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University of Pretoria
1.
[No author].
The role of mobile phone web utilisation in creating
economic growth in South Africa
.
Degree: 2010, University of Pretoria
URL: http://upetd.up.ac.za/thesis/available/etd-03232010-123700/ 
► Mobile phone web utilisation is relatively new in South Africa, and not only does it provide more convenience to existing Internet users, but it can…
(more)
▼ Mobile phone web
utilisation is relatively new in
South Africa, and not only does it provide more convenience to
existing Internet users, but it can potentially overcome the access
problems that are attendant in the
utilisation of the web by most
South Africans. This could go a long way to bridging the Digital
Divide and contribute to South Africa’s economic growth. It is
therefore important to understand the role that the South African
mobile phone web
utilisation cluster may play in creating national
competitive advantage. This exploratory research study focuses on
understanding the role of mobile phone web
utilisation in creating
economic growth in South Africa. It uses a combination of empirical
evidence on the mobile phone web
utilisation cluster, academic
theory around Porter’s Diamond Model of the Micro Economics of
Competitiveness, and pre-existing international and local research.
The question that was considered was “Does the Mobile phone web
utilisation cluster represent a source of competitive advantage for
South Africa?” To support this investigation the following areas
were explored; • What is the universe of the mobile phone web
utilisation cluster? • Are the related and supporting industries
conducive to competition? • Are firm strategies, structures and
competitive rivalry conditions conducive to • competitiveness in
this cluster? • Are demand conditions conducive to global and local
competitive growth? • Are factor conditions conducive to
competitiveness? • What is the role of Government? The research
found that in most aspects, this cluster has the potential to play
a role in creating competitive advantage and contributing to South
Africa’s economic growth.
Advisors/Committee Members: Dr P Tobin (advisor).
Subjects/Keywords: UCTD;
Web utilisation
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APA (6th Edition):
author], [. (2010). The role of mobile phone web utilisation in creating
economic growth in South Africa
. (Masters Thesis). University of Pretoria. Retrieved from http://upetd.up.ac.za/thesis/available/etd-03232010-123700/
Chicago Manual of Style (16th Edition):
author], [No. “The role of mobile phone web utilisation in creating
economic growth in South Africa
.” 2010. Masters Thesis, University of Pretoria. Accessed January 19, 2021.
http://upetd.up.ac.za/thesis/available/etd-03232010-123700/.
MLA Handbook (7th Edition):
author], [No. “The role of mobile phone web utilisation in creating
economic growth in South Africa
.” 2010. Web. 19 Jan 2021.
Vancouver:
author] [. The role of mobile phone web utilisation in creating
economic growth in South Africa
. [Internet] [Masters thesis]. University of Pretoria; 2010. [cited 2021 Jan 19].
Available from: http://upetd.up.ac.za/thesis/available/etd-03232010-123700/.
Council of Science Editors:
author] [. The role of mobile phone web utilisation in creating
economic growth in South Africa
. [Masters Thesis]. University of Pretoria; 2010. Available from: http://upetd.up.ac.za/thesis/available/etd-03232010-123700/
University of Pretoria
2.
Elphick, Kate.
The role of
mobile phone web utilisation in creating economic growth in South
Africa.
Degree: Gordon Institute of Business
Science (GIBS), 2010, University of Pretoria
URL: http://hdl.handle.net/2263/23400
► Mobile phone web utilisation is relatively new in South Africa, and not only does it provide more convenience to existing Internet users, but it can…
(more)
▼ Mobile phone web
utilisation is relatively new in South
Africa, and not only does it provide more convenience to existing
Internet users, but it can potentially overcome the access problems
that are attendant in the
utilisation of the web by most South
Africans. This could go a long way to bridging the Digital Divide
and contribute to South Africa’s economic growth. It is therefore
important to understand the role that the South African mobile
phone web
utilisation cluster may play in creating national
competitive advantage. This exploratory research study focuses on
understanding the role of mobile phone web
utilisation in creating
economic growth in South Africa. It uses a combination of empirical
evidence on the mobile phone web
utilisation cluster, academic
theory around Porter’s Diamond Model of the Micro Economics of
Competitiveness, and pre-existing international and local research.
The question that was considered was “Does the Mobile phone web
utilisation cluster represent a source of competitive advantage for
South Africa?” To support this investigation the following areas
were explored; • What is the universe of the mobile phone web
utilisation cluster? • Are the related and supporting industries
conducive to competition? • Are firm strategies, structures and
competitive rivalry conditions conducive to • competitiveness in
this cluster? • Are demand conditions conducive to global and local
competitive growth? • Are factor conditions conducive to
competitiveness? • What is the role of Government? The research
found that in most aspects, this cluster has the potential to play
a role in creating competitive advantage and contributing to South
Africa’s economic growth.
