Journal of Neuro-Ophthalmology, September 1989, Volume 9, Issue 3

The significance of retinal emboli.

This review contrasts two of the more common forms of retinal emboli, i.e., cholesterol emboli and calcific emboli. These two forms vary in ophthalmoscopic appearance and in regard to significance.

Journal of C1l1llcal Neuro- ophlhalmolo, y 9( 3): 190-- 194, 1989. The Significance of Retinal Emboli Brian R. Younge, M. D. © 1989 Raven Press, Ltd., New York This review contrasts two of the more common forms of retinal emboli, i. e" cholesterol emboli and calcific em­boli, These two forms vary in ophthalmoscopic appear­ance and in regard to significance, Key Words: Cholesterol emboli- Calcific emboli, From the Department of Ophthalmology, Mayo Clinic and Mayo Foundatiun, Rocht'ster, Minnesota Addn'ss corn',!'<) nd" nce ,1nd rl'Print requests to Dr. B. R. ': '",,: d '( I"'! " W, Rocht'ster, MN 190 Retinal embolization indicates the presence of significant vascular disease and the potential for severe tissue damage. Such embolization may be apparent to the patient in the form of visual symp­toms or may be noticed by the physician as a sign while performing a routine ophthalmoscopic ex­amination. Probably the most common form of embolus is the cholesterol embolus or Hollenhorst plaque ( 1). This suggests atheromatous disease in the proxi­mal carotid artery, and it may also be an important warning sign of an impending stroke or coronary artery occlusion. Other types of embolization are less common, but are nonetheless important as far as their etiology is concerned. Table 1 illustrates the most common forms of embolization seen in retinal vessels. The calcific embolus is most likely to be found in the first- or second- order bifurca­tion. The calcific embolus has a high probability of producing a retinal infarction and corresponding visual loss. Mycotic emboli do not usually produce significant loss of vision, but are important signs of systemic bacterial or fungal endarteritis. Some­times coupled with flame hemorrhages, small ret­inal white infarcts ( Roth spots) can occur in pa­tients with subacute bacterial endocarditis or other septic vascular conditions. In drug abusers who intravenously inject " pulverized" tablets of nar­cotic drugs or impure " cut" substances, the injec­tion talc may be apparent as small white opacities in retinal terminal twigs around the maculae. A rarer form of embolus is that from artificial heart valve implants, such as Teflon particles, bits of ny­lon, or synthetic materials from disintegrating valves and sutures. CONTRAST OF CHOLESTEROL EMBOLI VERSUS CALCIFIC EMBOLI The two most common types of retinal emboli are the cholesterol embolus and the calcific embo­lus. These will be contrasted. RETINAL EMBOLI 191 TABLE 1. Retinal emboli Ophthalmoscopic Appearance Cholesterol embolus Hollenhorst first drew attention to bright orange plaques in the retinal vasculature as being of an embolic origin ( 1); further studies by David and coworkers ( 2) and Hollenhorst et a1. ( 3) confirmed the cholesterol nature of these plaques. Choles­terol emboli are little plates of thin crystals that are bright and shiny in appearance. They lodge, for the most part, in bifurcations of arteries or smaller arterioles ( Fig. 1), and as such, do not occlude any but the most tiny of twigs. However, cholesterol emboli, when in association with fibrin and plate­let, form clumps that may cause an occlusion with or without associated retinal infarction. The orien­tation of these cholesterol plaques may be such that they are not immediately visible on ophthal­moscopy; sometimes light pressure on the eye, ei­ther digitally or with the ophthalmodynameter, will bring out the flashing of golden- orange plaques simultaneously with the pressure- induced Endogenous Cholesterol Fibrin/ platelet Calcific Mycotic Fat Thrombotic ( atrial myoma) Exogenous Talc granules Air Teflon Nylon Mercury Depo Medrol Zyderm Parafin Penicillin arterial pulsations. The author and his colleagues have on occasion seen streams of fibrin/ platelet and cholesterol emboli coursing along retinal ves­sels in patients actually experiencing amaurosis fugax at that moment. Temporary occlusion of the central retinal artery that is of sufficient duration to produce irreversible visual loss can occur because of combined fi­brin/ platelet and cholesterol embolization in the immediate retrobulbar region; quite frequently, within the next few days, the retinal artery is once again patent with normal retinal arterial pressures. This indicates resolution of the embolic obstruc­tion. Despite patency of the vessel, sometimes there may remain an atheromatous sheath at the previous site of occlusion, either on the disc or at a more distal bifurcation. Calcific emboli Calcific emboli, on the other hand, are very dif­ferent in appearance. They are more solid in shape, dirty yellowish- white in color, and do not flash with