Amaurosis Fugax (Transient Vision Loss)
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Disease Entity
Amaurosis Fugax (transient vision loss)
Description
Amaurosis fugax (AF) refers to transient vision loss (TVL). AF can either be monocular (TMVL) or binocular (TBVL). It most commonly occurs monocularly, secondary to ischemia in the retina, choroid, or optic nerve. The most common cause of TMVL is an ipsilateral carotid artery disease (e.g., internal carotid artery dissection or atherosclerosis) with secondary thromboemboli[1], but it can also be a symptom of vasculitis (e.g., giant cell arteritis). AF can be a harbringer of impending stroke and thus merits urgent evaluation. TBVL is less common than TMVL and may be due to cortical lesions (e.g. migraine, seizure, or vertebrobasilar ischemia).[2] AF caused by ischemia is considered a form of transient ischemic attack (TIA) and usually lasts from seconds to minutes, followed by full visual recovery.[1] AF should be differentiated from structural optic disc and intraocular causes of TMVL (e.g., impending central retinal vein occlusion, optic disc drusen, or papilledema).
Etiology
Causes of TMVL can be divided into vascular (e.g. carotid pathology, cardioembolic source, GCA, vasospasm), neurologic (e.g. retinal migraine), or ophthalmic (e.g. papilledema, optic disc drusen, intermittent angle-closure glaucoma).[2] Causes of TBVL can be divided into the same categories. Vascular (e.g. TIA, bilateral carotid pathology and cardiac myxoma), neurologic (e.g., migraine, occipital seizure, posterior reversible encephalopathy syndrome), or ophthalmic (e.g. papilledema) etiologies must be considered.[2] Cardiac myxomas can cause transient vision loss, bilateral visual phenomena or acute blindness due to central retinal artery occlusion (CRAO) and other embolic events causing visual loss. [3]
Risk Factors
Risk factors for AF depend on the etiology, but for classic ischemic TMVL, the most important risk factor is carotid artery stenosis. Other risk factors include atrial fibrillation, hypertension, diabetes, hyperlipidemia, hypercoagulable state, and myeloproliferative disorders.[4] Cardiac myxomas are also a potential cause, with systemic symptoms including lightheadedness, limb claudication, and other systemic manifestations. [5]
Pathophysiology
TMVL can be caused by a number of etiologies as described above, but the common unifying mechanism is hypoperfusion of the retina or optic nerve. This hypoperfusion could be due to hypotension, thrombus, embolus, arteritis, or vasospasm. Most commonly, an embolus from the carotid artery breaks free and transiently occludes the central or branch retinal arteries or the ophthalmic artery. Rarely, but the emboli can originate from cardiac myxoma, which can dislodge and blockage anywhere including the aorta retinal arteries depending on the size of the tumor. [3] These cardiogenic embolic events can cause permanent visual loss or even stroke/ death if not treated promptly. If the ischemia targets the optic nerve, it is usually due to decreased perfusion through one or more posterior ciliary arteries.[4] TBVL can also occur due to the same hypoperfusion mechanism if it is bilateral (e.g., vertebrobasilar ischemia), as well as secondary to the other neurologic or ophthalmic etiologies described above. It also implies that the lesion is either bilateral anteriorly, chiasmal, or retrochiasmal.[2]
Diagnosis
History
An accurate history is important as it will heavily guide the differential diagnosis for AF. The age of the patient and the past medical history (e.g., vasculopathic risk factors, cardiogenic risk factors, history of migraines, cardiac or valvular disease, vasculitis) are important predisposing considerations. The patient should be asked whether the visual loss was unilateral or bilateral (e.g. visual loss with one or the other eye covered during the episode). Other features of the event including any triggering or precipitating factor, the duration of the episode, whether the resolution was complete vs. incomplete, and any symptoms that lingered afterwards all contribute heavily to the clinical picture.[2] Special concern should also be taken to inquire for any prior symptoms of GCA in elderly patients (e.g., jaw claudication, headache, scalp tenderness)
Physical examination
A complete ophthalmologic exam is mandatory (e.g., Hollenhorst plaque, angle closure glaucoma). Additionally, special attention should be given to the temporal artery region, examining for tenderness or erosions. A complete cardiovascular exam may also be performed with an emphasis on the presence of arrhythmias or a carotid bruit. Most patients with AF, however, have normal eye exams.
