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The retina in cystic fibrosis

Hiscox, Rachel Joy 2013. The retina in cystic fibrosis. PhD Thesis, Cardiff University.
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Cystic fibrosis (CF) is caused by defective function of CF Transmembrane Conductance Regulator (CFTR), an epithelial ion channel that facilitates chloride secretion. Previous research has identified impaired dark adaptation (DA) in CF, which has been attributed to concomitant vitamin A deficiency or CF-related diabetes (CFRD). However, CFTR has been localised to the retinal pigment epithelium (RPE) and it is proposed that abnormal DA could be a primary manifestation of CF. DA is similarly impaired in individuals with type 1 and 2 diabetes and is thought to be caused by retinal hypoxia as oxygen inhalation ameliorates abnormal thresholds. The aim of this thesis was to investigate DA during oxygen inhalation in CF subjects with and without CFRD to gain further insight about the aetiology of this abnormal DA. The work also aimed to examine retinal structure using optical coherence tomography (OCT) to determine the consequences of CFTR dysfunction at the RPE. Final DA thresholds were not impaired in CF subjects as a whole during the inhalation of air. However, when grouped according to diabetic status, CFRD subjects showed a significantly elevated final rod threshold which was ameliorated following oxygen inhalation. This suggests that the retina is hypoxic in CFRD subjects and that impaired DA in CF is secondary to CFRD rather than a primary manifestation of CFTR malfunction at the RPE. Contrary to the proposed hypothesis, retinal and RPE/photoreceptor layer thickness was significantly thinner in CF subjects. These results suggest that impaired CFTR function at the RPE does not directly affect retinal structure. · In conclusion, this is the first study to determine that retinal structural and functional abnormalities are not caused directly by CFTR dysfunction but are a secondary manifestation of the disease. Further research is necessary to understand the impact of these findings.

Item Type: Thesis (PhD)
Status: Unpublished
Schools: Optometry and Vision Sciences
Subjects: R Medicine > RE Ophthalmology
Uncontrolled Keywords: Retina, CFTR, Cystic fibrosis, Dark adaptation
Date of First Compliant Deposit: 30 March 2016
Last Modified: 26 Oct 2017 11:09

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