In this issue of the journal, Kaup et al¹ (see p 1350) report results relating to blood flow dynamics in the ophthalmic artery, the nasal and temporal short posterior ciliary arteries and the central retinal artery in patients in the acute stage of non-arteritic anterior ischaemic optic neuropathy (NAION). Although they are not the first group to conduct such a study, they are the first to compare their findings in patients with NAION with those measured in a group of age-matched controls.

Before commenting on specific results, it is instructive to consider the problem of blood flow and NAION from first principles. As initially described by Henkind et al,² and recently by Arnold³ in his excellent review, histopathological examination shows that there is occlusive vasculopathy in the optic nerve microcirculation located primarily in the retrolaminar region of the nerve head in patients with NAION. The first question, then, is “What is the blood supply to this region?”

The answer to this question is beautifully shown in the …