Reduced-serum vitamin C and increased uric acid levels in normal-tension glaucoma

Background: Vitamin A, B₉, C, E, and uric acid are well-known antioxidants and may prevent age-related eye disorders. The aim of the present study was to investigate the levels of antioxidant vitamins, A, B₉, C, E, and antioxidative substance, uric acid in the serum of Japanese patients with normal-tension glaucoma and compare the results with normal controls. Methods: All subjects with suspicion of primary open-angle glaucoma who came to the glaucoma subspeciality clinic of Keio University Hospital were enrolled in this study. Sixty patients (28 males, 32 females; mean age ± standard deviation: 59.9 ± 9.8 years) with newly diagnosed primary open-angle glaucoma patients were consecutively enrolled in this study. After the diagnosis of primary open-angle glaucoma, the patients underwent 24-h IOP measurements. Forty-seven newly diagnosed consecutive normal-tension glaucoma patients (18 males, 29 females; mean age ± standard deviation: 59.5 ± 10.2 years) were enrolled in this study. The control subjects were recruited from subjects who came to the clinic for annual refractive check-up. The 44 consecutive control subjects of the current study, (16 males, 28 females; 62.7 ± 14.8 years) did not have any ocular diseases. The serum levels of vitamins A, B₉, C, E, and uric acid were measured. The values were compared between the normal-tension glaucoma and control groups by the Mann-Whitney U test. Results: Serum levels of vitamin C were significantly lower in normal-tension glaucoma patients than in normal healthy controls (P = 0.04; normal-tension glaucoma; 4.6 ± 4.0 μg/ml control; 6.3 ± 3.9 μg/ml). Uric acid level was significantly higher in normal-tension glaucoma patients than in controls (P = 0.01; normal-tension glaucoma; 5.8 ± 1.5 mg/dl control; 4.9 ± 1.4 mg/dl). No statistically significant difference was seen in vitamin A (P = 0.41; normal-tension glaucoma; 82.1 ± 26.7 μg/dl control; 77.1 ± 30.1 μg/dl), B₉ (P = 0.37; normal-tension glaucoma; 8.7 ± 4.3 ng/ml control; 8.0 ± 3.1 ng/ml)and E (P = 0.83; normal-tension glaucoma; 1.5 ± 0.6 control; 1.5 ± 0.6) levels between normal-tension glaucoma and control groups. Conclusion: Normal-tension glaucoma patients had lower serum levels of vitamin C and increased levels of uric acid. These observations may pave the way for possible alternative treatment for normal-tension glaucoma.