The thiol-disulfide balance is very important in cellular events such as apoptosis and oxidative stress. This study is a comparison of plasma thiol-disulfide homeostasis in patients with pseudoexfoliation syndrome (PEXS) and pseudoexfoliation glaucoma (PEXG).Thirty-one patients with PEXS, 43 patients with PEXG, and 38 healthy controls were included in this prospective study. The plasma level of native thiol and disulfide were measured using a spectrophotometric assay and the native thiol/disulfide ratio was analyzed.The demographic characteristics of the 3 groups were similar (p>0.05). Statistically significant differences were observed in the plasma disulfide levels (21.6±7.3 µmol/L vs. 17.4±6.8 µmol/L) and the native thiol/disulfide ratio (22.9±9.1 vs. 29.9±14.7) between the PEXG group and the controls (p=0.03, p=0.02, respectively).Significant differences in the plasma levels of disulfide and the native thiol/disulfide ratio in PEXG patients indicated a breakdown of the thiol-disulfide circuits.