M.Sc. (Biochemistry) / Dry eye disease (DED) and keratoconus (KC) continue to affect the quality of life of many South Africans (and elsewhere) and in the case of KC often leads to blindness. It is estimated that DED affects 14% to 33% of the population worldwide, while 1 in 2000 of the worlds population is affected by KC. However, details of the etiology of these diseases and their biochemical ‘fingerprint’ remain uncertain. In this study, emphasis was placed on the investigation of immunological proteins in the precorneal tear film of DED and KC subjects and meibomian lipids in these individuals. Tear fluid and meibum were collected from control, DED and KC volunteers. Control subjects were non-contact lens wearers and free from ocular diseases, whereas DED subjects were diagnosed by means of an ocular surface disease index (OSDI) questionnaire. DED subjects were divided into two groups: ‘moderate DED’ and ‘severe DED’ based on OSDI. KC subjects were diagnosed by the use of a slit-lamp biomicroscopy exam. Enzymelinked immunosorbent assays were performed to quantitate secretory immunoglobulin A (sIgA), tumour necrosis factor-alpha (TNF-á) and matrix metalloproteinase-1 (MMP-1) in the collected tear fluid. Meibum was analysed with proton nuclear magnetic resonance (1H-NMR) spectroscopy and Fourier transform infrared spectroscopy (FTIR). Multivariate data analyses (PCA) were used to extract interpretable information from the multidimensional data generated from the aforementioned techniques and used to build a broad picture of the general lipidomic differences between DED, KC and healthy subjects. Tear levels of sIgA and MMP-1 were significantly decreased in patients with KC compared to control. In contrast, the tears of severe DED subjects were characterised by higher levels of TNF-á and lower levels of sIgA. In subjects with moderate DED, TNF-á levels were significantly elevated. The results of this study re-emphasize that KC and DED individuals are associated with differential expression of specific tear proteins and support the view that the severity of DED is reflected in the levels of immunological proteins present in basal tears. Differences in the chemical composition of meibum from subjects with severe DED and KC compared to control were observed, more specifically in the aliphatic region of 1H-NMR spectra and C-C rocking region of FTIR spectra. The results therefore point towards the saturated components of fatty acids (and their chemical environments) as key targets for future investigations to elucidate compositional differences between DED, KC and healthy meibum.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:uj/uj:11669 |
| Date | January 2014 |
| Creators | Schnetler, Rozanné |
| Source Sets | South African National ETD Portal |
| Detected Language | English |
| Type | Thesis |
| Rights | University of Johannesburg |
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