RETROBULBAR ARTERIAL HEMODYNAMIC-EFFECTS OF BETAXOLOL AND TIMOLOL IN NORMAL-TENSION GLAUCOMA

PURPOSE: beta-Adrenergic blocking drugs lower intraocular pressure, Th e question of whether these drugs also alter, either directly or indir ectly, orbital hemodynamics is potentially of great importance for pat ients with normal-tension glaucoma who may have some degree of reversi ble vasospasm. METHODS: We compared the effect of selective (betaxolol ) and nonselective (timolol) p-adrenergic blocking drugs on flow veloc ities (as determined by color Doppler imaging) in orbital vessels in 1 3 patients with normal-tension glaucoma (mean age, 62 +/- 3 years; mea n intraocular pressure, 15 +/- 2 mm Hg), A one-month drug treatment do uble masked crossover design, with a three-week washout before each dr ug, was used. RESULTS: Neither drug changed peak systolic velocity in any of the four vessels studied (ophthalmic, nasal and temporal poster ior ciliary, and central retinal arteries), Additionally, timolol did not alter end-diastolic velocity or resistance index (defined as [peak systolic velocity minus end-diastolic velocity] divided by peak systo lic velocity) in any of the vessels measured, In contrast, betaxolol t ended to increase end diastolic velocity and to decrease resistance in dex: the four-vessel average end-diastolic velocity increased 30% (P = .08), and the four-vessel average resistance index decreased signific antly (P = .04). These reductions in resistance index occurred despite that betaxolol, in contrast to timolol, did nor significantly decreas e intraocular pressure. CONCLUSIONS: These results suggest that, in pa tients with normal-tension glaucoma, selective beta-adrenergic blockad e (betaxolol) may have ocular vasorelaxant. effects independent of any influence on intraocular pressure, whereas nonselective blockade (tim olol) lowers intraocular pressure without apparently altering orbital hemodynamics.