Symptoms
Patients usually report negative visual symptoms, typically lasting from seconds to minutes; however, longer episodes have been reported, and positive visual symptoms (though more rare) do not rule out an ischemic etiology.[4] Transient visual loss precipitated by gaze (i.e., gaze evoked AF) may suggest an orbital lesion.
Diagnostic workup
After ophthalmologic evaluation, laboratory tests include inflammatory markers like erythrocytes sedimentation rate (ESR) and C-reactive protein (CRP) to evaluate for GCA in elderly patients. Imaging of the carotid arteries and cardiac evaluation are generally recommended. Neuroimaging (e.g., magnetic resonance imaging (MRI) of the brain) and vascular imaging (e.g., CTA or MRA of head and neck) may show intracranial vascular occlusive disease, brain ischemia, or prior stroke. Electroencephalogram (EEG) may be indicated if the TVL was bilateral or if the history suggests a seizure.[6] Transthoracic echocardiography (TTE) and transesophageal echocardiography (TEE) are essential for identifying cardiac myxoma, and should be considered when accompanied symptoms suggest of cardiogenic source or in patient without clear predisposing vascular risk factor and unable to identify source of emboli. [5]
Management
Management of TMVL or TBVL depends on suspected etiology, but pertinently, if TIA is suspected, the patient should undergo an expedited stroke work-up. If GCA is suspected then the patient could be started on empiric steroid therapy, have laboratory testing (e.g., ESR and CRP) and undergo a temporal artery biopsy. Antiplatelet (e.g., aspirin) or anticoagulation (e.g., for atrial fibrillation) may be indicated depending on etiology. Surgery might be needed in case of atrial myxoma. [7]
Prognosis
The prognosis for amaurosis fugax varies depending on the underlying cause and the effectiveness of treatment. For cardiac myxomas, surgical removal generally offers a favorable prognosis, though long-term monitoring is essential. [7]
Complications:
Potential complications of untreated amaurosis fugax include:
Embolization and Obstruction: These can lead to stroke, limb ischemia, and other organ infarcts. [8]
References
- ↑ 1.0 1.1 Kvickström P, Lindblom B, Bergström G, Zetterberg M. Amaurosis fugax: risk factors and prevalence of significant carotid stenosis. Clin Ophthalmol [Internet]. 2016 Oct [cited 2019 Jul 7];Volume 10:2165–70. Available from: http://www.ncbi.nlm.nih.gov/pubmed/27826182
- ↑ 2.0 2.1 2.2 2.3 2.4 Thurtell MJ, Rucker JC. Transient Visual Loss. Int Ophthalmol Clin [Internet]. 2009 [cited 2019 Jul 7];49(3):147–66. Available from: https://insights.ovid.com/crossref?an=00004397-200904930-00012
- ↑ 3.0 3.1 Anderson JD, Lubow M. Atrial myxoma as a source of retinal embolization. Am J Ophthalmol. 1973;76(5):769-772.
- ↑ 4.0 4.1 4.2 Vodopivec I, Cestari DM, Rizzo JF. Management of Transient Monocular Vision Loss and Retinal Artery Occlusions. Semin Ophthalmol [Internet]. 2017 Jan 2 [cited 2019 Jul 7];32(1):125–33. Available from: http://www.ncbi.nlm.nih.gov/pubmed/27780399
- ↑ 5.0 5.1 Griborio-Guzman AG, Aseyev OI, Shah H, Sadreddini M. Cardiac myxomas: clinical presentation, diagnosis and management. Heart. 2022;108(11):827-833.
- ↑ Syndee Givre, MD, PhD, Gregory P Van Stavern, MD, ed. UpToDate. Waltham, MA: UpToDate Inc. https://www.uptodate.com/contents/amaurosis-fugax-transient-monocular-or-binocular-visual-loss/print?search=amaurosis-fugax&source=search_result&selectedTitle=1~42&usage_type=default&display_rank=1 (Accessed on July 8, 2019.)
- ↑ 7.0 7.1 Shah IK, Dearani JA, Daly RC, Suri RM, Park SJ, Joyce LD, Li Z, Schaff HV. Cardiac myxomas: A 50-year experience with resection and analysis of risk factors for recurrence. Ann Thorac Surg. 2015;100(2):495-500.
- ↑ Liu Y, Wang J, Guo L, Ping L. Risk factors of embolism for the cardiac myxoma patients: a systematic review and metanalysis. BMC Cardiovasc Disord. 2020;20(1):348. doi:10.1186/s12872-020-01631-w.
