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Show ! oumal or Clllllcal NellT( l-{ J/' hrllal",<' hJgy 9( 3): 185- 189. 1989. Amaurosis Fugax An Overview Ronald M. Burde, M. D. Amaurosis fugax is an all- inclusive term for all forms of transient visual loss. Clinically, it can be divided into four identifiable symptom complexes, each with its underlying pathoetiology: embolic, hypoperfusion, angiospasm, and unknown. Key Words: Amaurosis fugax- Classification- Carotid occlusive disease-- Atheromatous disease. From the Department of Ophthalmology. Albert Einstein College of Medicine, Montefjore Medical Center. Bronx, New York. Address correspondence and reprint requests to Dr. R. M. Burde, AECOM/ University Hospitals, 111 East 210 Street, Bronx, NY 10467, USA. 185 ":' 191\ 9 Raven Press. Ltd., New York " Amaurosis fugax" literally means " fleeting blindness" ( 1). Amaurosis fugax is the rubric commonly used to denote all bouts of transient visual loss, with the exception of those fleeting episodes measured in seconds associated with papilledema and raised intracranial pressure. These latter, short- lived attacks are termed " transient obscurations of vision," though they most closely fit the definition of amaurosis fugax. Burde et al. ( 2) proposed that the term amaurosis fugax should be reserved for discrete events with an abrupt onset. However, by accepted usage, amaurosis fugax herein will refer to any type of temporary visual loss with the exception of transient obscurations. This discussion will be based on Dr. Wray's classification with slight modification ( Table 1). CLASSIFICAnON Dr. Shirley Wray formalized a classification of amaurosis fugax based on the presumed underlying pathophysiology of the transient attacks ( 3). Her classification of amaurosis fugax is as follows: type I- transient retinal ischemia ( embolic); type II- retinal vascular insufficiency ( hypoperfusion); type III- angiospasm; and type IV- idiopathic. This classification is based on her personal experience in examining 850 cases of amaurosis fugax, seen between 1971 and 1987. Type I Amaurosis Fugax Type I amaurosis fugax is characterized by the abrupt loss of all or a portion of the vision in one eye, lasting seconds to minutes, with total recovery. The partial visual impairment may be described as a curtain, ascending, descending, or moving sideways, producing a uniocular attitudinal or hemianoptic defect ( 1). The patients may experience a central scotoma, paracentral scotoma, 186 Onset Visual loss Length Recovery Pain Pathophysiologic mechanism R. M. BURDE TABLE 1. Types of amaurosis fugax Type I Type II Type III Type IV Abrupt Less rapid Abrupt Abrupt All or partial All or partial Total or progressive Partial contraction of visual field Seconds to minutes Minutes to hours Usually minutes Seconds, minutes, or hours Complete Complete Complete usually Complete No Yes Often No Embolus to retinal Hypoperfusion due to Angiospasm of Unknown vessel carotid artery ophthalmic artery or occlusion central retinal artery or an area of segmental visual loss ( 4). In addition, patients may complain of vertical or horizontal stationary scintillating scotomas, which may be associated with ( a) vague, irregular background shadows that rapidly move to the periphery, and ( b) vague, irregular shadows suddenly appearing paracentrally and moving toward the periphery in seconds. Intensely bright, tiny scintillating lights suddenly appear paracentrally and move peripherally ( seconds) in a straight horizontal line, leaving behind a faint glowing line for 2 or 3 s ( 5). Most commonly, the visual loss is complete, the patient stating that everything is " completely black." Vision recovers in seconds to minutes, with recovery taking longer than loss. Variants include graying, dimming, or blurring of vision ( 4). The pathophysiologic mechanism is thought to be arterial occlusion due to emboli to the ophthalmic artery or to the retinal artery. In 1952, Fisher ( 6) noted the association of transient visual loss with contralateral hemiplegia. In 1959 ( 7), he observed the retina of a patient during a transient attack of monocular blindness and saw the passage of white bodies through the retinal arteries. These bodies, postulated to be emboli, impacted at arterial bifurcations, fragmented, and moved on, their disappearance coinciding with visual recovery. Subsequent reports by Russell ( 8), and McBrian and associates ( 9) characterized the white plugs as platelet thrombi. Hollenhorst ( 10) reported that 27 of 235 