The effect of timolol-dorzolamide and timolol-pilocarpine combinations on ocular blood flow in glaucomatous patients

Purpose: to investigate the effect of timolol–dorzolamide and timolol–pilocarpine fixed combinations on retrobulbar vessels. Methods: in a prospective, randomized, operator–blind, cross–over clinical trial, 16 patients affected with bilateral Primary Open Angle Glaucoma, treated with timolol 0.5% from at least one month and with IOP <20 mmHg, received in both eyes Timolol 0.5%–Dorzolamide 2% or Timolol 0.5%–Pilocarpine 2% for 4 weeks, and, after 2 weeks of timolol treatment, the other treatment for 4 weeks. Measurements were performed before and after four weeks of treatment, two and twelve hours after the morning dosing. The following parameters were assessed: heart rate, brachial artery blood pressure, intraocular pressure (IOP), peak systolic (PSV) and end–diastolic velocities (EDV) in Ophthalmic Artery (OA), Central Retinal Artery (CRA), temporal and nasal Short Posterior Ciliary Arteries (SPCA). Resistivity index (RI) was calculated. Results: The IOP was significantly reduced by the timolol–dorzolamide combination at 2 hours (p <0.01) and 12 hours (p <0.05), and more effectively by the timolol–pilocarpine combination (both p <0.01). Compared with timolol–pilocarpine, after timolol–dorzolamide treatment, in CRA, at both measurements, EDV was greater and RI was lower (both p<0.01); in temporal and nasal SPCAs, at 12 hours measurement, EDV was greater (p <0.01), while RI was lower (p <0.05) in nasal one. No differences were seen in blood pressure, heart rate and OA velocities.Conclusions: Compared to timolol–pilocarpine combination, timolol–dorzolamide combination increases EDV and reduces RI in CRA and SPCAs, suggesting a positive effect on ocular blood flow.