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Ischemic Optic Neuropathy

Ischemic neuropathy

Swollen optic disc
The margins of the optic disc are fuzzy, and there are cotton wool spots on the superior border. These signs tell you that axoplasm is not flowing normally through the optic nerve.

In this patient, there has been an infarction owing to impaired blood flow, but many other conditions can cause a swollen disc (increased intracranial pressure, inflammation, and infiltration by cancer cells, for example). You cannot tell the cause of the swelling merely by looking at it.

Ischemic optic neuropathy
This is the term used to designate infarction of the optic nerve. The usual cause is small vessel arteriosclerosis in a patient with hypertension. Individuals aged between 40 and 80 are at risk. There is no treatment.

Infarction of the optic nerve is also the typical finding in giant cell (temporal) arteritis, an autoimmune disorder affecting medium-sized arteries in patients aged over 60 years. They often have one or more symptoms from two complexes: 1) polymyalgia rheumatica: malaise, limb girdle aches, and poor appetite; and 2) external carotid hypoperfusion: headache, scalp tenderness, and pain on chewing.

The disease is caused by inflammatory occlusion of blood vessels, and the diagnosis is urgent, because if the patient is not treated, there is a good chance that the other optic nerve will become infarcted within days. Diagnosis is based on finding inflammation on biopsy of the temporal artery. It shows fragmentation of the internal elastic lamina and sometimes Langerhans giant cells.

Treatment consists of oral prednisone 1.5 mg/kg/day or intravenous methylprednisolone 1-2 gm/day. Temporal artery biopsy is performed within 1 week of starting treatment. Treatment often prevents infarction of the second eye, but does not reverse damage due to a pre-existing infarction.

What to do?
Refer immediately to an ophthalmologist. In the elderly, giant cell arteritis is a consideration. Emergent high-dose corticosteroid treatment cannot restore vision but can markedly reduce the chances that the fellow eye will develop an optic nerve infarction.

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