Characterising and Modifying the Keratoconus Disease Process in New Zealand – The Aotearoa Research into Keratoconus (ARK) Project

Abstract

This thesis contains six inter-related investigations aimed at improving the understanding of the epidemiology, clinical characteristics and natural history of keratoconus in New Zealand (NZ) and to investigated the safety and efficacy of two novel high intensity, high irradiance accelerated corneal collagen cross-linking (A-CXL) protocols. The project was titled the Aotearoa*1 Research into Keratoconus (ARK) Project. The ARK Study: Part I investigated the epidemiology and basic clinical characteristics of subjects with keratoconus managed by optometrists in NZ. The results of ARK Part I possibly confirm the long held clinical suspicion that keratoconus has an ethnic predisposition for M ori and Pacific Peoples individuals. Furthermore, the results suggest that keratoconus is potentially more severe among The ARK Studies: Part IIA, B and C, investigated the phenotypic clinical characteristics and natural history of keratoconus in NZ utilising both prospective and retrospective designs. ARK Part IIA, indicated that keratoconus may have a greater inter-eye disease asymmetry in NZ and that corneal tomographic features/disease severity are correlated with corneal microstructure and biomechanical integrity. ARK Part IIB and C suggest that keratoconus may continue to progress beyond age 30 years and ARK Part IIB characterised the relationship between corneal curvature/power and contact lens corrected visual acuity. The ARK Study: Part IIIA focused on the repeatability and comparability of corneal curvature/power and pachymetry in three commonly used corneal tomographers in keratoconic eyes and revealed that; corneal curvature/power was most repeatable on the Pentacam HR while pachymetry was most repeatable on the Galilei G2 and the Orbscan II was least repeatable for all parameters, however all measured parameters cannot be used inter-changeably between the three devices. ARK Part IIIB investigated two novel A-CXL protocols utilising continuous and pulsed high irradiance, high intensity ultraviolet-A irradiation and demonstrated that both are safe and effective at slowing or halting the progression of keratoconus 12-months post-operatively. The results of the inter-related investigations that form the ARK project provide new data on the epidemiology, clinical characteristics and natural history of keratoconus in NZ and the safety and efficacy of two novel A-CXL protocols.