Ischaemic damage to the optic nerve is caused by reduced blood flow. It is a common sudden-onset disorder of the optic nerve in patients over 50, and also a cause of severe sight loss in adults with glaucoma.
Ischaemic optic nerve damage is classified by the part of the optic nerve it affects (that is, the anterior or the posterior portion), with most injuries caused by reduced blood flow affecting the anterior part of the nerve. This common type of optic neuropathy is aptly called non-arteritic anterior ischaemic optic neuropathy (NAION), because the reduced blood flow that damages the optic nerve is not associated with a local pathological process in the blood vessels (inflammation or a clot, for example).
It usually causes sudden, painless loss of sight that develops over a matter of hours to days and is often described as blurred or dim vision with pronounced clouding and profound visual field defects. In many cases the sight loss remains fairly stable, with little or no improvement. Only about 35 % to 40 % of patients experience spontaneous partial improvement in visual acuity. In addition, patients who develop NAION in one eye only carry a 15 % to 19 % risk of developing a similar condition in the fellow eye within roughly five years.
This condition is also a suitable candidate for electrostimulation.