Ischaemic optic neuropathy

This describes sudden loss of vision, altitudinal visual field defects - more commonly inferior than superior - and a pale, swollen disc due to occlusion of the short posterior ciliary arteries. These arteries supply the retrolaminar cribrosa area, posterior to the optic nerve head where the optic nerve capillaries are less abundant. Small 'splinter' haemorrhages are common. Examination reveals an afferent pupillary defect.

There are two types:

• idiopathic - typically in diabetics or hypertensives; not treatable
• arteritic - principally, giant cell arteritis; usually bilateral and treatable by high dose steroids