Keratoconus in Down syndrome: Prevalence, assessment, visual disability, quality of life and corneal cross linking

Abstract

This thesis comprises seven interrelated investigations to better understand visual impairment, corneal features, and keratoconus in people with Down syndrome (DS) in New Zealand-Aotearoa. A review of corneal topographies identified that approximately 1 in 3 athletes with DS who underwent corneal topographic screening at a national sporting event had keratoconus. This study revealed the feasibility of integrating corneal evaluation into community events to improve access to care for a population at risk of keratoconus development. A prospective study using detailed, three-dimensional imaging of the cornea confirmed that keratoconus disproportionately affected this population. This study involved comparison of an extensive range of corneal tomographic parameters for people with DS and keratoconus, suspect keratoconus as well as those without keratoconus. This study also highlighted that eye rubbing disproportionately affected people with DS and keratoconus. Additionally, corneal hydrops, an advanced stage of keratoconus disproportionately affected people with DS compared to the general population. Furthermore, analysis of the impact of keratoconus on vision related quality of life identified that people with DS and keratoconus scored significantly lower in the domains of general vision, near activities, mental health and dependency compared to those with DS who did not have keratoconus. The repeatability of corneal tomography was analysed for this population. This study highlighted that key parameters such as maximum keratometry and minimum pachymetry were notably variable. This indicated the importance of taking several scans during the imaging process. It also uncovered the challenge of monitoring serial scans in this population, as progression or stability may be masked by variability. Further studies revealed that additional investigations are still required into the utility of epithelial thickness distribution and ocular biomechanics for keratoconus detection in DS. A retrospective review of clinical records in a public hospital ophthalmology service highlighted that more severe forms of keratoconus presented more commonly and that regular clinic-based tomography screening is required for this population to prevent severe stages. Ultimately these studies informed the development of a proposed guideline for the care of keratoconus in people with DS such that early detection and management can be undertaken to minimise visual impairment.