Abstract
Purpose: :
To evaluate a new hydrogel ring for delivering drugs to the posterior segments of the eye.
Methods: :
A Scleral-ring (external diameter 20 mm, internal diameter 13 mm), and a Corneal-lens (diameter 13 mm) were made from poly(hydroxyethyl methacrylate) hydrogel. Both devices were immersed in 0.3% ofloxacin solution in order to contain the drugs homogeneously. The medicated Scleral-ring was placed on the surface of the sclera of the Japanese albino rabbit. The Corneal-lens, on the other hand, was placed on the surface of the cornea. After 1-8 hours, the rabbits were sacrificed, and then the eye tissues (the aqueous humor and retina/choroid) were removed from the rabbits. The ofloxacin concentrations in the tissues were measured by a high-performance liquid chromatography. The experimental time courses of the drug concentration in the tissues were compared with the ones simulated by using a pharmacokinetic model of ocular drug delivery based on the diffusion/partition model.
Results: :
The Scleral-ring provided the retina/choroid concentration higher than the Corneal-lens over 8 hour. Although the total concentration of the retina/choroid was gradually decreased through 2-8 hours, the posterior concentration was maintained almost constantly for 8 hours. This result suggests that the Scleral-ring is effective for the drug delivery to the posterior segment of the eye. The experimental elimination profiles of ofloxacin in the aqueous humor and retina/choroid were agreed with the simulated profiles. The simulated result clearly indicated that the Scleral-ring could deliver the retina concentration, higher than the Corneal-lens.
Conclusions: :
A ring drug delivery system, such a Scleral-ring, can effectively deliver the drug molecules to the posterior segment of the eye compared with conventional medicated contact lens. The ring drug delivery system would be useful for drug therapy in the posterior segment of the eye.
Keywords: sclera • retina • contact lens