Advisors/Committee Members: Dr P Tobin (advisor).
Subjects/Keywords: UCTD; Web
utilisation
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APA (6th Edition):
Elphick, K. (2010). The role of
mobile phone web utilisation in creating economic growth in South
Africa. (Masters Thesis). University of Pretoria. Retrieved from http://hdl.handle.net/2263/23400
Chicago Manual of Style (16th Edition):
Elphick, Kate. “The role of
mobile phone web utilisation in creating economic growth in South
Africa.” 2010. Masters Thesis, University of Pretoria. Accessed January 19, 2021.
http://hdl.handle.net/2263/23400.
MLA Handbook (7th Edition):
Elphick, Kate. “The role of
mobile phone web utilisation in creating economic growth in South
Africa.” 2010. Web. 19 Jan 2021.
Vancouver:
Elphick K. The role of
mobile phone web utilisation in creating economic growth in South
Africa. [Internet] [Masters thesis]. University of Pretoria; 2010. [cited 2021 Jan 19].
Available from: http://hdl.handle.net/2263/23400.
Council of Science Editors:
Elphick K. The role of
mobile phone web utilisation in creating economic growth in South
Africa. [Masters Thesis]. University of Pretoria; 2010. Available from: http://hdl.handle.net/2263/23400
3.
Jones, Christopher T.
The evaluation and development of a retinal imaging densitometer.
Degree: PhD, 2017, Cardiff University
URL: http://orca.cf.ac.uk/111545/
► The research described in this thesis presents the development and evaluation of a prototype multispectral, imaging densitometer. Ultimately, the aim was to develop a method…
(more)
▼ The research described in this thesis presents the development and evaluation of a prototype multispectral, imaging densitometer. Ultimately, the aim was to develop a method of simultaneously isolating the contributions from the three main photoreceptors, across the retina. Thus, providing the clinician with a viable tool for assessing outer retinal function both efficiently and directly.
The construction and use of the prototype multispectral imaging densitometer was described in detail. Healthy participants were recruited and imaged to evaluate the baseline capability of the device. The results were validated through comparison to published values for optical density, regeneration rates and photopigment distribution as obtained through in vivo, in vitro and in situ techniques. A novel ocular reflection model was developed to characterise and mathematically remove the pre-receptoral stray light from the images.
Whilst the preliminary investigation returned regeneration rates in line with values from the literature, a ‘red shift’ of approximately 30nm was highlighted in the experimental absorption spectra of the visual pigments, hindering their isolation. Investigation into this phenomenon suggested that the cause was pre-receptoral stray light, with both the crystalline lens and the inner retinal layers contributing to the effect. Attempts to remove the crystalline lens component showed a partial reduction of the ‘red shift’. Greater success was achieved through the modelling of the experimental ocular reflection data to simultaneously characterise the contribution from both components.
This research has shown that mapping of visual pigment optical density across the retina is possible with the retinal densitometer described. With further development, the technique is likely to become a useful tool in the diagnosis and monitoring of outer retinal disease.
Subjects/Keywords: RE Ophthalmology
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APA (6th Edition):
Jones, C. T. (2017). The evaluation and development of a retinal imaging densitometer. (Doctoral Dissertation). Cardiff University. Retrieved from http://orca.cf.ac.uk/111545/
Chicago Manual of Style (16th Edition):
Jones, Christopher T. “The evaluation and development of a retinal imaging densitometer.” 2017. Doctoral Dissertation, Cardiff University. Accessed January 19, 2021.
http://orca.cf.ac.uk/111545/.
MLA Handbook (7th Edition):
Jones, Christopher T. “The evaluation and development of a retinal imaging densitometer.” 2017. Web. 19 Jan 2021.
Vancouver:
Jones CT. The evaluation and development of a retinal imaging densitometer. [Internet] [Doctoral dissertation]. Cardiff University; 2017. [cited 2021 Jan 19].
Available from: http://orca.cf.ac.uk/111545/.
Council of Science Editors:
Jones CT. The evaluation and development of a retinal imaging densitometer. [Doctoral Dissertation]. Cardiff University; 2017. Available from: http://orca.cf.ac.uk/111545/
Cardiff University
4.
Feneck, Eleanor Mai.
Three-dimensional studies of the developing mammalian cornea.
