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

<b>Introduction</b> 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.<p></p> <b>Methods</b> 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.<p></p> <b>Results</b> 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=0.232, P=0.275).<p></p> <b>Conclusion</b> 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

Untreated 24-h intraocular pressures measured with Goldmann applanation tonometry vs nighttime supine pressures with Perkins applanation tonometry

AIMS: To compare supine nighttime intraocular pressure measurements with Perkins applanation tonometry to 24-h sitting intraocular pressures with Goldmann applanation tonometry. METHODS: A prospective, untreated, uncontrolled, observational cohort of qualified consecutive ocular hypertensive or primary open-angle glaucoma patients. Patients underwent sitting intraocular pressure measurements over 24-h by Goldmann and patients had their supine nighttime intraocular pressure measurements by Perkins. RESULTS: In 100 completed patients, the mean intraocular pressure at 1000, 2200, 0200 and 0600 hours while sitting was 22.5+/-3.7 mm Hg, and in the supine position, 23.5+/-4.3 mm Hg (P<0.001). The mean sitting Goldmann intraocular pressures across the three daytime points was 23.3+/-3.4 mm Hg and across three nighttime points was 21.5+/-4.0 mm Hg (P<0.001). In contrast, the mean daytime sitting Goldmann intraocular pressure was not different than the mean nighttime supine intraocular pressure evaluated with Perkins (22.8+/-4.4 mm Hg, P=0.07). However, only 70% of patients were within 1.0 mm Hg of the highest daytime reading for all nighttime supine and sitting intraocular pressures. CONCLUSION: This study suggests that with Perkins applanation tonometry the untreated mean supine intraocular pressures are not higher at night than daytime sitting Goldmann applanation tonometry. However, the highest daytime sitting intraocular pressure measurement does not consistently predict the highest nighttime sitting or supine intraocular pressure valu