Timolol Maleate and Choroidal Blood Flow
We have measured choroidal blood flow in cats by determining the rate of clearance of indocyanine green dye from the choroidal circulation. Measurements were made by rapidly (0.2 s) injecting indocyanine green dye (2.5 mg/ml), in 0.1 ml increments, into the common carotid artery and photoelectrically monitoring its concentration in the superior anterior ciliary vein. In the six normal cats studied, the choroidal blood flow during the control periods averaged 13.9 ± 2.7 ml/min/ml of choriocapillaris (mean ± S.E.) while in the five low flow cats it averaged 4.6 ± 0.6 ml/min/ml of choriocapillaris. Following a timolol maleate injection of 10 mg into the common carotid artery, the systemic blood pressure usually decreased and then returned essentially to control level within 5 to 20 minutes. The choroidal blood flow tended to parallel the systemic blood pressure but usually fell less. In the low flow cats, the blood flow increased briefly above control levels even when the blood pressure was below control. We conclude that timolol maleate does not constrict choroidal vessels in the cat.
KeywordsIntraocular Pressure Common Carotid Artery Perfusion Pressure Indocyanine Green Systemic Blood Pressure
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