Ascorbic acid concentration is reduced in the secondary aqueous humour of glaucomatous patients

Abstract

Background: We aimed to evaluate the ascorbic acid concentration in secondary aqueous humour (AH) from glaucomatous patients and to compare it with primary AH from primary open‐angle glaucoma patients and non‐glaucomatous patients. Methods: Primary AH samples were prospectively obtained from clinically uncontrolled primary open‐angle glaucoma patients and senile cataract patients (controls) prior to trabeculectomy and cataract surgery. Secondary AH samples were obtained from eyes with previous intraocular surgery, prior to trabeculectomy or cataract surgery. AH (0.1 mL) was aspirated by inserting a 26‐gauge needle into the anterior chamber just before surgery and then immediately stored at −80°C. The ascorbic acid concentration was determined in a masked fashion by high‐pressure liquid chromatography. Results: A total of 18 patients with senile cataract, 16 glaucomatous patients with primary AH (no previous intraocular surgery) and 11 glaucomatous patients with secondary AH (previous intraocular surgery) were included. There was no difference in mean age between groups (P = 0.15). The mean ± standard deviation concentration of ascorbic acid in the secondary AH from glaucomatous patients (504 ± 213 µmol/L [95% confidence interval {CI}, 383–624]) was significantly lower than the concentration of ascorbic acid found in the primary aqueous of primary open‐angle glaucoma (919 ± 427 µmol/L [95% CI, 709–1128]) and control patients (1049 ± 433 µmol/L [95% CI, 848–1249]; P < 0.01, Kruskal‐Wallis test). Conclusions: The ascorbic acid concentration in secondary AH of glaucomatous patients was approximately twofold lower in comparison with primary AH of glaucomatous and cataract patients. The implications of a reduced concentration of ascorbic acid in the secondary AH deserve further investigation.

Ascorbic acid concentrations in aqueous humor after systemic vitamin C supplementation in patients with cataract: pilot study

“…For example, the concentration of vitamin C was reported to decrease with age in patients with age-related cataract, suggesting that reductions in ascorbic acid may play an important role in cataract formation [4, 5]. Lower levels of vitamin C in aqueous humor may be associated with glaucoma, including in patients with primary open angle glaucoma and secondary glaucoma [8, 9, 16]. Finally, patients with Lowe’s syndrome and exfoliation syndrome have significantly lower levels of ascorbic acid in aqueous humor than age-matched controls [6, 8].…”

“…Moreover, oral, topical or intravenous application of vitamin C lowers intraocular pressure in glaucoma patients [8, 9, 19]. The Age-Related Eye Disease Study (AREDS) found that long-term supplementation with vitamin C (500 mg/day) and other vitamins was effective in retarding the progression of age-related macular degeneration (AMD) [20] and in delaying the progression of lens opacities [4, 18].…”

“…For example, the concentration of vitamin C in the anterior chamber has been reported lower in patients with Lowe’s syndrome and exfoliation syndrome than in age-matched controls [6–8]. Moreover, reduced levels of vitamin C in aqueous humor may be associated with glaucoma [8, 9]. Thus, measuring vitamin C concentrations in aqueous humor may be useful for studying the pathogenesis of several ocular diseases.…”

Ascorbic Acid Modulation of Iron Homeostasis and Lysosomal Function in Trabecular Meshwork Cells

“…Similarly, a reduction of the levels of vitamin C in plasma as well as in the AH of patients with POAG and secondary glaucoma has also been documented by several investigators. [10][11][12] Additional evidence of the potential relevance of AA in outflow pathway physiology and pathophysiology comes from the observed IOP-lowering effect of AA, [4][5][6] and from the recent work by Zanon-Moreno et al 14 reporting an association between a polymorphism in the AA transporter SLC23A2 with lower plasma concentrations of AA and with higher risk of POAG. Based on the data obtained here, it is plausible that such diminished levels of ascorbate or deficient AA cellular uptake can compromise lysosomal degradation in the outflow pathway cells with aging and contribute to the pathogenesis of glaucoma.…”

“…[7][8][9] Several investigators have reported reduced levels of AA in the AH of patients with primary open-angle glaucoma (POAG) and secondary glaucomas. [10][11][12] Lower AA plasma concentrations have also been found in POAG patients as well as in patients with normal-tension glaucoma. 13,14 Very interestingly, a very recent study has demonstrated a significant association between a polymorphism in the AA transporter SLC23A2 with such lower plasma concentrations of AA and with higher risk of POAG.…”