Changing antiglaucoma therapy from timolol to betaxolol: effect on ocular blood flow

The aim of the present study was to investigate the effect of a therapy change from timolol to betaxolol on ocular blood flow in patients with open-angle glaucoma. This randomized double-blind study comprised 34 consecutive patients with open-angle glaucoma, already treated with either timolol alone or in combination with other antiglaucoma agents. The patients were randomly allocated to receive either betaxolol (n = 17) or timolol (n = 17) instead of the present timolol drops. Additional antiglaucoma therapy remained unchanged. The retinal blood flow was assessed by scanning laser Doppler flowmetry and the pulsatile choroidal blood flow was assessed by laser interferometric measurement of fundus pulsation amplitude. Ocular blood flow measurement as well as systemic hemodynamic and intraocular pressure (IOP) measurements were performed at baseline and 1 week and 1 and 3 months after the therapy change. Visual field testing was performed at baseline and at 3 months. After 3 months of treatment with either timolol or betaxolol, neither the retinal nor the pulsatile choroidal blood flow were significantly altered. The power to detect a 9% change in pulsatile choroidal blood flow and a 20% change in retinal blood flow in the present study was 90%. The IOP was not significantly altered in either group. In contrast, visual fields slightly improved after betaxolol treatment compared to baseline (p = 0.047), but this effect was not significant versus timolol. Changing therapy from timolol to betaxolol has no effect on ocular blood flow in patients with open-angle glaucoma.