Characterization of hydrogel contact lens materials and their interaction with tear film proteins
- The human tear film is a thin fluid film that coats the corneal epithelium of the eye, protecting it bacteria and debris. Maintaining a stable tear film is important for ocular health and comfort; issues associated with tear film stability and ocular surface health can result in feelings of dry eye and discomfort. These symptoms are especially common in patients using contact lenses and are the primary cause for contact lens dropout. To better understand some of the factors that may govern contact lens discomfort, this dissertation focuses on fundamental properties of contact lens hydrogel materials, the human tear film, and the interface between the tear film and contact lenses. Firstly, we wanted to better understand the complex chemistries present in various contact lens materials and we developed methods using solid-state NMR to do so. Using this method, we were able to estimate the molecular contributions of major lens components and were also able to estimate the uptake of a tear film protein, lysozyme, within contact lenses in an in vitro setting. The technique ultimately allowed us to demonstrate that a benzotriazole-based UV-blocker found within commercial contact lens materials also functions as an antioxidant and protects protein deposits from oxidation. The second half of this dissertation focuses on tear film stability, which we first studied in the presence of contact lenses. We investigated the effect of protein deposition on contact lenses on the stability of the tear film to understand if discomfort associated with protein deposition could be attributed to a physical instability in the tear film. Protein deposition was found to increase the surface wettability of contact lenses; however, contact lens surface wettability in saline was uncorrelated with fluid film stability in an artificial tear solution due to the interfacial fluid properties of the artificial tear film. Instead, evaporation from contact lenses was a better indication of the tear film stability in this in vitro setting. Finally, because some contact lens discomfort arises from inherent deficiencies in a patient's tear film, we also focused our efforts on the contribution of the mucin layer to tear film stability in the absence of contact lens materials. We found that mucins help contribute to tear film stability by altering the van der Waals forces within the film, giving rise to a disjoining pressure; additionally, in the presence of evaporation, there are thermal and solute gradients that cause surface-tension driven flow (Marangoni flow) which also stabilizes the film. Together, this dissertation sheds light on some of the potential contact lens and tear film factors that have been hypothesized to affect contact lens comfort in patients and introduces new methods to study additional physicochemical factors related to the tear film and contact lens materials.
|Type of resource
|electronic resource; remote; computer; online resource
|1 online resource.
|Rabiah, Noelle I
|Fuller, Gerald G
|Fuller, Gerald G
|Swartz, James R
|Degree committee member
|Swartz, James R
|Stanford University, Department of Chemical Engineering.
|Statement of responsibility
|Noelle I. Rabiah.
|Submitted to the Department of Chemical Engineering.
|Thesis Ph.D. Stanford University 2019.
- © 2019 by Noelle I Rabiah
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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