Prognosis

The prognosis for recovery of vision is poor, particularly in patients with the arteritic form of ischaemic optic neuropathy. The long term clinical course in non-arteritic ischaemic optic neuropathy is not well documented. In one follow up study of 205 patients, there was a slightly greater incidence of stroke and myocardial infarction than expected but no greater mortality.

Management of acute visual loss

Loss of vision is a common complaint in the emergency department. It may represent a permanent vision threatening disorder. A logical and organised approach to the history and the physical examination is key to the diagnosis. The physician must pay meticulous attention to the following.

• A detailed medical history and the tempo of evolution of visual loss and associated symptoms.

Visual acuity, pupil reflexes, dilated fundoscopic examination.

• Blood pressure, heart rate and rhythm, palpation of the temporal arteries, and auscultation of the heart, neck, eyes, and head.

• Immediate blood tests: complete blood count, prothrombin time, partial thromboplastin time, platelet count, ESR, fibrinogen level, fasting blood sugar, cholesterol, triglyceride, and blood lipids. A test for antiphospholipid antibodies (anticardiolipin antibody and lupus anticoagulant) and measurement of protein C, protein S, and antithrombin III are recommended in unexplained cases of ocular strokes. In these patients a plasma homocysteine and folate levels should be checked.

• Non-invasive investigations:

- Carotid non-invasive studies; useful tests give information about the presence of a haemodynamic lesion (Doppler ultrasonography and oculoplethysmography), analyse the bruit to determine the residual lumen diameter (phonoangiography), or image the artery with ultrasound (B-scan ultrasonography).

- Two-dimensional transthoracic and transoesophageal echocardiography.

• Invasive investigations are required in selected patients:

- A temporal artery biopsy.

- A carotid arteriogram if the patient is a candidate for endarterectomy after non-invasive screening by magnetic resonance angiography and/or CT angiogram of the neck and brain.

- A timed fundus fluorescein angiogram, particularly in cases of central retinal artery occlusion when occlusion of the ophthalmic artery is suspected, in cases of anterior ischaemic optic neuropathy of possible embolic origin, or in giant cell arteritis-associated ischaemic optic neuropathy.

Emergency treatment in central retinal artery occlusion is designed to lower intraocular pressure and dislodge the embolus. In impending central retinal artery occlusion, heparin is useful. Urgent systemic corticosteroids are needed when central retinal artery occlusion or ischaemic optic neuropathy is due to giant cell arteritis. In other situations, treatment is directed towards preventing recurrence or involvement of the other eye by reducing or eliminating risk factors.

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