patients with carotid occlusive disease and 4 of 93 patients with vertebrobasilar disease " had from a single plaque to several dozen bright plaques that were orange, yellow, or copper in color and situated at various bifurcations of some of the retinal arterioles." In 1963, David et al. ( 11) demonstrated that these crystals consisted of cholesterol esters, whereas the intraarterial debris was made up of various fats as well. Types of emboli and presumed sources are listed in Table 2. The natural history of patients with this type of amaurosis fugax, as well as that for other types, is unknown, as a prospective study dividing the patients by embolic source has not been done. TABLE 2. Sources of emboli Type Patient age Cardiac Valves Rheumatic disease Lupus Acute or subacute endocarditis Floppy mitral valve Chamber Myxoma Mural thrombus Carotid artery Ulcerated plaque Stenosis Fibromuscular dysplasia Other Amniotic fluid Long bone fracture Chronic i. v. drug users Disseminated intravascular coagulapathy" Lupus anticoagulant" Platelet/ calcium" Platelet Marasmic Platelet Myxoma Platelet/ clot Platelet/ cholesterol ester Platelet Platelet Debris?" Fat" Talc · ?? ?? Any age Young women Damaged heart Any age; mostly women Older adult Older adult Young women Young women Any age Any age ?? ?? .- · '",: II0SIS flJgax [ see Russell ( 12) 1. I Clin Neuro- ophthalmol, Vol. 9, No. 3, 1989 AMAUROSIS FUGAX 187 Type II Amaurosis Fugax Type II amaurosis fugax is characterized by a less rapid onset of visual loss. In generaL it is of longer duration, lasting minutes to hours ( temporary rather than transient). Many of these patients complain of peculiar visual aberrations ( 2,13), such as loss of or excessive contrast vision, dazzle, photographic negative imagery, flickering lights, photopsias, and dyschromatopsias. In addition, patients experience a blurring or total loss of vision when they go out into ( or come in from) bright light, or upon assuming a sitting or upright position ( 13- 15). The visual loss is often described as a concentric contraction of the visual field " iris diaphragm effect," especially when bilateral. Rarely, a patient will report blindness after eating ( 16). Often, while reading, the patient will complain that the page becomes excessively bright. The patients also complain of chronic ocular or retrobulbar pain of an insidious and aching nature. All of these patients have severe carotid stenosis, either ipsilaterally or bilaterally, marked by low perfusion pressures on ophthalmodynamometric testing. The underlying pathophysiology of the visual experiences is retinal vascular insufficiency secondary to hypoperfusion. Many of these patients [ estimated to be 5% with severe internal carotid artery disease ( 17,18)] develop a compensatory retinopathy, termed " venous stasis retinopathy" by Kearns and Hollenhorst ( 17). The retinopathy is progressive, going through a series of evolutionary stages that reflect progressive ischemia. The endresult is global ischemia of the eye with rubeosis iridis and glaucoma. The ocular signs of venous stasis retinopathy ( Table 3) and carotid insufficiency ( Table 4) are listed. The causes of type II amaurosis fugax are listed in Table 5; the most common cause is carotid occlusive disease. Type II amaurosis fugax may be mimicked by TABLE 3. Ocular signs of venous statis retinopathy { 5% of patients with ipsilateral carotid occlusive disease ( 17)] Early signs Microaneurysms: small dot and blot Intraretinal hemorrhages. nerve fiber layer hemorrhages: most prominent within vascular arcades extending to midperiphery With more severe ischemia Dilation and darkening of retinal veins Mild swelling of optic disc Retinal clouding End- stage Ocular ischemic syndrome ( see Table 4) TABLE 4. Ocular signs of carotid insufficiency Dilated episcleral arteries ( 19) Venous stasis retinopathy ( 17.20) Ocular ischemic syndrome ( 21- 23) Conjunctival hyperemia Corneal edema Cells and flare in anterior chamber Segmental ischemia of the iris ( 24) Rubeosis iridis [ 12% of cases ( 24) 1 Glaucoma/ hypotony Cataract Anterior ischemic optic neuropathy Central retinal artery occlusion Pulsating central retinal artery recurrent spontaneous anterior chamber hemorrhages, the causes of which are legion ( 26). These attacks may often cause visual dysfunction for hours and may be accompanied early on by the peculiar complaint of erythropsia. Type III Amaurosis Fugax Type III amaurosis fugax is characterized by the sudden onset of total visual loss or progressive