Measurement of aqueous flow in rabbits with corneal and vitreous depots of fluorescent dye.

Using pigmented rabbits, two fluorophotometric methods for measuring aqueous flow were compared. A corneal depot of dye was used to measure aqueous flow in one eye of each rabbit while the vitreous depot method of Johnson and Maurice was used to measure aqueous flow over the same period in the fellow eye. After intravenous administration of acetazolamide or mannitol, during the first hour after drug delivery a decrease in aqueous flow was observed in the eye with the corneal depot of dye that was undetected in the eye with the vitreous depot of dye. In rabbits which were water-loaded by orogastric tube, an increase in aqueous flow was observed by the corneal depot method, while the vitreous depot method indicated a decrease in aqueous flow. The vitreous depot method depends on the assumption that the rate of loss of dye from the vitreous remains stable. It is shown that movement of water into or out of the vitreous can cause large changes in the rate of movement of dye from the vitreous to the anterior chamber and can make interpretation of the vitreous method ambiguous. While the vitreous depot method is probably superior for measuring sustained changes of the rate of aqueous flow over tens of hours or days, it is concluded that it cannot be used for measuring changes over shorter periods.