Anterior ischaemic optic neuropathy: I. Terminology and pathogenesis

Abstract

The clinical entity comprising sudden loss of vision, initially associated with oedema of the optic disc, which resolves to optic atrophy within a month or two, leaving a permanent visual defect, has been given many different names. It is suggested that the term "Anterior Ischaemic Optic Neuropathy" (AION) gives an accurate description. A theory of its pathogenesis based on clinical, experimental, and histopathological evidence is discussed. The evidence shows that interference with the posterior ciliary artery (PCA) supply to the anterior part of the optic nerve is responsible for AION, without involvement of the central retinal artery. It is not essential for the PCAs to be completely occluded to produce AION, because, as soon as the perfusion pressure in the PCAs falls below the intraocular pressure for any reason (e.g. local vascular, systemic, and ocular causes), the blood supply to the anterior part of the optic nerve is cut off because of its special vulnerability to such an occlusion. The mechanism of this process is discussed.