Degree: PhD, 2019, Cardiff University
URL: http://orca.cf.ac.uk/128421/
► This thesis aimed to understand the structural changes that occur during the development of the mammalian cornea. The imaging techniques used included novel three-dimensional serial…
(more)
▼ This thesis aimed to understand the structural changes that occur during the development of the mammalian cornea. The imaging techniques used included novel three-dimensional serial block-face scanning electron microscopy, transmission electron microscopy, optical coherence tomography, X-ray diffraction and immunofluorescence. These techniques were utilised to investigate the human, mouse and the fibrillin-1 knockout mouse cornea.
The mouse cornea had no collagenous primary stroma to direct mesenchymal cell migration. Stromal cell projections associated with adjacent corneal stromal cells and the corneal epithelium, and appeared to direct collagen alignment. The mouse stroma expressed types I, II and V collagen, and later type IX collagen in the epithelium. Proteoglycans were observed before collagen deposition in the mouse stroma, associated with stromal cells and collagen fibrils.
A collagenous primary stroma was identified in the human embryonic cornea prior to mesenchymal cell migration. The corneal endothelium contained novel cell extensions that associated with the mesenchymal cells and the acellular collagenous matrix; these results suggested that the endothelium assists mesenchymal cell migration.
The human adult cornea contained true elastic fibres in the peripheral posterior cornea with fibrillin-rich microfibrils in the central posterior cornea. The elastic fibres in the mouse contained only fibrillin-rich microfibrils. In the human, elastic fibres were detected from week 12 of development and had a distribution similar to the mature human cornea. This included elastic fibre
sheets directly anterior to the endothelium and individual elastic fibres in the posterior peripheral stroma.
The fibrillin-1 knockout mouse cornea had reduced stromal thickness and a disorganised extracellular matrix. It is thought that elevated transforming growth factor-beta disrupted the corneal architecture.
This thesis has contributed novel findings of the events that develop the mammalian cornea. The results identified fundamental differences and similarities between the mouse and human models and have suggested new mechanisms in the developmental process.
Subjects/Keywords: RE Ophthalmology
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APA ·
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APA (6th Edition):
Feneck, E. M. (2019). Three-dimensional studies of the developing mammalian cornea. (Doctoral Dissertation). Cardiff University. Retrieved from http://orca.cf.ac.uk/128421/
Chicago Manual of Style (16th Edition):
Feneck, Eleanor Mai. “Three-dimensional studies of the developing mammalian cornea.” 2019. Doctoral Dissertation, Cardiff University. Accessed January 19, 2021.
http://orca.cf.ac.uk/128421/.
MLA Handbook (7th Edition):
Feneck, Eleanor Mai. “Three-dimensional studies of the developing mammalian cornea.” 2019. Web. 19 Jan 2021.
Vancouver:
Feneck EM. Three-dimensional studies of the developing mammalian cornea. [Internet] [Doctoral dissertation]. Cardiff University; 2019. [cited 2021 Jan 19].
Available from: http://orca.cf.ac.uk/128421/.
Council of Science Editors:
Feneck EM. Three-dimensional studies of the developing mammalian cornea. [Doctoral Dissertation]. Cardiff University; 2019. Available from: http://orca.cf.ac.uk/128421/
Cardiff University
5.
Vasalauskaite, Asta.
Visual function in human and experimental glaucoma.
Degree: PhD, 2016, Cardiff University
URL: http://orca.cf.ac.uk/98604/
► Injury to optic nerve (ON) axons plays a major role in glaucoma progression. ON crush is an established model of axonal injury which results in…
(more)
▼ Injury to optic nerve (ON) axons plays a major role in glaucoma progression. ON crush is an established model of axonal injury which results in retrograde degeneration and death of retinal ganglion cells (RGCs). However, it is unknown how signal transmission to higher visual structures such as primary visual cortex (V1) is affected after ON crush. In human glaucoma, visual function is assessed using visual field (VF) tests, but it is also not clear how the test results relate to the disease progression in the retina.
Unilateral ON crush was performed on the left eyes of adult C57BL/6 mice. V1 function of the right hemisphere was assessed longitudinally by optical imaging (OI) and in vivo calcium two-photon imaging under anaesthesia before and at 7 days, 14 days and 30 days after ON crush. Human retinas from glaucoma patients were investigated for changes in RGC density and compared to the score from the VF data obtained prior to the patients’ death.
ISI and 2P experiments demonstrate a significant shift in OD towards the ipsilateral eye and significant reduction of signal magnitude in V1 in response to contralateral eye stimulation in all ON crush animals. Additionally, response magnitude to ipsilateral eye stimulation was significantly increased after ON crush. While there was significant RGC loss in human glaucoma compared to age matched controls that was correlated to mean VF loss, the scores from the individual VF test points were uncorrelated to RGC density in anatomically equivalent areas.
