Retinal Artery Occlusions
Central retinal and branch retinal artery occlusions produce acute monocular visual loss. Unless the retinal vascular occlusion is secondary to giant cell arteritis or to a carotid dissection, the visual loss is painless.
Permanent visual loss may have been preceded by one or more episodes of transient monocular visual loss.
The visual prognosis is usually poor. These patients are at risk of recurrent ocular or cerebral infarction, and, like patients with cerebral infarctions, they should be evaluated emergently.
7.1.1 Types of Retinal Artery Occlusions
Asymptomatic Cholesterol Retinal Emboli
Asymptomatic retinal emboli (most often cholesterol) are found in 1 to 2% of patients older than age 50 (▶ Fig. 7.1). They should prompt an evaluation for atheromatous vascular risk factors, which need to be aggressively controlled.
Fig. 7.1 Asymptomatic cholesterol retinal emboli (arrows). The emboli are located at arterial bifurcations and are bright.
Central Retinal Artery Occlusion
Central retinal artery occlusion results in severe monocular visual loss (▶ Fig. 7.2, ▶ Fig. 7.3, ▶ Fig. 7.4). It is associated with retinal edema with a cherry red spot (the fovea appears red by contrast with the surrounding ischemic retina, which is whitish). The retina is very thin at the fovea, and the underlying normally vascularized choroid appears red. The retinal edema develops within a few hours, and the fundus may be almost normal initially. The retinal arteries are usually attenuated, sometimes with emboli. There is a dense relative afferent pupillary defect (RAPD) because the inner retinal layers, including the nerve fiber layer, are affected.
Fig. 7.2 Acute central retinal artery occlusion in the right eye (seen 24 hours after visual loss). The retina is diffusely pale and the fovea appears red (cherry red spot). The arteries are attenuated.
Fig. 7.3 Acute central retinal artery occlusion in the left eye, with a cherry red spot (arrow) (seen 3 hours after visual loss). There is a retinal hemorrhage above the macula, but the retina is not edematous yet, and therefore does not appear pale.
Fig. 7.4 Acute central retinal artery occlusion in the left eye, with multiple retinal emboli (seen at least 10 hours after visual loss). There are scattered retinal hemorrhages.
Approximately 30% of patients have a cilioretinal artery, which originates from the posterior ciliary circulation. In cases of central retinal artery occlusion, the retinal territory vascularized by the cilioretinal artery is not affected, and some vision is preserved (▶ Fig. 7.5). If the cilioretinal artery provides the blood supply to the fovea, then the central visual acuity remains good.
Fig. 7.5 Acute embolic central retinal artery occlusion with cilioretinal sparing in the right eye. The ischemic retina is whitish, whereas the retina is still normal in the territory of the cilioretinal artery.
Ophthalmic Artery Occlusion
Like central retinal artery occlusion, ophthalmic artery occlusion results in severe monocular visual loss and is associated with a dense RAPD; attenuated retinal arteries, sometimes with emboli; and retinal edema (▶ Fig. 7.6). Unlike central retinal artery occlusion, there is no cherry red spot (the underlying choroid is also ischemic). There is often associated mild disc edema from optic nerve ischemia.
Fig. 7.6 Acute ophthalmic artery occlusion in the left eye. The retina is diffusely pale, and there is no cherry red spot because the choroid is also ischemic. The arteries are very attenuated, and there are a few hemorrhages superiorly.
Ophthalmic artery occlusion is most often related to internal carotid artery disease, with large emboli involving the origin of the ophthalmic artery. Giant cell arteritis should also be considered.
Branch Retinal Artery Occlusion
Branch retinal artery occlusion is characterized by partial monocular visual loss, a moderate RAPD, an attenuated branch retinal artery, usually with one or more emboli, and localized retinal edema (▶ Fig. 7.7, ▶ Fig. 7.8, ▶ Fig. 7.9). There is a corresponding visual field defect (usually superior or inferior altitudinal). This type of occlusion is most often related to emboli in the branch retinal artery. The clinical features of the emboli sometimes allow understanding of the nature and the source of the emboli (▶ Table 7.1). Giant cell arteritis is less likely.
Fig. 7.7 Acute superior branch retinal artery occlusion in the left eye. Platelet fibrin emboli are seen in numerous arteries (yellow arrows). The ischemic retina is edematous and appears pale (white arrows).
Fig. 7.8 Selective catheter angiogram of the left common carotid artery showing a severe internal carotid artery stenosis (yellow arrow) in a patient with a branch retinal artery occlusion.
Fig. 7.9 Transesophageal echocardiogram showing a mass on the mitral valve (arrow) in a patient with recurrent episodes of transient monocular visual loss in both eyes, followed 2 weeks later by a central retinal artery occlusion in the right eye and a branch retinal artery occlusion in the left eye.
