Microfluidic Tool Development for Contact Lens Regulatory Science and Personalized Ophthalmology Open Access
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Understanding the interactions between contact lenses, human tears, and lens care products is essential to ensuring safe contact lens wear. Current contact lens regulatory testing (e.g. cleaning and disinfection) is characterized by low throughput and high cost, requiring full-size contact lenses and artificial tear solutions. In this dissertation work, current testing methods are miniaturized to increase the experimental efficiency of contact lens regulatory research. In the process of miniaturization, working volumes are sufficiently reduced to enable human tear handling with contact lens materials. Personalized contact lens care according to an individual's unique tear chemistry has the potential to translate into improved patient outcomes.A transitional, miniaturized, microplate method was first employed to investigate the effects of fluorescent labels on protein sorption into contact lens hydrogel materials. Fluorophores are commonly used to label proteins in order to visualize and/or quantify protein uptake into contact lens hydrogel materials. However, such labels may alter protein sorption behavior leading to quantitative differences that do not accurately reflect the uptake of protein in their native, unlabeled state. Therefore, a study was conducted to explore the interactions between proteins, labels, and contact lens hydrogel materials on overall protein uptake. Once the effect of such labels was determined, the microplate method was then applied towards the study of contact lens cleaning. Contact lens care solutions known as multipurpose solutions (MPS) contain surfactants to enable the removal of tear film deposits. Surfactants enable the removal of surface-adsorbed soils by reducing the interfacial energies at the surface/water and soil/water interfaces. Classical surfactant theory states that cleaning efficiency increases with increasing surfactant concentration especially at or above the critical micelle concentration (CMC). However, the surfactants found in MPS are not traditional, low molecular weight surfactants but non-ionic, block copolymers. Therefore, the effect of this difference on contact lens protein detergency was investigated.Human tear profiles are known to vary between individuals which can potentially translate to significant differences in contact lens cleaning outcomes between different MPS formulations. One way to optimize the selection of MPS is to incorporate human tear testing. However, human tear volume is too low even for the microplate method to handle in any practical sense. As a result, a microfluidic platform was developed capable of integrating human tears with lens materials and MPS to analyze product cleaning and disinfection performance for personalized ophthalmology.