pressure- induced arterial pulsations. They tend to lodge in the first- or second- order arteries ( Fig. 2) and often overlie the optic disc it­self, where the color tends to be camouflaged by the similar background ( Fig. 3). Given its chunky character, the calcium embolus is most likely to partially or totally occlude the vessel distally and usually remains there forever after. In contrast, the cholesterol embolus usually disappears within a few days or weeks. FIG. 1. Cholesterol embolus lodged in an arterial bi­furcation. superior temporally, in the left eye. Photo­graph courtesy of Dr. Ronald Burde. FIG. 2. Calcific embolus lodged in arteriole, inferior temporally, just below optic disc of the right eye, with distal vascular occlusion. Note the thready arteriole. JClin Neuro- ophthalmol. Vol. 9, No. 3, 1989 192 B. R. YOUNGE FIG. 3. Central retinal arterial occlusion with calcium embolus lodged on the disc surface and camouflaged by the background color of the optic disc. Etiology Cholesterol embolus As indicated previously, the source of a choles­terol embolus is usually atheromatous disease in the proximal carotid artery. Calcific embolus The source is usually aortic valve disease, but they may also arise from the aorta or the carotid artery. Some studies have documented occurrence in rheumatic heart disease and during valvotomies on calcified aortic valves or valve replacements ( 4). Arruga and Sanders ( 5) described 70 patients with retinal artery emboli; four of the six with calcific emboli had calcific vegetation of the aortic valve. Signs and Symptoms In both types of embolus, there is a loss of vi­sion. However, the visual effects in the cho­lesterol/ fibrin/ platelet type of embolus are more fleeting, i. e., amaurosis fugax. By contrast, the lodging of a calcific embolus is more likely to pro­duce a sudden and permanent loss of vision, either total or sector. Accompanying symptoms of tran­sient ischemic attacks or strokes occur only with the cholesteroVfibrin/ platelet type of embolization. Transient ischemic attacks are not a feature of cal­cific emboli, unless a large number of such emboli are released at the time of surgery on the aortic or mitral valves. With either type of embolization, there m, l'! not be any wmptoms, either ocular or · . d,-,, · occlusion occurs. I elm Nt'llw- ophlhulmuJ, Vol ': l . . ,"' J, ll,_' Diagnosis Cholesterol embolus- symptomatic In the case of a patient who has transient isch­emic attacks, with the finding of arterial choles­terol emboli, the investigation is fairly straight for­ward. This includes an evaluation of the carotid flow by various noninvasive and invasive tech­niques ( 6). Cholesterol embolus~ symptomatic The patient with the isolated asymptomatic cho­lesterol embolus and no history of coronary artery disease or stroke causes concern on the part of the examiner. Knowing that this patient may be at risk is sufficient, in the author's estimation, to warrant at least a thorough general physical with emphasis on the cardiovascular and neurovascular areas. Currently, at the Mayo Clinic, the recommended studies include oculopneumplethysmography, ca­rotid ultrasonography, Doppler examination, and blood studies to search for other risk factors. Be­yond that, depending on the individual patient, a digital subtraction angiogram might be indicated. However, only if the patient appears to be a sur­gical candidate, does the author advise angiogra­phy. Calcific embolus In those patients with calcific emboli, whether or not there is visual loss, the investigation is directed more toward the heart valves, i. e., the mitral and aortic valves. Figure 4A is a photo of a normal mitral valve, and Fig. 4B is a photo of a normal aortic valve. By contrast, Fig. 4C is a photo of a diseased mitral valve, and Fig. 4D is a photo of a diseased aortic valve. Two- dimensional echo stud­ies may reveal thickened, calcified valve leaflets or a tight calcified annulus ( Fig. SA and B). Such find­ings are suggestive of the source of calcific emboli. Significance Cholesterol embolus Pfaffenbach and Hollenhorst ( 7) summarized the experience of the Mayo Clinic in a series of patients of Hollenhorst's, each patient having had choles­terol ( or other forms of emboli) in the retina. Since then, several studies have been performed to as­certain the significance of emboli ( 5). At the time of observation, 93% of the patients in the series by Pfaffenbach and Hollenhorst ( 7) had already had RETINAL EMBOLI 193 FIG. 4. Heart valves. Normal mitral ( A) and aortic valves ( 8). ( C) Mitral valve with calcification and thickened chordal tendineae. ( D) Degenerated aortic valve with cal­cific deposits. some clinical signs of arteriosclerotic vascular dis­ease. In a 6- 15- year follow- up of these patients, some 65% of them were dead, mostly of carotid disease or stroke. Given the possible inadvertent preselection of patients in the referral system of the Mayo Clinic, a