This work demonstrates that unilateral ON crush results in immediate loss of signal transmission from the retina to V1 via a crushed ON. A significant increase of responsiveness in V1 to non-crushed eye stimulation was observed, which indicates that injury of the ON in adulthood may evoke compensatory plasticity in V1.
Subjects/Keywords: RE Ophthalmology
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APA ·
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Manager
APA (6th Edition):
Vasalauskaite, A. (2016). Visual function in human and experimental glaucoma. (Doctoral Dissertation). Cardiff University. Retrieved from http://orca.cf.ac.uk/98604/
Chicago Manual of Style (16th Edition):
Vasalauskaite, Asta. “Visual function in human and experimental glaucoma.” 2016. Doctoral Dissertation, Cardiff University. Accessed January 19, 2021.
http://orca.cf.ac.uk/98604/.
MLA Handbook (7th Edition):
Vasalauskaite, Asta. “Visual function in human and experimental glaucoma.” 2016. Web. 19 Jan 2021.
Vancouver:
Vasalauskaite A. Visual function in human and experimental glaucoma. [Internet] [Doctoral dissertation]. Cardiff University; 2016. [cited 2021 Jan 19].
Available from: http://orca.cf.ac.uk/98604/.
Council of Science Editors:
Vasalauskaite A. Visual function in human and experimental glaucoma. [Doctoral Dissertation]. Cardiff University; 2016. Available from: http://orca.cf.ac.uk/98604/
Cardiff University
6.
Rountree, Lindsay.
Optimisation of perimetric stimuli for mapping changes in spatial summation in glaucoma.
Degree: PhD, 2018, Cardiff University
URL: http://orca.cf.ac.uk/111180/
► Despite being considered the current reference standard for perimetric testing in glaucoma, standard automated perimetry has several cardinal limitations, including an unacceptably high test-retest variability,…
(more)
▼ Despite being considered the current reference standard for perimetric testing in glaucoma, standard automated perimetry has several cardinal limitations, including an unacceptably high test-retest variability, which increases with increasing depth of defect, and a limited useable dynamic range, with test-retest variability spanning almost the entire instrument range in advanced glaucomatous damage.
Prior studies have shown that spatial summation, the mechanism by which the visual system integrates light energy across the area of a stimulus, differs in disease, with an enlarged Ricco’s area (the limit of complete spatial summation) found in individuals with glaucoma. The aim of this work was to investigate whether a perimetric stimulus designed to exploit these changes in spatial summation would enable a greater signal/noise ratio (SNR) than that of the current standard stimulus, by directly measuring the displacement of the spatial summation function in glaucoma. Three stimulus forms were developed; one varying in area alone, one varying in both area and contrast simultaneously, and one varying in contrast alone, all operating within the local Ricco’s area. These novel stimuli were compared with the standard Goldmann III stimulus, in terms of disease signal, noise, and SNR.
The experiments presented in this thesis indicate that a stimulus modulating in area alone may offer greater benefits for measuring glaucomatous changes in spatial summation in a clinical setting, in the form of a greater disease signal, more uniform response variability with depth of defect, and greater SNR, when compared with the standard Goldmann III stimulus. Additionally, there is some indication that this stimulus is more robust to the effects of intraocular straylight than the Goldmann III stimulus, although test-retest variability and robustness to optical defocus are largely similar.
As this work represents the early investigations of this stimulus, further work is required to examine its translation into a clinical environment.
Subjects/Keywords: RE Ophthalmology
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APA ·
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Manager
APA (6th Edition):
Rountree, L. (2018). Optimisation of perimetric stimuli for mapping changes in spatial summation in glaucoma. (Doctoral Dissertation). Cardiff University. Retrieved from http://orca.cf.ac.uk/111180/
Chicago Manual of Style (16th Edition):
Rountree, Lindsay. “Optimisation of perimetric stimuli for mapping changes in spatial summation in glaucoma.” 2018. Doctoral Dissertation, Cardiff University. Accessed January 19, 2021.
http://orca.cf.ac.uk/111180/.
MLA Handbook (7th Edition):
Rountree, Lindsay. “Optimisation of perimetric stimuli for mapping changes in spatial summation in glaucoma.” 2018. Web. 19 Jan 2021.
Vancouver:
Rountree L. Optimisation of perimetric stimuli for mapping changes in spatial summation in glaucoma. [Internet] [Doctoral dissertation]. Cardiff University; 2018. [cited 2021 Jan 19].
