PURPOSE: The purpose of this study was to develop an advanced in vitro blink model that can be used to examine the release of a wide variety of components (for example, topical ophthalmic drugs, comfort-inducing agents) from soft contact lenses .
METHODS: The model was designed using computer-aided design software and printed using a stereolithography 3D printer . The eyelid and eyeball were synthesized from polyvinyl alcohol and silicone material, respectively . Simulated tear fluid was infused through tubing attached to the eyelid using a syringe pump . With each blink cycle, the eyelid slides and flexes across the eyeball to create an artificial tear film layer . The flow-through fluid was collected using a specialized trough . Two contact lenses, etafilcon A and senofilcon A, were incubated in 2 mL of a water-soluble red dye for 24 h and then placed on the eye model (n = 3). The release of the dye was measured over 24 h using a tear flow rate of 5 µL/min .
RESULTS: Approximately 25% of the fluid that flowed over the eye model was lost due to evaporation, nonspecific absorption, and residual dead volume . Senofilcon A absorbed more dye (47.6 ± 2.7 µL) than etafilcon A (22.3 ± 2.0 µL). For etafilcon A, the release of the dye followed a burst-plateau profile in the vial but was sustained in the eye model . For senofilcon A, the release of the dye was sustained in both the vial and the eye model, though more dye was released in the vial (p <0.05). Overall, the release of the dye from the contact lenses was higher in the vial compared with the eye model (p <0.05).
CONCLUSION: The blink model developed in this study could be used to measure the release of topical ophthalmic drugs or comfort agents from contact lenses . Simulation of a blink mechanism, an artificial tear film, and nonspecific absorption in an eye model may provide better results than a simple, static vial incubation model.
Index: contact lenses, drug delivery, eye model, in vitro