S. Orgul et al., OPTIC-NERVE VASOMOTOR EFFECTS OF TOPICAL BETA-ADRENERGIC ANTAGONISTS IN RABBITS, American journal of ophthalmology, 120(4), 1995, pp. 441-447
PURPOSE: To examine the anterior optic nerve vasomotor effects of nons
elective and relatively beta 1-selective beta-adrenergic antagonists i
n rabbits, because different influences on optic nerve blood flow with
these medications have been suggested. METHODS: After topical therapy
for 30 days with either timolol maleate 0.5% (six rabbits), betaxolol
hydrochloride 0.5% (six rabbits), or placebo (two rabbits), the micro
vasculature of the optic nerve was examined with an intraluminal micro
vascular corrosion casting technique. The investigators were masked to
both the medication group and the treated eye, The constriction, in p
ercent of the downstream vessel caliber, was measured at the vascular
branching point of arterioles supplying the anterior optic nerve, An a
verage constriction was calculated and compared between the medication
groups and between the treated and the contralateral, untreated eyes.
RESULTS: Constriction values from a total of 218 arterioles supplying
the anterior optic nerve were obtained for the 14 rabbits. The means
of the average constriction on the treated side were comparable betwee
n the groups treated with timolol maleate, betaxolol hydrochloride, an
d placebo (one way analysis of variance, P = .64), as well as between
the treated and untreated eyes (two-tailed t test for paired variables
, P = .68 for timolol maleate and P = .42 for betaxolol hydrochloride)
. The statistical power to find a difference of 5% or more average con
striction was at least 90%. CONCLUSIONS: Both relatively selective and
nonselective beta-adrenergic antagonists produce no observable optic
nerve vasomotor effects in the rabbit eye.