A comparative study of the effects of brinzolamide and dorzolamide on retinal oxygen saturation and ocular microcirculation in patients with primary open-angle glaucoma.

AIMS: To assess the effects of brinzolamide and dorzolamide on ocular haemodynamics and retinal oxygen saturation in patients with primary open-angle glaucoma (OAG).

METHODS: Fifteen patients with OAG were evaluated in a randomised, cross-over, double-blind study. They were treated with either brinzolamide or dorzolamide for 3 months and then crossed-over after a 4-week washout period. They were given timolol during a 4-week run-in period and during washout. The following were performed after run-in, after washout and after each treatment period: adverse events check, measurement of visual acuity, contrast sensitivity, blood pressure, heart rate, and intraocular pressure, and fundus examination. Ocular blood flow was assessed using confocal scanning laser Doppler flowmetry (HRF) and colour Doppler imaging (CDI). Retinal oxygenation levels were determined using a non-invasive measurement of haemoglobin oxygen saturation by digital photographic fundus oximetry.

RESULTS: Both brinzolamide and dorzolamide reduced the number of zero-flow pixels in the retina as measured by HRF, suggesting an increase in retinal blood flow (-6.86 and -0.452 respectively) with brinzolamide treatment resulting in fewer zero-flow pixels than dorzolamide (-6.41) (p = 0.024). Both brinzolamide and dorzolamide increased oxygen saturation in the retina as measured by photographic retinal oximetry in the superior (0.82 (p = 0.002) and 0.87 (p = 0.005)) and inferior (0.88 (p = 0.035) and 0.82 (p = 0.002)) retinal veins. No significant changes were found in CDI measurements of the retrobulbar blood supply during either treatment.

CONCLUSION: This pilot study suggests that brinzolamide and dorzolamide may increase retinal oxygen saturation in patients with OAG.