Effect of long-term topical betaxolol on tissue circulation in the iris and optic nerve head.
The effect of long-term topical betaxolol on tissue circulation in the iris and optic nerve head was studied. Twenty microliters of 0.5% betaxolol ophthalmic solution was instilled in one eye of an albino rabbit and the same amount of physiological saline in the fellow eye twice daily for 20 days. A quantitative index of tissue blood velocity, NB value, was measured in the iris (21 rabbits) and optic nerve head (31 rabbits) of both eyes before the first instillation and 2 hr after completion of instillations, using a laser speckle tissue circulation analyser of which details have been reported previously. The intraocular pressure was also measured at 5-day intervals. The intraocular pressure was lowered by 2-3 mmHg only in the betaxolol-treated eye (P < 0.01). Both in the iris and optic nerve head no significant bilateral difference in the NB was seen before the first instillation, while it was significantly greater in the betaxolol-treated than in the contralateral control eye by about 10% after completion of instillations (P < 0.02-0.05). The difference between the NB after completion of instillations and that before the first instillation was significantly greater in the betaxolol-treated eye than in the contralateral control eye both in the iris and optic nerve head (P < 0.001-0.02). Twenty-day twice daily instillation of 0.5% betaxolol caused relatively small, but significant increase in tissue blood velocity in the ipsilateral iris and optic nerve head in albino rabbits, which may have clinical implications.
Araie
M
M
Department of Ophthalmology, University of Tokyo School of Medicine, Japan.
Muta
K
K
D000287:Administration, Topical; D000319:Adrenergic beta-Antagonists / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D015784:Betaxolol / Q000008:administration & dosage / Q000494:pharmacology*; D001783:Blood Flow Velocity / Q000187:drug effects; D001794:Blood Pressure / Q000187:drug effects; D002121:Calcium Channel Blockers / Q000494:pharmacology; D007429:Intraocular Pressure / Q000187:drug effects; D007498:Iris / Q000098:blood supply / Q000187:drug effects*; D009543:Nifedipine / Q000031:analogs & derivatives / Q000494:pharmacology; D009898:Optic Disk / Q000098:blood supply / Q000187:drug effects*; D011817:Rabbits
D000319:Adrenergic beta-Antagonists; D002121:Calcium Channel Blockers; C035100:nilvadipine; D009543:Nifedipine; D015784:Betaxolol