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Keratoconus in Down’s syndrome

Campbell, Stephanie 2017. Keratoconus in Down’s syndrome. PhD Thesis, Cardiff University.
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Abstract

Keratoconus is a primary cause of visual impairment in young people in the UK. Corneal cross-linking is a recently-introduced treatment for halting progression of keratoconus, which is more effective in early cases. It has long been observed that keratoconus is significantly more prevalent in those with Down’s syndrome (DS) when compared to the general population. Moreover, young people with Down’s syndrome are less able to report early symptoms of keratoconus, often presenting late to eye clinics when cross-linking is no longer possible. A cohort of children and young people with DS were examined with the aim of discovering optometric correlates of keratoconus and to establish the utility of these parameters as risk factors for identifying keratoconus in primary care. An abnormal retinoscopy reflex was found to be the earliest indicator of keratoconus, showing greater potential as a screening test than either refractive error or objective vision measurement. The cornea of individuals with DS is known to be thinner and steeper than usual. Despite this, the high prevalence of keratoconus in DS has long been attributed to eye-rubbing, despite the inherent difference in baseline shape. The current work revealed no relationship between eye rubbing and the development of keratoconus in DS eyes. In vivo biomechanical analysis demonstrated an increased deformation tendency in DS eyes vs. controls, largely accounted for by the decreased corneal thickness in the test group. These results suggest that the high prevalence of keratoconus in DS originates from biomechanical weakness, permitting the loss of regular corneal shape in the absence of eye rubbing. However, ultrastructural analysis of the cornea of the Tc1 mouse model of DS revealed an unaltered collagen and proteoglycan structure. Topographical examination of ‘cone’ morphology in individuals with and without DS demonstrated a similar phenotype at all stages of the disorder, indicating that people with DS and keratoconus may be a useful cohort for future genetic studies into keratoconus as a whole.

Item Type: Thesis (PhD)
Status: Unpublished
Schools: Optometry and Vision Sciences
Subjects: R Medicine > RE Ophthalmology
Uncontrolled Keywords: Keratoconus, Down’s syndrome, Downs syndrome, Down syndrome, Trisomy 21, cornea
Date of First Compliant Deposit: 4 April 2017
Last Modified: 04 Jun 2017 09:46
URI: http://orca.cf.ac.uk/id/eprint/99603

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