Aspirin following non-arteritic ischaemic optic neuropathy-a systematic review and meta-analysis

A debate exists whether aspirin should be recommended following the occurrence of non-arteritic anterior ischaemic optic neuropathy (NAION). Possible benefits of aspirin following NAION include lowering the risk for second-eye occurrence and reducing the risk of myocardial infarction or of cerebral infarction. The aim of the present study is to answer the question whether aspirin should be recommended to patients following NAION. A search of MEDLINE and the Cochrane Library (1950-2006) was undertaken for comparative studies assessing the efficacy of aspirin in the prevention of second eye NAION. We also reviewed studies concerning the incidence of myocardial or cerebral infarction following NAION and the prevalence of NAION patients meeting guidelines for aspirin as primary prevention. From the combined data we calculated the point estimate of the relative risk for second-eye NAION, the number-needed-to-treat to prevent one second-eye NAION and compared this number to the reported incidence of severe haemorrhagic complications of aspirin therapy. The point estimate for the relative risk (RR) calculated from a synthesis of the four observational studies is in favour of protection by aspirin (RR = 0.62; 95% CI 0.36-1.07). However the confidence interval is wide and includes unity. No randomized controlled trial has been conducted. The incidence of myocardial and cerebral infarction following NAION seems to be higher than in the general age-matched population. Data suggest a benefit of aspirin in prevention of second eye NAION, but the evidence is weak. A multi-centre randomized controlled trial recruiting 750 patients is unlikely to be feasible.