Available from: http://orca.cf.ac.uk/111180/.
Council of Science Editors:
Rountree L. Optimisation of perimetric stimuli for mapping changes in spatial summation in glaucoma. [Doctoral Dissertation]. Cardiff University; 2018. Available from: http://orca.cf.ac.uk/111180/
Cardiff University
7.
Gaffney, Allannah J.
Characterising adaptational dysfunction in age-related macular degeneration.
Degree: PhD, 2012, Cardiff University
URL: http://orca.cf.ac.uk/41072/
► Age-related macular degeneration (AMD) is the leading cause of visual impairment in the developed world. The prevalence of this disease will continue to increase over…
(more)
▼ Age-related macular degeneration (AMD) is the leading cause of visual impairment in the developed world. The prevalence of this disease will continue to increase over the coming decades as the average age of the global population rises. There is consequently an urgent need to develop tests that are sensitive to early visual dysfunction, in order to identify individuals that have a high risk of developing AMD, to identify patients that would benefit from treatment, to assess the outcomes of that treatment and to evaluate emerging treatment strategies.
An emerging body of evidence suggests that dark adaptation is a sensitive biomarker for early AMD. Cone dark adaptation is of particular interest to clinicians, as it can identify patients with early AMD in a relatively short recording period. Consequently, this thesis aimed to optimise psychophysical and electrophysiological techniques for the assessment of cone dark adaptation in early AMD, in order to maximise its diagnostic potential.
A range of psychophysical methods were shown to be capable of monitoring the rapid changes in threshold that occur during cone dark adaptation. An optimal psychophysical protocol for the assessment of cone dark adaptation in early AMD was developed based on the results of a systematic evaluation of the effect of stimulus parameters and pre-adapting light intensity on the diagnostic potential of cone dark adaptation in early AMD. When compared to the focal cone ERG photostress test, both techniques were shown to be similarly diagnostic for early AMD. In addition, the time constant of cone recovery was shown to be significantly correlated with age, hence the sensitivity and specificity of cone dark adaptation as a biomarker for early macular disease may be further improved by considering these age-related changes.
In conclusion, this thesis has confirmed that cone dark adaptation is a sensitive functional biomarker for early AMD. However, as cross-sectional studies are unable to determine the true diagnostic potential of a biomarker, longitudinal investigations are needed to explore the long-term potential of cone dark adaptation and other visual functions as biomarkers for early AMD.
Subjects/Keywords: RE Ophthalmology
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APA (6th Edition):
Gaffney, A. J. (2012). Characterising adaptational dysfunction in age-related macular degeneration. (Doctoral Dissertation). Cardiff University. Retrieved from http://orca.cf.ac.uk/41072/
Chicago Manual of Style (16th Edition):
Gaffney, Allannah J. “Characterising adaptational dysfunction in age-related macular degeneration.” 2012. Doctoral Dissertation, Cardiff University. Accessed January 19, 2021.
http://orca.cf.ac.uk/41072/.
MLA Handbook (7th Edition):
Gaffney, Allannah J. “Characterising adaptational dysfunction in age-related macular degeneration.” 2012. Web. 19 Jan 2021.
Vancouver:
Gaffney AJ. Characterising adaptational dysfunction in age-related macular degeneration. [Internet] [Doctoral dissertation]. Cardiff University; 2012. [cited 2021 Jan 19].
Available from: http://orca.cf.ac.uk/41072/.
Council of Science Editors:
Gaffney AJ. Characterising adaptational dysfunction in age-related macular degeneration. [Doctoral Dissertation]. Cardiff University; 2012. Available from: http://orca.cf.ac.uk/41072/
Cardiff University
8.
Zayats, Tetyana.
Family study of high myopia: association studies.
