The two main entities of open-angle glaucoma are primary open-angle glaucoma (POAG) and normal tension glaucoma (NTG). Both diseases may be associated with autoimmune processes. Therefore, IgG and IgM antibodies to phospholipids (APL) and their subspecies cardiolipin (ACL), phosphatidylserine (APS) and beta2-glycoprotein (beta2GP) were determined in 43 NTG patients, 40 POAG patients and 40 healthy controls in a prospective study. The most prominent observation was the increase in APS concentrations in NTG patients (IgG 20.6 +/- 2.7 U/ml, IgM 24.4 +/- 3.4 U/ml) compared with POAG patients (IgG 8.8 +/- 1.2 U/ml, IgM 11.0 +/- 1.7), and controls (IgG 7.7 +/- 1.3 U/ml, IgM 12.8 +/- 1.5 U/ml). APS may be important due to their binding specificity to phosphatidylserine molecules which become accessible during apoptosis; this in turn may lead to local thrombosis.