The authors evaluate the monocyte to high-density lipoprotein (HDL) ratio (MHR) in patients with arteritic and non arteritic anterior ischaemic optic neuropathy (A-AION / NA-AION). A distinction between the two types of AION is essential to begin appropriate treatment, which can be adapted according to the aetiology. This study evaluates the relationship between the two principal causes of AION and inflammation by analysing MHR. The 98 subjects recruited were divided into three groups: 16 with A-AION (group one), 41 with NA-AION (group two) and 41 healthy controls. The mean MHR was significantly higher only in the A-AION group compared with the NA-AION and control group (p<0.001). There was no difference between the NA-AION group and control group (p=0.110). On receiver operating characteristic analysis, the area under the curve was 0.755, and the best cut-off value was 12.2 with a sensitivity of 72% and specificity of 80%. The authors conclude that, as an elevated MHR ratio is significantly associated with A-AION, the MHR could be used to differentiate between A-AION and NA-AION.