Central Retinal Artery Occlusion

Sudden, complete, and painless loss of vision in one eye is characteristic of CRAO. The retina becomes opaque and edematous, particularly in the posterior pole, where the nerve fiber and ganglion cell layers are thickest (Fig 6-18). The orange reflex from the intact choroidal vasculature beneath the foveola thus stands out in contrast to the surrounding opaque neural retina, producing a cherry-red spot. Even prior to the appearance of the cherry-red spot, OCT imaging reveals a normal macular profile with diffuse hyperreflectivity and loss of internal layer definition (Activity 6-2; Fig 6-19). A cilioretinal artery may preserve some degree of macular vision if the area of retina perfused by it includes a sufficient portion of the maculopapillary bundle as well as the perifovea (see Chapter 1, Fig 1-8).

Courtesy of Colin A. McCannel, MD.

With time, the central retinal artery reopens or recanalizes and the retinal edema clears; however, the effect on visual acuity is usually permanent because the inner retina has been infarcted. In one study, 66% of eyes had final visual acuity worse than 20/400, and 18% of eyes had 20/40 or better. Most cases of 20/40 or better visual acuity occur in the presence of a patent cilioretinal artery (see Fig 6-18; also see Chapter 1, Fig 1-8). Vaso-occlusive vision loss to the level of no light perception is usually caused by choroidal vascular insufficiency from partial or complete ophthalmic artery occlusion or occlusions of the ciliary arteries in conjunction with occlusion of the central retinal artery (Fig 6-20). Studies in nonhuman primates have suggested that irreversible damage to the sensory retina occurs after 90 minutes of complete CRAO. Nevertheless, clinical return of vision can occur in some instances even if the obstruction has persisted for many hours.

Figure 6-18 Central retinal artery occlusion (CRAO). A, Fundus photograph shows superficial macular opacification and a cherry-red spot in the foveola. B, Angiography image reveals preservation of a sector of superonasal macula related to cilioretinal vessels, perfused in this image. The patient had hand motions visual acuity.

(Courtesy of Hermann D. Schubert, MD.)

Figure 6-19 SD-OCT scan of a case of CRAO similar to the one shown in Figure 6-18 with cilioretinal artery sparing shows hyperreflectivity in the area of clinical opacification of the inner two-thirds of the retina in the affected areas (X). All retinal layers are identifiable in the area of retina perfused by the cilioretinal artery, adjacent to the optic nerve head. The retina in the fovea is spared from opacification, resulting in the appearance of a cherry-red spot on examination. Subfoveal fluid (asterisk) is variably present in these cases.

(Courtesy of Colin A. McCannel, MD.)

CRAO is most often caused by embolization or atherosclerosis-related thrombosis occurring at the level of the lamina cribrosa. Less common causes are hemorrhage under an atherosclerotic plaque, thrombosis, trauma, spasm, and a dissecting aneurysm within the central retinal artery.

Emboli within the carotid distribution may cause transient ischemic attacks, amaurosis fugax, or both. Bright cholesterol emboli, or Hollenhorst plaques, typically located at retinal arterial bifurcations, suggest a carotid atheromatous origin and may be an indication for endarterectomy if accompanied by relevant symptoms and findings. Systemic etiologic considerations, such as those listed earlier in this chapter for BRAO, are important and require evaluation. The leading cause of death in patients with retinal arterial obstruction is cardiovascular disease with an elevated risk of myocardial infarction within the first 7 days following onset of the obstruction. Immediate referral for brain imaging in a stroke center is indicated, along with evaluation of the carotid arteries via Doppler ultrasound or computed tomography angiography (CTA) and of the cardiac valves via transesophageal echocardiography. Callizo studies have reported that as many as 78% of patients may have undiagnosed risk factors.

Figure 6-20 Central retinal and parent short ciliary artery occlusion. A, Fundus photograph of acute central retinal and short ciliary artery obstruction. Severe retinal opacification is present. The patient’s visual acuity was no light perception. B, Fluorescein angiography image taken 3 minutes after injection reveals hypofluorescence of the retinal vessels, the nasal choroid, and the optic nerve head, corresponding to an occlusion of the central retinal artery and nasal parent ciliary artery. The latter results in ischemia in the distribution of the short posterior ciliary arteries with a vertical watershed of choroidal perfusion.

(Courtesy of Hermann D. Schubert, MD.)

GCA accounts for approximately 1%–2% of CRAO cases. In cases of CRAO in which emboli are not readily visible, a thorough evaluation for GCA should be considered. The risk of GCA increases with increasing age. The erythrocyte sedimentation rate (ESR), C-reactive protein level, and fibrinogen levels—markers of inflammation—are usually elevated and can be checked. A complete blood count may detect an elevated platelet count, which is also suggestive of GCA; the blood count also aids in the interpretation of the ESR. If GCA is suspected as a cause, systemic corticosteroid therapy should be instituted promptly because the second eye can become involved by ischemia within hours to days after the first. In addition, a temporal artery biopsy should be performed shortly thereafter to confirm the diagnosis and justify the need for prolonged corticosteroid treatment. See BCSC Section 5, Neuro-Ophthalmology, for further discussion of GCA.

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