Degree: PhD, 2010, Cardiff University
URL: http://orca.cf.ac.uk/54943/
► High myopia (more severe than -6.00 Diopters) is one of the leading causes of blindness and vision impairment in the world. Its prevalence has rapidly…
(more)
▼ High myopia (more severe than -6.00 Diopters) is one of the leading causes of blindness and vision impairment in the world. Its prevalence has rapidly been growing and the estimated number of myopic people worldwide is expected to be 2.5 billion by the year 2020. My experimental work covered three topics: (1) characterization of the quantity and quality of mouth wash-extracted DNA (2) genetic association studies, and (3) evaluation of an imprinting effect in high myopia. Mouthwash-derived DNA is an important source of human DNA for large-scale genetic studies. Thus, potential methods of DNA quantification (spectrophotometry, fluorometry, gel electrophoresis and qPCR) and quality assessment (gel electrophoresis and PCR) were evaluated. Regarding DNA quantification methods, fluorometry compared favorably to the gold-standard qPCR. DNA quality assessments revealed that -10% of collected buccal DNA samples were severely degraded—a phenomenon that was shown to be partly subject-specific. Myopia association studies were performed for: genes in MYP regions, the myocilin gene, the collagen type I alpha 1 gene and the collagen type II alpha 1 gene. These genes have been linked to myopia because of their function and/or previous positive findings. All tests were performed on a combined dataset of complex high myopia pedigrees and cases/controls, applying likelihood ratio statistics and Bonferroni correction to account for multiple testing. The results suggested that none of the genes examined have an important influence on susceptibility to high myopia. There is greater resemblance of refractive error between siblings than between parents and offspring, implying the possibility of imprinting in the aetiology of myopia. Thus, tests for imprinting were performed on "trio" pedigrees, applying Z-score and T2-test statistics and permutation to account for multiple testing. The results tentatively suggested that parent-of- origin effects and/or by maternal effects contribute to myopia development.
Subjects/Keywords: RE Ophthalmology
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APA ·
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Manager
APA (6th Edition):
Zayats, T. (2010). Family study of high myopia: association studies. (Doctoral Dissertation). Cardiff University. Retrieved from http://orca.cf.ac.uk/54943/
Chicago Manual of Style (16th Edition):
Zayats, Tetyana. “Family study of high myopia: association studies.” 2010. Doctoral Dissertation, Cardiff University. Accessed January 19, 2021.
http://orca.cf.ac.uk/54943/.
MLA Handbook (7th Edition):
Zayats, Tetyana. “Family study of high myopia: association studies.” 2010. Web. 19 Jan 2021.
Vancouver:
Zayats T. Family study of high myopia: association studies. [Internet] [Doctoral dissertation]. Cardiff University; 2010. [cited 2021 Jan 19].
Available from: http://orca.cf.ac.uk/54943/.
Council of Science Editors:
Zayats T. Family study of high myopia: association studies. [Doctoral Dissertation]. Cardiff University; 2010. Available from: http://orca.cf.ac.uk/54943/
Cardiff University
9.
Gill, Felicity Rosemary.
Turning the tide for gas permeable contact lenses.
Degree: PhD, 2010, Cardiff University
URL: http://orca.cf.ac.uk/54980/
► Gas permeable (GP) lens materials and design technology have advanced in recent years and GP lenses are recognised as providing the wearer with a reduced…
(more)
▼ Gas permeable (GP) lens materials and design technology have advanced in recent years and GP lenses are recognised as providing the wearer with a reduced risk of serious sight-threatening complications, better vision and better long-term comfort. Yet despite these advantages, GP lens prescribing in the UK remains in decline. This thesis investigates how the decline might be addressed by studying the influence of prescribing habits, fitting strategies and lens surface treatments. Initially a questionnaire was designed to investigate practitioner attitudes and behaviour toward GP lenses, and to ascertain whether eye care practitioner (ECP) reservations were responsible for prescribing decline. This survey found that, despite ECP awareness of the advantages of GP lenses, the challenges of reduced initial comfort and increased time required in fitting, results in significant negative practitioner attitudes. In an effort to address the reservations discovered, an investigation of topical anaesthetic (TA) instillation prior to GP fitting was performed in a large case-control study. The results demonstrated that this practice has no negative clinical impact on the ocular surface, marginally improves patient comfort at fitting, and significantly reduces patient anxiety prior to successive GP lens insertion. The remainder of this thesis presents the results from a longitudinal study where groups of neophyte and soft lens wearers were fitted with GP lenses for three months with and without plasma surface treatment (PST). Subjects were monitored and lenses harvested for surface analysis using atomic force microscopy. Examination of GP lenses demonstrated that PST produces smoother surface topographies, prior to and following wear, but this difference reduces after three months wear. Subjects previously wearing soft lenses report lower levels of comfort than neophytes, and PST does not seem to enhance the experience for either group in this cohort. In summary, this thesis presents important findings about the influence of initial comfort on patient anxiety and practitioner attitudes towards GP lens fitting, and gives important insights into the impact of plasma treatment on comfort and performance over the first three months of lens wear.
Subjects/Keywords: RE Ophthalmology
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APA ·
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MLA ·
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Manager
APA (6th Edition):
Gill, F. R. (2010). Turning the tide for gas permeable contact lenses. (Doctoral Dissertation). Cardiff University. Retrieved from http://orca.cf.ac.uk/54980/
Chicago Manual of Style (16th Edition):
Gill, Felicity Rosemary. “Turning the tide for gas permeable contact lenses.” 2010. Doctoral Dissertation, Cardiff University. Accessed January 19, 2021.
http://orca.cf.ac.uk/54980/.
