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Ophthalmology – Central and Branch Retinal Artery Occlusion (CRAO & BRAO)
Central and branch retinal artery occlusions are ophthalmic emergencies caused by interruption of blood flow to the inner retina. The central retinal artery supplies the inner retinal layers, and its occlusion (CRAO) results in profound ischemia, whereas occlusion of a branch retinal artery (BRAO) leads to localized retinal infarction. Both conditions typically present with sudden, painless, monocular vision loss, although the severity varies depending on the location and extent of the occlusion.
These conditions are strongly associated with systemic vascular risk factors such as hypertension, diabetes mellitus, carotid artery atherosclerosis, cardiac valvular disease, and hypercoagulable states. The underlying mechanism involves loss of retinal perfusion leading to ischemia and infarction. The most common cause is embolism, with different types of emboli including cholesterol (Hollenhorst plaques), platelet-fibrin, calcium, fat, septic emboli, and others. Additional causes include thrombosis, vasculitis such as giant cell arteritis, vasospasm, trauma, and systemic diseases like sickle cell anemia or autoimmune disorders.
Patients typically present with acute, painless vision loss in one eye. In CRAO, the vision loss is usually severe, often reduced to counting fingers or light perception. In contrast, BRAO may present with partial visual loss, scotomas, or even be asymptomatic if the macula is spared. Some patients report transient vision loss episodes (amaurosis fugax) prior to the event. In older patients, symptoms such as headache, jaw claudication, and scalp tenderness raise concern for giant cell arteritis, which requires urgent evaluation.
On examination, a relative afferent pupillary defect is commonly present, particularly in CRAO. Fundoscopic findings in CRAO include diffuse retinal whitening and edema in the posterior pole with the classic “cherry-red spot” at the fovea. This occurs because the fovea is supplied by the choroidal circulation and remains relatively spared. In BRAO, retinal whitening is localized to the distribution of the affected artery. Emboli may sometimes be visualized within retinal arterioles, and the blood column may appear segmented, known as “boxcarring,” indicating poor perfusion.
Diagnosis involves both ocular and systemic evaluation. Laboratory tests include complete blood count, inflammatory markers such as erythrocyte sedimentation rate and C-reactive protein, lipid profile, and blood glucose. Additional testing may be required to evaluate for hypercoagulable states or infectious causes. Imaging studies such as fluorescein angiography can demonstrate delayed arterial filling, while carotid ultrasound, echocardiography, and electrocardiography are important for identifying the source of emboli. If giant cell arteritis is suspected, urgent temporal artery biopsy is indicated.
Management options for CRAO and BRAO are limited and often yield poor visual outcomes, especially in CRAO. Immediate measures aim to restore retinal perfusion, although their effectiveness is uncertain. These include lowering intraocular pressure with medications such as topical agents or oral acetazolamide, ocular massage to dislodge emboli, and anterior chamber paracentesis. If giant cell arteritis is suspected, high-dose systemic corticosteroids must be initiated immediately to prevent involvement of the fellow eye. Antiplatelet therapy such as aspirin may also be considered.
Long-term management focuses on identifying and controlling systemic risk factors to prevent further vascular events. Patients should be referred for comprehensive cardiovascular evaluation. Follow-up is essential to monitor for complications, particularly neovascularization of the iris or retina, which can lead to neovascular glaucoma. This typically occurs several weeks after the initial event and may require treatment with panretinal photocoagulation or anti-VEGF therapy.
The prognosis differs between CRAO and BRAO. CRAO generally has a poor visual prognosis, with most patients experiencing permanent severe vision loss. In contrast, BRAO has a better outcome, and many patients recover visual acuity to 20/40 or better, especially if the macula is not involved. Complications include neovascular glaucoma, vitreous hemorrhage, and other sequelae of ocular neovascularization.
Early recognition of retinal artery occlusion is critical, not only for potential ocular intervention but also because it may signal underlying systemic vascular disease, including an increased risk of stroke. Prompt multidisciplinary evaluation and management are therefore essential.
