Otherwise, even if no retinal emboli are identified on ophthalmoscopy, urgent investigation for carotid and cardiac sources of emboli must be undertaken in central and particularly in branch retinal artery occlusion, so that timely treatment can be given to reduce the risk of stroke (see Chapters 12, 14, and 24) Diabetes mellitus, hyperlipidemia, and systemic hypertension are common etiologic factors Migraine, oral contraceptives, systemic vasculitis, congenital or acquired thrombophilia, and hyperhomocysteinemia are also causes, particularly in young patients Internal carotid artery dissection should be considered especially when there is neck pain or a recent history of neck trauma

Clinical Findings

A Symptoms and Signs Central retinal artery occlusion presents as sudden profound monocular visual loss Visual acuity is usually reduced to counting fingers or worse, and visual field is restricted to an island of vision in the temporal field Ophthalmoscopy reveals pallid swelling of the retina with a cherry-red spot at the fovea The retinal arteries are attenu- ated, and “box-car” segmentation of blood in the veins may be seen Occasionally, emboli are seen in the central retinal artery or its branches The retinal swelling subsides over a period of 4–6 weeks, leaving a pale optic disk with thinning of the inner retina on optical coherence tomography scans Branch retinal artery occlusion may also present with sudden loss of vision if the fovea is involved, but more commonly sudden loss of visual field is the presenting complaint Fundal signs of retinal swelling and sometimes adjacent cotton-wool spots are limited to the area of retina supplied by the occluded artery Identify risk factors for cardiac source of emboli including arrhythmia, particularly atrial fibrillation, and cardiac valvular disease, and check the blood pressure Nonocular clinical features of giant cell arteritis are age 50 years or older, headache, scalp tenderness, jaw claudication, general malaise, weight loss, symptoms of polymyalgia rheumatica, and tenderness, thickening, or absence of pulse of the superficial temporal arteries Table 20–12 lists the clinical manifestations of vasculitis B Laboratory Findings Erythrocyte sedimentation rate and C-reactive protein are usually elevated in giant cell arteritis but one or both may be normal Consider screening for other types of vasculitis Screen for diabetes mellitus and hyperlipidemia in all patients Particularly in younger patients, consider testing for antiphospholipid antibodies, lupus anticoagulant, inherited thrombophilia, and elevated plasma homocysteine C Imaging To identify carotid and cardiac sources of emboli, obtain duplex ultrasonography of the carotid arteries, ECG, and echocardiography, with transesophageal studies (if necessary) When indicated, obtain CT or MR studies for internal carotid artery dissection

Treatment

If the patient is seen within a few hours after onset, emergency treatment, comprising laying the patient flat, ocular massage, high concentrations of inhaled oxygen, intravenous acetazolamide, and anterior chamber paracentesis, may influence the visual outcome Early thrombolysis, particularly by local intra-arterial injection but also intravenously, has shown good results in central retinal artery occlusion not due to giant cell arteritis, but the former method has a high incidence of adverse effects and may be difficult to accomplish within the required time In giant cell arteritis, there is risk of involvement of the other eye without prompt treatment Recommended initial empiric treatment is intravenous methylprednisolone 0 5–1 g/day for 1–3 days but intravenous hydrocortisone 250–500 mg may be easier to administer Whether oral methylprednisolone is similarly effective is unknown All patients require subsequent long-term corticosteroid therapy (eg, oral prednisolone 1–1 5 mg/kg/day) and possibly low-dose aspirin (~81 mg/day orally) There must be close monitoring to ensure that symptoms resolve and do not recur Temporal artery biopsy should be performed promptly, and if necessary, assistance sought from a rheumatologist Patients with embolic retinal artery occlusion and 70–99% ipsilateral carotid artery stenosis and possibly those with 50–69% stenosis should be considered for carotid endarterectomy or possibly angioplasty with stenting to be performed within 2 weeks Retinal embolization due to cardiac disease such as atrial fibrillation or a hypercoagulable state usually requires anticoagulation Cardiac valvular disease and patent foramen ovale may require surgical treatment

When to Refer

Patients with central retinal artery occlusion should be referred emergently to an ophthalmologist

Patients with branch retinal artery occlusion should be referred urgently

When to Admit Patients with visual loss due to giant cell arteritis may require emergency admission for high-dose corticosteroid therapy and close