This review article describes nonarteritic anterior ischaemic optic neuropathy (NAION). This condition is one of the common causes of visual loss in adults. The article uses a good range of references and is divided under the headings of; demographics, clinical presentation, pathophysiology, pathogenesis, risk factors, cellular mechanisms, clinical course, differential diagnosis, diagnostic testing, therapy and prevention. NAION typically presents in patients over 50 years as acute painless unilateral visual loss associated with an inferior visual field defect, swollen optic disc and flame-shaped peripapillary retinal haemorrhages. Visual acuity tends to be better than 6/60 likely due to impaired blood flow in the optic nerve vasculature. Patients tend to have at least one underlying vascular risk factor such as nocturnal systemic hypotension, systemic hypertension or diabetes. The risk factor section is of particular interest and well referenced. NAION remains stable over time with some reported cases of spontaneous improvement. The role of differential diagnosis is highlighted and complemented by diagnostic testing. Although there is no consistent treatment for this condition the authors offer a detailed insight into published work and list the limitations of the current literature. Overall this article offers an excellent review of NAION.