Abstract

Silicone Hydrogel (SiHy) contact lenses are highly successful compared to previous soft lenses; they were developed to provide superior oxygen permeability. However, the hydrophobic natures of the silicone segments enhance lipid sorption which may diminish the lens surface wettability, clarity and comfort. While lens and lens care product are designed to remove lipid deposition, there is lack of experimental evidence to evaluate the actual performances with respect to lipid removal. An in vitro model using an artificial tear fluid containing radiolabeled lipids was employed in this thesis research to evaluate the efficacy of different multi-purpose lens care solutions in removing lipids from SiHy contact lenses. Additional rubbing with the lens care solution is often encouraged by professionals. Part of this research evaluated the effect of additional rubbing process on lipid removal. Overall, a multi-purpose solution (MPS) for lens care, Opti-Free PureMoistÂ®, removed the most lipid deposition from lenses (senofilcon A, comfilcon A, and balafilcon A and one conventional hydrogel lens polymacon). The overall removal percentages were approximately 55% of DPPC and 28% of cholesterol from a conventional hydrogel. However, the MPSs did not remove lipids effectively from SiHy lenses. The highest percentages of removal were 3.08% of DPPC and 0.76% of cholesterol from SiHy lotrafilcon B lenses with Opti-Free PureMoist. The rubbing process increased the amount of removal in some MPSs, but the effects were small. The lack of removal of lipid suggests that the surfactants in the MPSs are not hydrophobic enough to remove lipids from SiHy lenses. Apparently a majority of deposited lipids absorbed into the lens matrix as rubbing did not enhance removal significantly. Future study on determining the concentration profile of lipid sorption throughout the lens thickness is encouraged. Another topic in this research thesis is the use of hydrogel lenses to deliver comfort agents or lubricating molecules from lenses. A screening study was performed in this research to select possible agents to be loaded into several SiHy macromer formulations. Experiments showed that comfort agents PNVP and Kollidon were the best candidates for such a procedure.

Degree

College and Department

Ira A. Fulton College of Engineering and Technology; Chemical Engineering

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