further study is being undertaken to ascertain the significance of cholesterol emboli in a population­based study of Olmsted County. There is an on­going controversy over the numbers of carotid endarterectomies being done in the United States and the indications for such surgery. Thus, it is important to be certain as to prognosis for life in patients who have cholesterol emboli. Calcific embolus By contrast, a preliminary study by Minton et a1. ( manuscript in preparation) of 72 patients with cal­cific emboli indicates the survival rate to be close to that of the normal population. Compared to the patients with cholesterol emboli followed by Pfaf­fenbach and Hollenhorst, it will be noted that the prognosis for survival is much less in patients with calcific emboli ( Fig. 6). Management Cholesterol embolus A cholesterol embolus is indicative of atheroma­tous disease of the carotid artery. Also, it may be indicative of more widespread dissemination of atherosclerosis with risk of embolism. The best management of high- grade carotid artery stenotic disease is clearly surgical if the perioperative com­plication rate is less than 2%. This entails assess­ment of the vascular status, not only of the carotid system, but also of at least the cardiac vessels and the major peripheral arterial system. At the Mayo Clinic, the perioperative mortality rate in carotid endarterectomies is less than 0.5% and the complication rate is less than 2%, even with the inclusion of high- risk patients, such as those with concomitant coronary artery disease and cerebral vascular insufficiency. Anticoagulation with aspirin for carotid ulcer- I Clin Neuro- ophthalmol, Vol. 9, No. 3, 1989 194 B. R. YOUNGE FIG. 5. Two- dimensional echocardiograms. ( A) Longi­tudinal view of normal mitral and aortic valves. Ao, aorta; LA, left atrium; LV, left ventricle; mv, mitral valve; RV, right ventricle. ( 8) Longitudinal and trans­verse views of calcified mitral and aortic valves ( ar­rows) with thickened leaflets. ation without significant stenosis is a reasonable alternative and carries a lower rate of complication than does endarterectomy. However, if symptoms persist, surgical treatment may be advisable. It is r- J!""-, I'r., r, · , j , IJrJI'),' ll ; jl" ll' " rTIl") f', f, r''' IIIf- r'l' IJt,,:(-, I{'~' ""' Ial _______________ ~ I' , I, · , I, r' " ~ " II ' , " - I Years FIG. 6. Observed survivor curves for 208 patients with embolic cholesterol crystals in ocular fundus [ data from Pfaffenbach and Hoilenhorst ( 7)] and for 72 pa­tients with calcific emboli. Expected survival is for a Minnesota white population of the same age and sex distribution from the 1950 life table. [ Modified from Pfaffenbach and Hoilenhorst ( 7).] I CIl1z Ncuru- ophthalmol, V'u1 4, ill 1' I" , in this group of patients that the issue of best man­agement arises. Coumadin anticoagulation is an­other conservative alternative, but unfortunately, it carries some risk. Calcific embolus If the patient has sufficient symptoms, then valve surgery is warranted. However, more often than not, the patient with an isolated calcific em­bolus will merely be followed without treatment. It is most unusual to have subsequent retinal embo­lization from another calcific embolus ( the author has not seen such a case). Prognosis As prognosis is different depending on whether the embolus is cholesterol or calcific, it is important clinically to identify those patients who need at­tention. The author intends to report the study of patients with calcific emboli when sufficient fol­low- up data are available and to undertake a pop­ulation- based study of risk factors in patients with isolated cholesterol emboli. In the meantime, ex­aminers who diagnose cholesterol or other forms of emboli are advised to choose their investigating centers with care, in the hopes of obtaining the best type of examination, evaluation, and subse­quent therapy to minimize the risk to the patient by preventing impending disaster or complica­tions. REFERENCES 1. Hollenhorst RW. Significance of bright plaques in the reti­nal arterioles. lAMA 1961; 178: 23. 2. David NJ, Clintworth GK. Freedberg SJ, Dillon M. Fatal atheromatous cerebral embolism associated with bright plaques in the retinal arterioles: report of a case. Neurology 1963; 13: 708. 3. Hollenhorst RW, Lensink ER, Whisnant JP. Experimental embolization of the retinal arterioles. Trans Am Ophthalmol Soc 1962; 60: 316. 4. Penner R, Font RL. Retinal embolism from calcified vege­tation of aortic valve. Arch OphtlzalmoI1969; 81: 565. 5. Argua L Sanders MD. Ophthalmologic findings in 70 pa­tients with evidence of retinal embolism. Ophthalmology 1982; 89: 1336, 6. Becker WL, Burde RM. Special article: carotid artery dis­ease: a therapeutic enigma. Arch OphthalmoI1988; 106: 34. 7. Pfaffenbach DR, Hollenhorst RW. Morbidity and survivor­ship of patients with embolic cholesterol crystals in the oc­ular fundus. Am IOphthalmoI1973; 75: 66.