['Protein Z is a glycoprotein that acts as a co-factor for the inhibition of activated coagulation factor X. Protein Z circulating in abnormal levels has been associated with increased risk for acute ischemic events. Non-arteritic Anterior Ischemic Optic Neuropathy (N-AION) is caused by acute ischemic infarction of the optic nerve head, supplied by the posterior ciliary arteries.', 'The aim was to investigate whether there is an association between N-AION and plasma protein Z levels.', 'Twenty-six cases of confirmed N-AION and fifty-two controls were included in the study group. Protein Z was estimated in thawed citrate plasma on both N-AION cases and controls by an enzyme immunoassay. The imprecision of the estimation was satisfactory (CV = 4, 6%).', "The controls' protein Z values distributed within a range 340 to 4200 ng/ml (median = 1420, mean = 1673, SD = 1040 ng/ml). Patients' protein Z values distributed within a range 420 to 3600 ng/ml (median = 1030, mean = 1520, SD = 939 ng/ml). There was no statistical difference between the two distributions (Independent t-test, p=0.529)."] Are protein Z Plasma Levels Elevated in Patients with Non-Arteritic Anterior Ischemic Optic Neuropathy?