Constant rate infusion for topical ocular delivery in horses: a pilot study.

This study investigates the effectiveness and process of using a continuous infusion pump for delivering topical ophthalmic drugs to the eyes of horses through subpalpebral lavage, using a fluorescein solution as a model.

Objective and Methods

• The study aimed to evaluate how well a continuous infusion pump can be used for delivering topical ophthalmic drugs to the eyes of horses via a technique called subpalpebral lavage.
• Five horses, each with normal eye health, were selected for the study.
• A constant-rate continuous delivery pump was used to administer a 0.01% fluorescein solution into the horses’ eyes via subpalpebral lavage.
• The application of the fluorescein solution was carried out at a rate of 0.14 mL/h over a period of 72 hours.
• At regular intervals, tear samples were collected from the lower part of the conjunctival pocket (ventral conjunctival fornix) with a capillary tube.
• A spectral assay, a type of laboratory test, was then used to measure the concentration of fluorescein in the tear samples.
• Additionally, laboratory studies were performed to assess the procedures used in the study.

Results and Conclusion

• The study resulted in a wide range of fluorescein concentrations in the tear samples collected from the horse’s eyes. The mean concentration of fluorescein in the tear film was around 20% of the applied fluorescein concentration, indicating that a significant dilution occurs during the delivery process.
• However, the dilution varied considerably across individual horses and changed over time. The amount of dilution observed ranged from 0.62% to 60% of the concentration initially applied.
• Issues encountered during the study included the formation of air pockets in the subpalpebral lavage tubing lines. This problem led to a discontinuous application of the fluorescein solution, meaning that the drug delivery was not always constant or uninterrupted.
• In conclusion, the researchers suggest that the constant-rate delivery of ophthalmic medications using a continuous infusion pump might offer a valuable method for delivering topical drugs in horses.
• However, for this method to be effective, the dilution of drugs in the tear film, which reduces the concentration of the drug reaching the eye, must be accounted for. Additional research may be needed to determine how to address this dilution effect effectively.