Abstract

Human tear film is an accessible biospecimen rich with useful biological information. As tear protein biomarkers for both ocular and systemic diseases have been identified in tears, efforts are being made to create point-of-care tests useful for clinical diagnoses. However, there are significant obstacles to tear diagnostics, including inadequate sampling methods and biomarkers with insufficient sensitivity and specificity. Furthermore, tear film diagnostics are particularly challenging for dry eye disease (DED) patients, where low tear volume makes sampling more difficult and the multifactorial nature of DED makes identifying the exact pathological subtype very complex. As soft contact lenses (SCLs) are designed for optimal ocular surface interaction and concentrate proteins on the eye regardless of tear volume, we hypothesized that we could improve tear sampling methods for research and diagnostic purposes. We further hypothesized that we could identify new and existing and DED biomarkers using SCL tear film sampling. To begin, we demonstrate SCL sampling in vitro and then compare SCLs to other current tear sampling methods in vivo. Objectively, we observe that SCLs do not show signs of ocular surface irritation, regardless of previous SCL use. We also see that SCLs sample similar types and amounts of proteins relative to other methods. Subjective assessments of tear sampling methods are also made by subjects. Our results indicate that training and experience in tear sampling are key components which may significantly impact subject experience as well as the tear type collected. Next, we optimized our tear sampling method by comparing different SCLs materials in search of an ideal lens. Our data show that certain combinations of SCL materials and mass spectrometry (MS) sample preparation methods can lead to significant polymer contamination in MS. Furthermore, we observe individual protein binding specificity based on SCL chemistry. Our experiments reveal etafilcon A and verofilcon A lenses as the optimal SCL materials for tear film sampling. Finally, a pilot study in DED candidates using SCL sampling confirms the presence of previously reported biomarkers in DED subjects as well as identifies new biomarkers for future validation studies. We also correlate clinical metrics to biochemical findings and identify correlations between tear film homeostasis and pathologic phenotypes. Ultimately, these studies demonstrate SCL sampling is an advantageous alternative to current tear film sampling methods, useful for biomarker discovery, and potentially, clinical diagnostics.

Degree

PhD

College and Department

Physical and Mathematical Sciences; Chemistry and Biochemistry

Rights

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