J. H. Kim, T. W. Kim and D. M. Kim

Purpose: To investigate the effect of topical betaxolol on impaired choroidal blood flow induced by endothelin-1 (ET-1) injection into the vitreous of albino rabbits.

Methods: Betaxolol (betaxolol group, n = 7) or balanced salt solution (control group, n = 6) was instilled in the right eyes of albino rabbits 2 hours before and 12 hours after intravitreal injection of ET-1 (10^-6 M, 10 m l). Blood pressure, intraocular pressure and choroidal blood flow were measured prior to the instillation of betaxolol or balanced salt solution. These measurements were also taken immediately before, 2 hours, 12 hours, and 24 hours after ET-1 injection. Choroidal blood flow was measured with scanning laser Doppler flowmeter (Heidelberg Retina Flowmeter v3.23, Heidelberg Engineering, Heidelberg, Germany).

Results: Intravitreal injection of ET-1 decreased choroidal blood flow. Compared to the control group, topical administration of betaxolol significantly inhibited the decrease of blood flow at 2 hours (betaxolol group = 45.9 ± 11.7% decrease, control group = 59.7 ± 8.8% decease, p = .022), 12 hours (betaxolol group = 38.1 ± 17.6% decease, control group = 55.6 ± 6.6% decrease, p = .046), and 24 hours (betaxolol group = 21.0 ± 21.8% decrease, control group = 47.6 ± 9.1% decrease, p = .015) after ET-1 injection. There were no statistically significant differences in the change of either systemic blood pressure or intraocular pressure between the two groups.

Conclusion: The decrease in choroidal blood flow after intravitreal injection of ET-1 was partially inhibited by topical betaxolol.