Retinal emboli | Funduscopic appearance | Source of emboli |
Cholesterol (Hollenhorst plaque) | Yellow, refractile emboli (multiple in 70% of cases); appear wider than the arteriole; often located at an arteriole bifurcation | Ipsilateral internal carotid artery or aortic arch atheroma |
Platelet—fibrin | White, gray emboli, pale, not refractile, often multiple; usually seen distally within the small retinal arterioles | Thrombus (carotid or aortic arch atheroma), cardiac thrombus, cardiac prosthesis |
Calcium | White, large emboli, usually isolated; located in the proximal segment of the central retinal artery or its branches | Calcified cardiac valve or calcified atheromatous plaque |
Talc | Multiple, yellow emboli; refractile | Intravenous drugs |
Fat | Multiple whitish spots, hemorrhages, cotton wool spots | Long bone fractures |
Neoplasm | White, gray emboli, often multiple | Cardiac myxoma |
Infectious | Multiple white spots (Roth spots) | Bacterial endocarditis, candidemia |
Susac syndrome is a very rare cause of recurrent branch retinal artery occlusions. It is a vasculopathy of unknown cause leading to occlusion of small retinal, cochlear, and cerebral arteries, mostly occurring in young women. It is characterized by the clinical triad of branch retinal artery occlusions, hearing loss, and encephalopathy with focal neurologic signs and psychiatric manifestations.
Recommended tests include ocular examination with retinal fluorescein angiography to look for occlusion of multiple arterial branches, either uni- or bilateral; an audiogram to determine whether hearing loss is uni- or bilateral; and magnetic resonance imaging (MRI) with gadolinium to check for multiple small enhancing lesions in the white and gray matter of the brain.
Giant Cell Arteritis
Retinal ischemia can be caused by giant cell arteritis (▶ Fig. 7.10). It is usually associated with optic nerve ischemia or choroidal ischemia (see Chapter ▶ 20).
Fig. 7.10 Acute central retinal artery occlusion and anterior ischemic optic neuropathy in the right eye of a 78-year-old woman in the setting of giant cell arteritis. Visual acuity is light perception only, and there is a dense right relative afferent pupillary defect. The arteries are attenuated, and there is a cherry red spot. There is also pallid disc edema (closer view on the right), suggesting associated anterior ischemic optic neuropathy.
Pearls
The association of branch or central retinal artery occlusion with anterior ischemic optic neuropathy is highly suggestive of giant cell arteritis.
7.1.2 Causes and Evaluation of Patients with Acute Retinal Arterial Ischemia
Giant cell arteritis, carotid disease, and other sources of emboli are classic causes of retinal ischemia (see ▶ Table 7.2).
Causes | Tests to obtain |
Giant cell arteritis | CBC, platelets, ESR, CRP Consider fluorescein angiogram Temporal artery biopsy if high suspicion |
Associated (silent) cerebral infarction | Brain MRI with diffusion-weighted images (DWI) or head CT |
Carotid disease (ipsilateral):
| Carotid ultrasound (with transcranial Doppler evaluating ophthalmic artery and intracranial circulation) or CT angiogram or MRA of head and neck |
Aortic arch atheroma | Transesophageal echocardiogram CT angiogram of the aortic arch or MRA of the aortic arch |
Cardiac source of emboli | Electrocardiogram ; cardiac monitoring Transthoracic ± transesophageal echocardiogram Holter monitoring if indicated |
Hypercoagulable disorder
| Blood tests looking for hypercoagulable states and causes of hyperviscosity, including thrombophilia, antiphospholipid antibody syndrome, hyperhomocysteinemia, sickle cell disease, monoclonal gammopathy, cancer, infection, and disseminated intravascular coagulation |
Abbreviations: CBC, complete blood count; CRP, C-reactive protein; CT, computed tomography; ESR, erythrocyte sedimentation rate; MRI, magnetic resonance imaging; MRA, magnetic resonance angiography. aThe causes of acute retinal artery occlusions and appropriate tests are organized from the most urgent or common to the least likely. | |
7.1.3 Treatment of Acute Retinal Arterial Ischemia
Acute treatment consists of the following:
Patients seen acutely should be admitted for immediate workup by a stroke neurologist and initiation of secondary prevention.
Most treatments used have not proven to be effective and are decided on a case-by-case basis.
Reduce the intraocular pressure (ocular massage, drops).
Consider thrombolytics for central retinal artery occlusion in selected patients seen within a few hours of visual loss.
In cases of giant cell arteritis, admit the patient for high-dose intravenous steroids (methylprednisolone 250 mg every 6 hours for 3 or 5 days) followed by oral prednisone (1 mg/kg/d).
Secondary prevention of ocular and cerebral infarction is characterized as follows:
Should be initiated at the time of diagnosis
Is similar to that recommended for patients with cerebral infarctions and transient visual loss (see Chapter ▶ 6)
7.2 Ocular Ischemic Syndrome
Chronic hypoperfusion of the eye results in diffuse ocular ischemia. Ocular ischemia develops in patients with severe stenosis or occlusion of the ipsilateral internal carotid artery and poor collateral circulation. These patients often have low blood flow in the ophthalmic artery. The flow is sometimes reversed in the ophthalmic artery to protect the ipsilateral brain (there is then a steal phenomenon involving the eye) (see Chapter ▶ 6, ▶ Fig. 6.15 and ▶ Fig. 6.16).
7.2.1 Features
Venous stasis retinopathy (▶ Fig. 7.11), or hypotensive retinopathy, is the first sign of chronic ocular ischemia. It resembles diabetic retinopathy or central retinal vein occlusion and is characterized by a unilateral appearance, dilation and tortuosity of the retinal veins, and blot hemorrhages, mostly in the midperiphery of the retina.
Fig. 7.11 Venous stasis retinopathy in a patient with internal carotid occlusion. The veins are dilated and tortuous. There are multiple large dot-blot hemorrhages in the midperiphery of the retina.
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