contraction of the visual field sparing fixation ( 27). These attacks are usually short- lived in terms of minutes ( 27,28), but may be prolonged ( 29). Direct observations of the fundus during such attacks have revealed ( a) narrowing of the retinal arteries and veins, cessation of blood flow, segmentation of the blood columns, and optic disc pallor, and ( b) narrowing of the retinal veins. Fluorescein angiography reveals early filling of the optic disc capillaries with late filling ( 30 s) of the retinal arterioles in the former case ( a), and a delay in filling the central retinal artery in the latter ( b). Many of these patients have a known migraine diathesis. The underlying pathophysiologic mechanism is that of angiospasm. Patients have been reported with spasm of the ophthalmic artery ( 30) as well as the central retinal artery. It is postulated that the vast majority of these patients are experiencing a migraine equivalent. A number of cases, now clas- TABLE 5. Cause of Type / I amaurosis fugax, venous statis retinopathy, and occular ischemic syndrome Carotid occlusive disease Systemic arterides Giant cell arteritis Pulseless disease Polyarteritis nodosa Aortic arch syndrome Increased blood viscosity Polycythemia Leukemia Dysproteinemia Direct carotid cavernous fistula ( 25) I Clin Neuro- ophlhalmol, Vol. 9, No. 3, 1989 188 R. M. BURDE sified as " type IV amaurous fugax" or idopathic transient visual loss, probably fall into this migraine equivalent category as well. Type IV Amaurosis Fugax Type IV amaurosis fugax is a " wastebasket" category in which the signs and symptoms defy classification. The type of visual disturbance in this group of patients closely resembles type I, except for the duration of the attack, which may be very short ( like a transient obscuration of vision) or very long ( thus resembling a type III attack). In general, the patients suffer from multiple attacks, some occurring as frequently as one or two times per day. No identifiable pathophysiologic mechanism can be determined ( Table 6). In Wray's series ( 3), roughly 25% of cases fell into this category, with about 11% of these patients being under 30 years of age. The experience at Washington University parallels that reported by Dr. Wray, in that this is a benign process, and these patients have an excellent prognosis ( 31). DIAGNOSIS The approach to a patient presenting with monocular transient visual loss follows the classic format of a detailed historical inquiry, followed by an appropriate physical examination. An age- related differential diagnosis is important in the absence of historical signs and symptoms of systemic disease. As mentioned previously, a meaningful natural history of amaurosis fugax is not available, as no one has examined the problem from a pathologic! etiologic perspective. All patients presenting with amaurosis fugax should have a cardiac source of embolism excluded. TREATMENT This article is confined to both carotid occlusive and atheromatous disease. Hurwitz et al. ( 32) have demonstrated that although patients with amaurosis fugax and transient ischemic attacks are at an increased risk to develop stroke, the latter group is at a much greater risk. At 7 years after the onset of symptoms, 27cf" of their patients with TABLE 6. Type IV amaurosis fugax Idiopathic associations? Myopia OrtY':, I_':: I Clin Neuro- ophthalmol, Vol. 9, No. 3, 1989 transient ischemic attacks, compared to 14% of patients with isolated amaurosis fugax, suffered a stroke. If an embolic source from the carotid circulation is suspected, platelet antiaggregant therapy is indicated ( 325 mg aspirin p. o. daily). As regards surgical intervention for amaurosis in isolation ( 33), the vascular surgical team must have a perioperative mortality and morbidity rate of less than 2.9% to justify this procedure. Although both carotid endarterectomy ( 22,34) and external carotidinternal carotid bypass have been reported to ameliorate the ocular ischemic syndrome in a small number of cases, it seems prudent to consider antiaggregant therapy, as well as stellate ganglion block, prior to surgical intervention. Acknowledgment: This investigation was supported in part by an unrestricted grant from Research to Prevent Blindness in New York. REFERENCES 1. Sandok BA, Trautmann JC, Ramirez- Lassepas, et al. CIinical- angiographic correlations in amaurosis fugax. Am JOphIIwlmol 1974; 79: 137. 2. Burde RM, Savino PJ, Trobe JD. Clinical decisions in neuroophthalmology. 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