Central and branch retinal artery occlusions are ophthalmic emergencies caused by interruption of blood flow to the inner retina. The central retinal artery supplies the inner retinal layers, and its occlusion (CRAO) results in profound ischemia, whereas occlusion of a branch retinal artery (BRAO) leads to localized retinal infarction. Both conditions typically present with sudden, painless, monocular vision loss, although the severity varies depending on the location and extent of the occlusion.
These conditions are strongly associated with systemic vascular risk factors such as hypertension, diabetes mellitus, carotid artery atherosclerosis, cardiac valvular disease, and hypercoagulable states. The underlying mechanism involves loss of retinal perfusion leading to ischemia and infarction. The most common cause is embolism, with different types of emboli including cholesterol (Hollenhorst plaques), platelet-fibrin, calcium, fat, septic emboli, and others. Additional causes include thrombosis, vasculitis such as giant cell arteritis, vasospasm, trauma, and systemic diseases like sickle cell anemia or autoimmune disorders.
Patients typically present with acute, painless vision loss in one eye. In CRAO, the vision loss is usually severe, often reduced to counting fingers or light perception. In contrast, BRAO may present with partial visual loss, scotomas, or even be asymptomatic if the macula is spared. Some patients report transient vision loss episodes (amaurosis fugax) prior to the event. In older patients, symptoms such as headache, jaw claudication, and scalp tenderness raise concern for giant cell arteritis, which requires urgent evaluation.
On examination, a relative afferent pupillary defect is commonly present, particularly in CRAO. Fundoscopic findings in CRAO include diffuse retinal whitening and edema in the posterior pole with the classic “cherry-red spot” at the fovea. This occurs because the fovea is supplied by the choroidal circulation and remains relatively spared. In BRAO, retinal whitening is localized to the distribution of the affected artery. Emboli may sometimes be visualized within retinal arterioles, and the blood column may appear segmented, known as “boxcarring,” indicating poor perfusion.
Diagnosis involves both ocular and systemic evaluation. Laboratory tests include complete blood count, inflammatory markers such as erythrocyte sedimentation rate and C-reactive protein, lipid profile, and blood glucose. Additional testing may be required to evaluate for hypercoagulable states or infectious causes. Imaging studies such as fluorescein angiography can demonstrate delayed arterial filling, while carotid ultrasound, echocardiography, and electrocardiography are important for identifying the source of emboli. If giant cell arteritis is suspected, urgent temporal artery biopsy is indicated.
Management options for CRAO and BRAO are limited and often yield poor visual outcomes, especially in CRAO. Immediate measures aim to restore retinal perfusion, although their effectiveness is uncertain. These include lowering intraocular pressure with medications such as topical agents or oral acetazolamide, ocular massage to dislodge emboli, and anterior chamber paracentesis. If giant cell arteritis is suspected, high-dose systemic corticosteroids must be initiated immediately to prevent involvement of the fellow eye. Antiplatelet therapy such as aspirin may also be considered.
Long-term management focuses on identifying and controlling systemic risk factors to prevent further vascular events. Patients should be referred for comprehensive cardiovascular evaluation. Follow-up is essential to monitor for complications, particularly neovascularization of the iris or retina, which can lead to neovascular glaucoma. This typically occurs several weeks after the initial event and may require treatment with panretinal photocoagulation or anti-VEGF therapy.
The prognosis differs between CRAO and BRAO. CRAO generally has a poor visual prognosis, with most patients experiencing permanent severe vision loss. In contrast, BRAO has a better outcome, and many patients recover visual acuity to 20/40 or better, especially if the macula is not involved. Complications include neovascular glaucoma, vitreous hemorrhage, and other sequelae of ocular neovascularization.
Early recognition of retinal artery occlusion is critical, not only for potential ocular intervention but also because it may signal underlying systemic vascular disease, including an increased risk of stroke. Prompt multidisciplinary evaluation and management are therefore essential.
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