Anterior ischaemic optic neuropathy: what do we know and what do we still need to know?

Anterior ischaemic optic neuropathy (AION) is the most frequent cause of unilateral papillary edema in patients over 45 years of age. Two main entities can be differentiated in AION: the non-arteritic form (NAION) which constitutes 96% of cases and has an estimated incidence in the USA of 2.3– 10.2 cases for every 100,000 inhabitants1; and the arteritic form (AAION), considered to be an additional expression of giant cell arteritis (GCA) or Horton’s arteritis.2 Even though this latter form exhibits much lower frequency, it constitutes one of the main ophthalmological emergencies, to the extent that early diagnosis and intervention can determine the involvement of the contralateral eye and accordingly the final visual prognosis. AION is a pathology that routinely appears in emergency services and involves a differential diagnosis with other causes of optic disc edema. In some cases it requires joint responsibility between the ophthalmology, neurology and internal medicine services and this requires adequate training for each specialist who should have sufficient knowledge and resources to act quickly and adequately in each case. At present, NAION remains a controversial issue in various aspects. The most accepted physiopathology for this process is circulatory insufficiency at the optic nerve head. However, the exact mechanism that causes this insufficiency is not yet known. The most widely accepted theory in idiopathic