EFFECTS OF TOPICAL ADRENERGIC AGENTS ON TISSUE CIRCULATION IN RABBIT AND HUMAN OPTIC-NERVE HEAD EVALUATED WITH LASER SPECKLE TISSUE CIRCULATION ANALYZER

The effects of topical adrenergic agents on the tissue circulation of the optic nerve head (ONH) were studied in animal and human eyes with use of a laser speckle tissue circulation analyzer. Drugs studied were nipradilol, a beta(1-2)-blocker with weak alpha-blocking and nitrogly cerinlike activities: bunazosin. a selective alpha(1)-blocker; carteol ol, a beta(1-2)-blocker with intrinsic sympathomimetic activity; and b etaxolol, a selective beta(1)-blocker. In the animal experiment, one e ve each of nine albino rabbits received 0.25% nipradilol (N = 9) twice daily for 15 days or 0.01% bunazosin (N = 10) twice daily for 20 days : the fellow eye received the vehicle of each drug in a randomized mas ked design. Normalized blur (NB) in an area of ONH free of visible sur face vessels, a quantitative index of peripheral blood velocity in ONH , was measured under general anesthesia before treatment and 2 hours a fter the last instillation on the 15th or 20th day. At 15 days, intrao cular pressure and NE in the nipradilol-treated eyes decreased by 4.3 mm Hg (P < 0.01) and increased by 15.9% (P < 0.01), respectively, whil e those in the vehicle-treated eyes showed little change. At 20 days N E in both bunazosin- and vehicle-treated eyes showed little change, wh ile intraocular pressure decreased only in the bunazosin-treated el cs (P < 0.01). In the human volunteer experiment NB was averaged over fi ve pulse:, (mean NE) in both eyes before and 1.5, 3.0 and 4.5 hours af ter a 30 mu L instillation of the vehicle of carteolol or betaxolol to serve as a control. Intraocular pressure, blood pressure and pulse ra te were also, measured. One week later a 30 mu L drop of 2.0% carteolo l (N = 6) or 0.5% betaxolol (N = 10) was instilled in one randomly cho sen eye and the vehicle for each drug in the other eye, and those para meters were measured as above in a double-masked manner. In the carteo lol experiment, mean NE in both eyes was significantly higher at 3 hou rs than it was in the control experiment (P < 0.05), while intraocular pressure was significantly lower in both eyes and blood pressure and pulse rate shelved little change. In the betaxolol experiment, intraoc ular pressure at 1.5 hours and blood pressure at 4.5 hours were signif icantly lower than those in the control experiment (P < 0.05), while m ean NE and pulse rate showed little change. In summary., using the las er-speckle method we found that topical nipradilol and carteolol incre ase ONH blood velocity in rab bits and humans, respectively. This find ing suggests that some topical beta-blockers used clinically ma) influ ence the ONH tissue circulation in patients and that this method may b e used in clinical situations tc, assess the effect of various drugs o n ONH circulation. (C) 1997 by Elsevier Science Inc. All rights reserv ed.