Effect of brimonidine on optic nerve blood flow in rabbit Original Reearch Article

PURPOE: Brimonidine i a highly elective α2-adrenoreceptor agonit that lower intraocular preure. The aim of the preent tudy wa to analyze in vivo the vaomotor effect and the influence of brimonidine on blood flow within the optic nerve, by mean of intraluminal microvacular corroion cating technique and intravacular injection of colored microphere. METHOD: New Zealand white rabbit received either brimonidine tartrate 0.2% or placebo (vehicle) topical drop in one eye for 4 week. Intraocular preure were meaured at baeline and 4 week. The anterior optic nerve microvaculature of four rabbit wa examined with corroion cating for region of focal vaocontriction. Optic nerve blood flow wa determined in 16 rabbit by mean of nonradioactive colored microphere. REULT: The vaocontriction value of the hort poterior ciliary arterial branche in the brimonidine eye were 16.7% ± 3.7%. In the fellow untreated eye, the mean vaocontriction wa 16.6% ± 2.4%. In the placebo-treated eye, the average contriction wa 15.9% ± 3.2%; the fellow eye howed a mean contriction value of 16.1% ± 5.3%. There wa no tatitical difference between any of the group (P= .2). The optic nerve blood flow in the brimonidine-treated rabbit wa 0.18 ± 0.06 ml/mg/min and 0.17 ± 0.04 ml/mg/min in the treated and the fellow eye, repectively. The difference between the optic nerve blood flow in the brimonidine-treated eye and the optic nerve blood flow in all of the untreated eye (0.19 ± 0.06 ml/mg/min) alo wa not tatitically different (P = .82). CONCLUION: Long-term application of brimonidine 0.2% doe not affect the blood flow or vaomotor activity of the anterior optic nerve.