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

Vitamin A, B(9), 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, B(9), C, E, and antioxidative substance, uric acid in the serum of Japanese patients with normal-tension glaucoma and compare the results with normal controls.

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, B(9), 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.

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 microg/ml control; 6.3 +/- 3.9 microg/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 microg/dl control; 77.1 +/- 30.1 microg/dl), B(9) (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.

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.