Investigation of the effect of meibomian gland health and delivery of lipids on signs and symptoms of contact lens discomfort

Globally, approximately 150 million people wear contact lenses and nearly half report discomfort during lens wear. A significant portion eventually discontinue use. Contact lens discomfort (CLD) is a multifactorial condition, with meibomian gland dysfunction (MGD) playing a major contributory role. The meibomian glands secrete lipids such as (O-acyl)- ω- hydroxy fatty acids (OAHFA), wax esters, and cholesteryl esters which maintain tear film stability and reduce evaporation. Alterations to these glands can lead to increased tear evaporation, ocular surface dryness, and ocular discomfort. The aim of this thesis was to evaluate the qualitative and quantitative changes in symptoms of MGD and CLD after Intense Pulsed Light (IPL) therapy, and during wear of lipid-loaded contact lenses. In the first phase, a randomised, double-masked clinical study evaluated IPL therapy in symptomatic contact lens wearers and assessed both clinical outcomes and eyelid microbiota within the same cohort. Two IPL sessions with meibomian gland expression significantly improved Contact Lens Dry Questionnaire (CLDEQ-8) scores, and meibomian gland function by day 42, though effects diminished by day 90. Concurrently, eyelid margin swabs revealed a marked reduction in gram-positive cocci and rods, particularly coagulase-negative staphylococci and Bacillus spp., at day 42, indicating IPL’s transient antimicrobial effect. Bacterial regrowth by day 90 mirrored the decline in symptomatic relief, suggesting, short-duration therapeutic window. To optimize treatment outcomes, a comprehensive review of existing IPL studies in MGD was conducted. The review identified that the M22 device, when used to deliver 5-12 pulses across two passes in three treatment sessions, produced the most sustained improvements in meibum quality, tear break up time and symptom relief lasting up to 90 days in MGD. The second phase of thesis evaluated contact lenses embedded with OAHFA nanoparticles stabilized with surfactants, The lenses formed with Pluronic F127 improved both tear film stability and subjective comfort after 8 hours of lens wear, but the nanoparticles lacked long-term stability. Therefore, an alternative, surfactant tocopherol polyethylene glycol succinate (TPGS) was used to obtain nanoparticles. Whilst these TPGS nanoparticles were much more stable, lenses soaked in these containing OAHFAs, or Wax esters showed no significant improvement in tear film stability and subjective comfort. Experimental analysis revealed that TPGS-induced lens warpage and diameter changes, which likely interfered with lens performance. In conclusion, IPL therapy showed potential as a non-pharmacological option for improving symptoms and meibomian gland function in symptomatic contact lens wearers, but future studies on frequency of its application to give sustained effects are needed. Lipid loaded lenses also demonstrate promise, but further research is needed to obtain stable nanoparticles that do not affect lens parameters. These findings offer new insights into multimodal approaches to manage CLD and highlight the importance of formulation and treatment protocol optimization in future clinical applications.