MLA Handbook (7th Edition):
Gill, Felicity Rosemary. “Turning the tide for gas permeable contact lenses.” 2010. Web. 19 Jan 2021.
Vancouver:
Gill FR. Turning the tide for gas permeable contact lenses. [Internet] [Doctoral dissertation]. Cardiff University; 2010. [cited 2021 Jan 19].
Available from: http://orca.cf.ac.uk/54980/.
Council of Science Editors:
Gill FR. Turning the tide for gas permeable contact lenses. [Doctoral Dissertation]. Cardiff University; 2010. Available from: http://orca.cf.ac.uk/54980/
Cardiff University
10.
Handzel, Kinga Elzbieta.
Role of visual pigment in primary events leading to retinal dysfunction and development of age-related macular degeneration.
Degree: PhD, 2010, Cardiff University
URL: http://orca.cf.ac.uk/55009/
► The aim of this study was to gain a deeper understanding of the role of the visual pigment in retinal damage and its contribution to…
(more)
▼ The aim of this study was to gain a deeper understanding of the role of the visual pigment in retinal damage and its contribution to initial pathways in the pathogenesis of age-related macular-degeneration (AMD). Initially, the kinetics of all-trans-retinal (ATR) hydrolysis from opsin and its reduction to retinol formation were determined. Based on the results, singlet oxygen generation was investigated as a function of ATR position and the availability of cofactors required for retinol formation. The yield of singlet oxygen generated by ATR increased upon hydrolysis of ATR from opsin and further, upon its release to the disc membrane. The presence of ATP and NADPH did not influence the signals significantly. (Photo)cytotoxicity studies revealed that both ATR and its degradation products (dATR) are toxic to cells, with dATR having a more deleterious effect. Toxic effects of dATR were prevented by a-tocopherol, retinol and phosphatidylethanolamine, whereas none of hydrophilic antioxidants tested exerted a substantial effect. Both ATR and dATR exhibited a similar ability to generate singlet oxygen when excited with visible light, whereas products of ATR degradation were characterised by greater photosensitising properties than ATR for shorter wavelengths. The yield of singlet oxygen for retinol was lower than for ATR in acetone. Although, retinyl ascorbate has a great potential to be a strong singlet oxygen quencher, the difference in the quenching rate was not found to be statistically significant when compared with all-trans-retinol or ascorbyl palmitate. Accumulation of products of rhodopsin bleaching increased the formation of lipofuscin-like inclusion bodies. Exposure of cells to light was associated with higher levels of fluorescence characteristic for oxidised cellular components. In summary, the results suggest that products of visual pigment bleaching may contribute to the toxic effects of light on the retina. In conjunction with published findings, it supports the theory that ATR can play an important role in causing RPE dysfunction as occurring in retinal aging and AMD.
Subjects/Keywords: RE Ophthalmology
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APA (6th Edition):
Handzel, K. E. (2010). Role of visual pigment in primary events leading to retinal dysfunction and development of age-related macular degeneration. (Doctoral Dissertation). Cardiff University. Retrieved from http://orca.cf.ac.uk/55009/
Chicago Manual of Style (16th Edition):
Handzel, Kinga Elzbieta. “Role of visual pigment in primary events leading to retinal dysfunction and development of age-related macular degeneration.” 2010. Doctoral Dissertation, Cardiff University. Accessed January 19, 2021.
http://orca.cf.ac.uk/55009/.
MLA Handbook (7th Edition):
Handzel, Kinga Elzbieta. “Role of visual pigment in primary events leading to retinal dysfunction and development of age-related macular degeneration.” 2010. Web. 19 Jan 2021.
Vancouver:
Handzel KE. Role of visual pigment in primary events leading to retinal dysfunction and development of age-related macular degeneration. [Internet] [Doctoral dissertation]. Cardiff University; 2010. [cited 2021 Jan 19].
Available from: http://orca.cf.ac.uk/55009/.
Council of Science Editors:
Handzel KE. Role of visual pigment in primary events leading to retinal dysfunction and development of age-related macular degeneration. [Doctoral Dissertation]. Cardiff University; 2010. Available from: http://orca.cf.ac.uk/55009/
Cardiff University
11.
Cui, Liu.
Effects of eccentricity, contrast, orientation and the number and length of grating bars on orientation discrimination.
