Anterior ischaemic optic neuropathy. I. Terminology and pathogenesis.

Abstract

In anterior ischaemic optic neuropathy (AION) there is a comparatively sudden loss of vision in the entire eye, or in one sector of the field of vision of the eye, initially associated with oedema of the optic disc, which results in optic atrophy within a month or two, leav- ing a permanent visual defect.A large number of such cases have been reported in the literature, but, although this clinical entity is well-known under different names, its pathogenesis and management have till recently been ill-understood.A full understanding of the pathogenesis of AION would make it considerably easier to understand its clinical pattern and management. TerminologyThis condition has been given different eponyms by various authors because of controversy as to its pathogenesis (Hayreh, I974c).The most popular term in the European literature has been "vascular pseudo-papillitis" (Fransois, Verriest, and Baron, I956, I957) and in the English "ischaemic optic neuro- pathy".As will be evident from the pathogenesis of this condition, perhaps the most suitable term is "anterior ischaemic optic neuropathy"; because the condition is ischaemic, involves both the optic nerve head and retrolaminar optic nerve (hence the terms defining it as a disease only of the optic disc are not correct), non-inflammatory (therefore all terms in- cluding the suffix -itis are incorrect), and there is nothing "pseudo-" about it. Pathogenesis Many theories have been postulated to explain the pathogenesis.A review of the literature (Hayreh, I974c) reveals that the site of the lesion in AION is thought to lie in the optic nerve, although some authors considered it to be due to involvement of the retina.It is almost universally agreed that the condition is the result of interference with the circulation of one of these structures.The vast majority of authors, while describing a circulatory lesion in the optic nerve, have made vague statements without being specific as to the exact lesion.However, Fransois and co-workers (Francois and others, 1957; Francois, Verriest, Neetens, and De Rouck, I96I; Francois, Verriest, De Rouck, and Hanssens, i962; Francois and Neetens i969) postulated that AION was due to occlusion of the so-called "central artery of the optic nerve", an artery they only assumed to exist (Franqois and Neetens, 1954, 1956; Frangois, Neetens, and Colette, I955).My anatomical studies on the blood supply of the optic nerve and branches of the ophthalmic artery in about one hundred human specimens (Hayreh, I958, I962, I 963a,b; Singh and Dass, I g60a,b) and those of Beauvieux and Ristitch (1924) and Steele and Blunt (I 956) failed to reveal the presence of any "central artery of