The nature and fate of ocular lipids in contact lens wear

Abstract

The main objectives of this project were to adapt existing analytical techniques, for the examination of lipids extracted from subject-worn contact lenses and tear samples. A great amount of research has been done in the area of meibomian gland lipid analysis; however, there has been little research investigating ex vivo lens deposits and more importantly the effect of lens wear on the lipid layer. Since the development of silicone hydrogel contact lenses, lipid deposition and problems that relate to lipid deposition have increased. Discontinuation of lens wear is often related to discomfort, particularly symptoms of dryness.This research was therefore based on the analysis of changes in lipidstructure as a result of contact lens wear. The development of an array of techniques enabled different aspects of lipid structure to be examined Chromatographic techniques such as thin layer chromatography (TLC), high performance liquid chromatography (HPLC) and gas chromatography (GC) were utilised to separate individual lipid species and provide structural information. GC analysis of ex vivo lens extracts showed significant differences in lipid profiles between daily wear and continuous wear lens extracts. As well as assessment of lipid conformational changes, the presence of lipid oxidative products in the ocular environment were investigated. Malondialdehyde (MDA), a secondary lipid oxidative end product has previously been linked with contact lens intolerance and discomfort. This research showed that oxidative products were building-up within the contact lens matrix.