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This dissertation, The Characterization of Retinal Nerve Fiber Layer Thickness in Normal, High-tension and Normal-tension Glaucoma Using Optical Coherence Tomography by Kwok-hei, Mok, 莫國熙, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of thesis entitled The characterization of retinal nerve fiber layer thickness in normal, high- tension and normal- tension glaucoma using Optical Coherence Tomography. Submitted by Kwok Hei MOK for the degree of Doctor of Philosophy at The University of Hong Kong in May 2005 Glaucoma is a complex multifactor disorder known to cause progressive loss of retinal ganglion cells and their axons, leading to a reduction in the thickness of the Retinal Nerve Fiber Layer (RNFL). There remains considerable disagreement within the glaucoma community as to the possible morphologic damage pattern differences in the primary chronic open angle glaucoma patients with elevated intra-ocular pressure (HTG) and those with normal intra-ocular pressure (NTG). It would be intriguing to determine if there is any morphological difference in RNFL between HTG and NTG patients since this may provide clues as to possible different factors responsible for the damage to their eyes. iiOptical coherence tomography (OCT, Humphrey systems Inc., Dublin, CA, USA) is a noninvasive technology that allows high resolution (approximately 10μm) in vivo cross-sectional imaging of the retinal structures based on the principle of Michelson interferometry. It allows a direct and objective estimation of RNFL thickness. One major benefit of RNFL assessment using OCT is that twelve clock hour thickness values along a circular path around the optic disc are displayed. This regional data analysis makes it more sensitive to detect localized changes. However, reproducibility of regional data was reported to be unsatisfactory. We found that increasing the number of scans to five scans per examination significantly improves reproducibility of regional values in both healthy and glaucomatous eyes. The peri-papillary RNFL under investigation exhibited double-hump patterns. RNFL was thickest in the supero- and infero-temporal regions (double humps) and thinnest in the temporal and nasal regions (double troughs). We observed that the RNFL in 129 eyes of 129 Hong Kong-Chinese subjects appeared to significantly decrease both over time cross-sectionally (3.3μm per decade, pTo best of my knowledge, there has been no study specifically investigating the profile of RNFL injury at different stages of glaucoma. Specific glaucomatous RNFL profiles injury may not only serve as a useful basis for diagnosing and monitoring disease progression, but also provide insights into the mechanism and pattern of ganglion cell atrophy in glaucomatous optic neuropathy. Glaucomatous RNFL loss occurs with regional preferences at different stages of the disease. We first reported that only infero-and supero-temporal regional values were found to decrease continuously, and that a localized defect was observed first in the infero-temporal region in pre-perimetric and early stages. This finding of preferential damage in the inferior as opposed to superior fibers in the very early stage of glaucoma damage is intriguing, and may shed light into the mechanism of the damage.. In NTG and HTG patients, our findings showed that RNFL topographical changes are similar i

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