EFFECT OF TOPICAL BETA-BLOCKERS ON TISSUE BLOOD-FLOW IN THE HUMAN OPTIC-NERVE HEAD

Purpose. To study the effect of topical 0.5% timolol and 2% carteolol on tissue blood flow in the human optic nerve head (ONH). Methods. Usi ng a laser speckle tissue blood flow analyzer, normalized blur (NB), a quantitative index of tissue blood velocity, was measured every 0.125 s in the temporal site of the ONH free of visible surface vessels and averaged over 3 cardiac pulses (NBONH) TO serve as a baseline, NBONH and intraocular pressure (IOP) in both eyes, blood pressure (BP) and p ulse rate (PR) were recorded in healthy volunteers before, 1.5, 3 and 4.5 hrs after a 30L instillation of the vehicle of timolol or carteolo l. From the following day and twice daily for 3 weeks, 30L of either 0 .5% timolol or 2% carteolol was instilled into one eye and the respect ive vehicle into the fellow eye in a masked manner. NBONH, IOP BP and PR were again recorded on the 21st and last experiment day. IOP was al so recorded on the 7th and 14th days. Carteolol concentration in the p lasma was also recorded after instillation of carteolol on the 21st da y. Results. During the baseline experiments, all the parameters record ed showed no significant change. After topical timolol, IOP was signif icantly reduced bilaterally with more reduction in the timolol-treated eye. Bilateral NBONH, BP and PR showed Little change on the 21st day. After topical carteolol, IOP was significantly reduced bilaterally wi th more reduction in the carteolol-treated eyes on the 21st day. NBONH in the carteolol-and vehicle-treated eyes was significantly higher on the 21st day than recorded in the same eye in the baseline experiment (P = 0.013 and 0.047), while BP and PR showed little change. The maxi mum carteolol concentration in plasma at 3 hrs on the 21st day average d 1294 pg/ml. Conclusions. Results indicated that 3-week twice daily t opical timolol treatment had no deleterious effect on the ONH tissue b lood flow in the human eye, and that 3-week twice daily topical carteo lol treatment may increase the tissue blood flow in the human ONH.