Structural and functional characteristics of meibomian glands in meibomian gland dysfunction
Aim: The thesis aims were to develop techniques to investigate novel aspects of meibomian gland (MG) morphology; to evaluate meibum composition and ocular surface signs and symptoms associated with morphological changes in the glands before and after treatment for Meibomian gland dysfunction (MGD). Methods: There were five method development studies and one clinical trial. The first two studies analysed retrospective meibography images to explore associations between MG morphology with ocular symptoms and signs among symptomatic contact lens wearers and participants with dry eye disease (DED). The third prospective study used multimodal imaging to evaluate MG orifices and explore their associations with, and ability to predict symptoms. The fourth study investigated inter-day and intersubject variations in meibum lipid and protein profile, and the fifth study investigated differences in meibum composition associated with differences in MG structure. Finally, a prospective, randomised, double-masked clinical trial explored alterations in MG structure, function and comfort following Intense Pulsed Light (IPL) therapy. Results: Morphological features of the MGs such as width and intergland distance at the lid margin and Non-Invasive Keratograph Tear Break-up Time (NIKBUT) can predict 68% of the variance in symptoms (Contact Lens Dry Eye Questionnaire-8) in contact lenses wearers. Similarly, width and intergland distance at the lid margin, NIKBUT and MG secretion score could predict 47% of the variance in dryness symptoms (visual analogue scale) in DED. Imaging MG ducts and orifices is feasible with Optical Coherence Tomography (OCT) in-vivo and comparable to measurements made with ex-vivo histology. These novel imaging features along with NIKBUT predicted 41% of the variance in symptoms (Ocular Surface Disease Index) in those with and without MG loss. There were no significant day-to-day variations in meibum lipid and protein profile, but compositional differences between short and long MGs were identified. IPL therapy has a significant impact on certain features of MGs and meibum lipid and protein profiles. Conclusion: Features of the MGs, particularly at the lid margin, can predict symptomatology in contact lens wearers and those with MGD. Multimodal imaging techniques were effective for evaluating MG morphology and sensitive to measuring change following treatment, which may be important for developing targeted therapies to manage MGD and CLD in the future.
meibomian glands, meibum, meibography, meibomian gland dysfunction, anzsrc-for: 3212 Ophthalmology and optometry
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