Ischaemic optic neuropathy: the Singapore scene.

The commonest cause of an optic neuropathy in Singapore is ischaemia, and ischaemic optic neuropathy (ION) is one of the commonest causes of permanent loss of vision in elderly patients, especially in those with diabetes mellitus, hypertension and hyperlipidaemia. ION in our practice is almost invariably of the anterior variety and non-arteritic in origin, i.e. NA-AION. Posterior ION comprises less than two percent of our cases. Three patients with different patterns of NA-AION are described, and in the discussion, how the condition can be distinguished clinically from optic neuritis. With respect to posterior ION, the necessity of excluding a compressive cause before this diagnosis can be made is emphasised.