence of two to nineteen percent of Amaurosis Fugaz among these patients.
Malignant hypertension : can cause ischemia of the optic nerve head leading to transient monocular visual loss.
Iatrogenic : Amaurosis Fugaz may present as a complication after carotid endarterectomy, carotid angiography, cardiac catheterization and cardiac bypass.
Eye causes include:
- Iritis : inflammation of the medial layer of the eye.
- Keratitis: inflammation of a translucent tissue in the cornea.
- Blepharitis : inflammation of the eyelid.
- Drusen optic disk: muscle degeneration.
- Posterior vitreous detachment: it is associated with age.
- Closed angle glaucoma: pain and blindness.
- Transient elevation of intraocular pressure: ocular hypertension.
- Intraocular hemorrhage: bleeding inside the eye.
- Coloboma: iris of the malformed eye.
- Myopia: blurred vision.
- Hemangioma orbital: tumor benigno.
- Osteoma orbital: tumor benigno.
- Keratoconjunctivitis sicca: disease that causes red eyes and inflammation.
Neurological causes include:
- Optic neuritis
- Optical compressive neuropathies.
- Papilledema : the underlying mechanism for visual obscurations in all these patients seems to be transient ischemia of the optic nerve head as a consequence of the increase in tissue pressure.
Axonal swelling, intraneural masses, and increased interstitial fluid influx may contribute to increased tissue pressure at the head of the optic nerve.
The resulting reduction in perfusion pressure makes the small low-pressure vessels supplying the head of the optic nerve vulnerable.
Brief fluctuations in intracranial or systemic blood pressure may cause transient loss of function in the eyes. In general, this transient visual loss is also associated with headache and swelling of the optic disc.
- Intracranial hypertension.
- Intracranial tumor
Despite the temporary nature of vision loss, those who experience Amaurosis Fugaz are advised to consult a doctor immediately, as it is a symptom that can signal serious vascular events, including stroke .
Due to the short interval between the transient event and a cerebrovascular accident or blindness due to temporal arteritis, treatment for transient monocular blindness should be performed without delay.
A diagnostic evaluation should start with the patient’s history, followed by a physical examination, with special importance for the ophthalmic examination with respect to the signs of ocular ischemia.
When Amaurosis Fugaz is investigated, an ophthalmological consultation is absolutely justified if it is available.
Laboratory tests should also be ordered to investigate some of the most common systemic causes, including a complete blood count, erythrocyte sedimentation rate, lipid panel, and blood glucose level.
If a particular cause is suspected based on history and physical condition, relevant additional laboratories should be ordered.
If the laboratory tests are abnormal, it is likely that there is a process of systemic disease and, if the ophthalmological examination is abnormal, an eye disease is likely to occur.
However, in the case that both investigation routes yield normal results or an inadequate explanation, noninvasive duplex sonographic studies are recommended to identify carotid artery disease.
Most episodes of Amaurosis Fugaz are the result of stenosis of the ipsilateral carotid artery.
That being the case, the researchers found the best way to evaluate these episodes of vision loss and concluded that for patients who are between 36 and 74 years of age, a duplex scan of the carotid artery should be performed.
Since this research is more likely to provide useful information than an extensive cardiac exam (24-hour Holter monitoring and precordial echocardiography).
In addition, concomitant computed tomography or magnetic resonance imaging is also recommended to investigate the presence of a “clinically silent stroke”.
If the results of ultrasound and intracranial imaging are normal, renewed diagnostic efforts can be made, during which fluorescein angiography is an appropriate consideration.
If the analyzes reveal a process of systemic disease, targeted therapies should be initiated to treat that underlying cause.
If the Amaurosis Fugaz is caused by an atherosclerotic lesion, aspirin is indicated and it is considered a carotid endarterectomy depending on the location and degree of the stenosis.
In general, if the carotid artery is still patent, the greater the stenosis, the greater the indication for endarterectomy.
If left untreated, this event carries a high risk of stroke; after carotid endarterectomy, which has a low operative risk, there is a very low postoperative stroke rate.
However, the rate of subsequent stroke after amaurosis is significantly lower than after a transient ischemic hemispheric accident, therefore, there remains a debate as to the precise indications for which a carotid endarterectomy should be performed.
If the complete diagnostic study is completely normal, observation of the patient is recommended.
Approach to Transient Visual Loss
Nine young adults (19.5 years old) who suffered from Amaurosis Fugaz are described. The attacks were short in duration and preceded by premonitory symptoms in five cases and a migraine headache in two.
In five patients, visual loss progressed in a lacunar pattern unlike the “curtain” pattern characteristic of Amaurosis Fugaz in elderly patients. The investigation did not reveal evidence of an embolic or atheromatous etiology.
In two cases, a minor anomaly was found on echocardiography.
It was concluded that Amaurosis Fugaz in young adults has a different clinical pattern and may have a different etiology, possibly migraine, compared with that observed in elderly patients.
The pattern of visual loss in some of the cases suggests that the choroidal circulation rather than the retinal circulation is mainly affected.
By definition, patients with Amaurosis Fugaz almost always show up after the episode has resolved; therefore, the neurological and ophthalmological examination is usually normal.
Physicians rely on confidence in the patient’s description of the nature of visual symptoms and associated characteristics.
The relevant medical and family history can also provide valuable clues about the underlying diagnosis. Few case series of patients with Amaurosis Fugaz are reported.