Free radicals and the pH of topical glaucoma medications: a lifetime of ocular chemical injury?

Abstract

Introduction Preservatives in ophthalmic preparations are known to cause ocular surface damage. Excipients can also contribute to oxidative stress in the compromised ocular surface. We evaluated commonly used topical glaucoma medications to ascertain pH levels and the intrinsic presence of free radicals. Methods Samples of 27 topical glaucoma preparations were analysed for total free radical presence using a Randox Kit for total antioxidant status. Analytical grade indicator paper was used to ascertain pH levels. Results Free radical concentrations for these 27 glaucoma preparations ranged from 0 to 4.54 mmol/l, with a median value of 0.66 mmol/l (mean value of 0.662 mmol/l, SD 0.839). Levels of pH ranged from 4.0 to 7.4, with a median value of 6.5 (mean 6.252, SD 0.826). There was no evidence of a direct correlation between these two variables (r ¼ 0.232, P ¼ 0.275). Conclusion This study is the first to document the range of pH and concentrations of free radicals intrinsically present in commonly used glaucoma medications. Long-term exposure to preservatives, free radicals, and pH levels could all contribute to ocular surface damage. The effect of excipients could be responsible for patient intolerance when changing products in the compromised ocular surface.

EDTA chelation for symptomatic band keratopathy: results and recurrence

“…[16][17][18][19] We have previously published on the potential detrimental impact of chronic excipient exposure in glaucoma patients, best considered to be a low grade 'lifelong chemical injury' related to the pH and chronic free radical damage from their ocular anti-hypertensives. 20,21 Both superficial and deep band keratopathy have been linked with the presence of phosphate excipients in topical ophthalmic medications. 22 Popiela et al surveyed 78 commonly used ophthalmic medications for information regarding their excipients, and discovered that 22 of the drugs contained phosphates, and a further 43 drugs contained buffers (excipients) other than phosphates.…”

Clinical outcomes of xeno-free expansion and transplantation of autologous ocular surface epithelial stem cells via contact lens delivery: a prospective case series

“…Additional investigations are required to determine whether glaucoma medication could be revised prior to and during a specific period post-cell therapy to increase the survival probability of grafts in patients with coexisting severe glaucoma. Indeed, since our study commenced, a wider range of glaucoma medications with less potential for ocular surface toxicity have become available [ 49 ].…”

Antioxidant properties of amniotic membrane: novel observations from a pilot study

“…Intrinsic free radical presence has been reported in topical and intracameral ophthalmic preparations, independent of preservatives or pH. [41][42][43] Low grade chronic oxidative stress could explain residual inflammation in vulnerable ocular surfaces even when using long term unpreserved medications.…”