Primary Angle Closure Glaucoma (PACG) is a worldwide leading cause of irreversible blindness much more prevalent in Asia than in European-derived populations. Patterns of ethnic differences may account for prevalence variation of the disease. Recent papers have reported a predicted rise in European-derived populations. Ocular risks associated with PAC(G) include an axially small, hypermetropic eye with a large lens. Potentially, there are patients in the UK with 'at risk' ocular biometrics predisposing them to PAC(G). Biometric disparities between ethnicities infer morphological variation of PAC(G).The morphology of PAC(G) can be evaluated using ultrasound biomicroscopy (UBM) and the development of a novel linear probe has enhanced its clinical utility. UBM allows quantitative analysis of the anterior chamber, however, there are inherent difficulties in identifying the landmark scleral spur. Qualitative image analyses are urgently required to assess the morphology of closure. Clinical grading scales (CGS) have been successful in other areas within ophthalmology; their application to PAC(G) is investigated within this thesis. The specific aims of the thesis are to: a) examine biometric differences between Caucasian & Chinese patients with PAC(G); b) describe the development of a series of CGS for PAC(G) and c) validate the CGS.Biometric differences between Chinese and Caucasian sample populations exist. The Caucasian cohort exhibit typical biometric findings associated with PAC(G): significantly smaller eyes, shallower anterior chambers, larger lenses, and a significantly shorter vitreous depth, when compared to Chinese counterparts. Biometric differences lend support to variation of PAC(G) mechanisms between ethnicities. A series of clinical CGS were developed using a 'consensus' based approach. The results: utilize psychometric techniques to evaluate inter-observer error; analyse intra-observer agreement by visualising concordance; target pruning to eliminate inter-observer confusion when constructing the CGS. A new custom-made software was developed to evaluate the performance of the CGS. The results show good intra- and inter- observer repeatability to characterise the morphology of closure. This is the first study describing a comprehensive method to construct and validate CGS in PAC(G). These can be used to evaluate the morphology of closure and in the future assess the fidelity of PAC(G) management.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:713545 |
| Date | January 2015 |
| Creators | Siddiqi, Rizwana |
| Publisher | University of Manchester |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | https://www.research.manchester.ac.uk/portal/en/theses/anterior-segment-morphology-in-angle-closure(75cd5598-a53c-4f04-b67b-37130210bbdc).html |
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