Purpose
We have previously reported that level of systemic antioxidant capacity is lower in open angle glaucoma patients than non-glaucomatous controls. Here we assessed the correlation between IOP and systemic levels of prooxidants and antioxidants by analyzing the blood biochemistry in patients with glaucoma.
Methods
Peripheral blood samples were collected from Japanese patients with primary open-angle glaucoma (PG) (n=206), exfoliation syndrome (EX) (n=199), and controls (n=126). Serum levels of lipid peroxides, ferric-reducing activity, and thiol antioxidant activity were measured by diacron reactive oxygen metabolites (dROM), biological antioxidant potential (BAP), and sulfhydryl (SH) tests, respectively, using a free radical analyzer. To test the possible effect of oxidative stresses on IOP levels, entire subjects were classified into 4 groups (Q1, Q2, Q3, and Q4; Q1 is the lowest IOP group) based on the quartile value of IOP. For this classification, the known highest IOP in both right and left eyes were taken as each subject’s IOP. For comparisons among IOP groups, the differences were calculated using one-way analysis of variance followed by post-hoc un-paired t tests. To adjust for differences in demographic characteristic distributions, the values of the dROM, BAP, and SH tests were compared between the IOP groups using multiple logistic regression analysis; the odds ratio of each variables were calculated as the Q1 group was a reference.
Results
The dROM (p=0.6704) and the SH (p=0.6376) levels did not differ significantly between 4 IOP groups. The BAP levels were significantly different among 4 IOP groups (p=0.0115); the value is significantly lower in the Q4 (1,932 µmol/L) than the Q1 (2,023 µmol/L, p=0.0042) and Q2 (2,003 µmol/L, p=0.0302) groups, and in the Q3 (1,948 µmol/L) than Q1 (p=0.0174) groups. After adjustment for differences in various demographic characteristics, lower BAP values significantly associated with the classification into higher IOP groups (p=0.0261 and OR=0.06/range for Q3 group, and p=0.0018 and OR=0.04/range for Q4 group); The dROM and SH values did not reach statistical significance in any comparisons.
Conclusions
Lower systemic antioxidant capacity that measured by ferric-reducing activity is involved in the pathogenesis of PG and EX via its roles of IOP elevation.