Ocular blood flow and oxygen delivery to the retina in primary open‐angle glaucoma patients: the addition of dorzolamide to timolol monotherapy

Abstract

To assess the effects of adding dorzolamide to timolol monotherapy on ocular haemodynamics and retinal oxygen saturation in patients with primary open-angle glaucoma (POAG). Twenty-four patients (12 healthy, 12 with POAG) were treated with dorzolamide/timolol combination (DT) versus timolol maleate 0.5% twice daily in a randomized, crossover, double-blind study conducted over a period of 18 months. Patients received each treatment for 8 months then crossed over to the other treatment after a 1-month washout and second baseline. Goldmann applanation tonometry, Heidelberg retinal flowmetry (HRF), colour Doppler imaging (CDI) and retinal photographic oximetry were performed at each visit. DT significantly reduced intraocular pressure (IOP) in both glaucomatous [right eye (OD) -13.15%, left eye (OS) -14.43%; p < 0.036] and non-glaucomatous (OD -12.4%, OS -13.88%; p < 0.039) patients compared to timolol after 8 months of treatment. DT significantly reduced the number of zero blood flow pixels in the superior (-39.72%; p < 0.014) and inferior (-51.44%; p < 0.008) retina in the non-glaucomatous group and inferior retina in the glaucomatous group (-55.38%, p < 0.006). The continuation of timolol monotherapy from baseline did not change (p < 0.05) any measured parameter and neither treatment had a significant effect (p < 0.05) on retinal oximetry or CDI parameters. The addition of dorzolamide to timolol monotherapy decreases IOP and increases retinal blood flow in the superficial retinal vasculature in both glaucomatous and healthy patients following 8 months of treatment. The combination of increased retinal blood flow with consistent oxygen saturation may potentially increase oxygen delivery to the retina.