Degree: PhD, 2010, Cardiff University
URL: http://orca.cf.ac.uk/55017/
► Ei indicates the eccentricity where stimulus size must double to maintain performance equivalent to that at fovea. An over 200-fold range of Ei has been…
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▼ Ei indicates the eccentricity where stimulus size must double to maintain performance equivalent to that at fovea. An over 200-fold range of Ei has been found using spatial scaling since the introduction of method. Some later research in orientation discrimination suggested that contrast reduction elevated Ei (Sally and Gurnesy 2003, 2004 and 2007). However, it was based on very limited data. Therefore, to examine how Ej changes with contrast, two types of orientation discrimination tasks involving six experiments were studied using spatial scaling in the thesis: (i) orientation discrimination at 10-100% contrasts and 0-10 degree eccentricities using Gaussian-filtered lines and 2-16 cycles-per-image (cpi) gratings, and (ii) contrast thresholds allowing discrimination of 1.5-45 degrees orientation differences (OD) at 0-10 degree eccentricities using the same stimuli for the first task. Three hypotheses were made: (i) when the effect of contrast was taken into account, the peripheral stimulus size required for performance equivalent to that of the fovea can be obtained at a range of contrasts by spatial scaling, and (ii) for low-cycle-number (<16 cpi) grating stimulus, the number of cycles played a crucial role on the visual performance across visual field, and (iii) for the threshold contrast of a fixed orientation difference discrimination, the visual process mechanism of the visual task at large orientation difference was different from that at small difference close to orientation discrimination threshold. The results of the orientation discrimination experiments showed that (i) spatial scaling succeeded in superimposing all the threshold data across contrasts or within a contrast, meaning that there is no qualitative difference between the fovea and periphery, (ii) E2 was independent of contrast, suggesting that contrast reduction had no different influence on spatial summation in between foveal and peripheral visual field, (iii) Ei decreased and saturated with increasing cpi, indicating that for low-cycle-number grating stimulus, the cycle number played a crucial role on the visual performance. The results of the contrast threshold allowing the fixed orientation discrimination experiments showed that (i) the task complexity resulted in the failure of spatial scaling for superimposing all the threshold data across orientation differences, (ii) spatial Ei increased and saturated with increasing cpi, suggesting more size scaling needed for achieving foveal levels of performance for smaller cpi stimulus, and (iii) Ej found in 1.5 deg orientation difference was much smaller than those at other differences, suggesting that the visual process mechanism at large OD was different from that at OD as small as orientation discrimination threshold.
Subjects/Keywords: RE Ophthalmology
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APA (6th Edition):
Cui, L. (2010). Effects of eccentricity, contrast, orientation and the number and length of grating bars on orientation discrimination. (Doctoral Dissertation). Cardiff University. Retrieved from http://orca.cf.ac.uk/55017/
Chicago Manual of Style (16th Edition):
Cui, Liu. “Effects of eccentricity, contrast, orientation and the number and length of grating bars on orientation discrimination.” 2010. Doctoral Dissertation, Cardiff University. Accessed January 19, 2021.
http://orca.cf.ac.uk/55017/.
MLA Handbook (7th Edition):
Cui, Liu. “Effects of eccentricity, contrast, orientation and the number and length of grating bars on orientation discrimination.” 2010. Web. 19 Jan 2021.
Vancouver:
Cui L. Effects of eccentricity, contrast, orientation and the number and length of grating bars on orientation discrimination. [Internet] [Doctoral dissertation]. Cardiff University; 2010. [cited 2021 Jan 19].
Available from: http://orca.cf.ac.uk/55017/.
Council of Science Editors:
Cui L. Effects of eccentricity, contrast, orientation and the number and length of grating bars on orientation discrimination. [Doctoral Dissertation]. Cardiff University; 2010. Available from: http://orca.cf.ac.uk/55017/
Cardiff University
12.
Kisiswa, Lilian.
Role of inhibitors of apoptosis (IAPs) in retinal ganglion cell death and dendrite remodelling.
Degree: PhD, 2010, Cardiff University
URL: http://orca.cf.ac.uk/55022/
► Neuronal viability and connectivity is essential for neuronal function in heath and disease. The aim of this study was to elucidate factors and mechanisms that…
(more)
▼ Neuronal viability and connectivity is essential for neuronal function in heath and disease. The aim of this study was to elucidate factors and mechanisms that govern the maintenance and remodelling of RGC dendrites, as well as neuronal cell death in ageing and neurodegenerative diseases. Using PCR technique, the expression pattern of caspases 3,6-9 and inhibitors of apoptosis (lAPs), namely neuronal IAP (NIAP), cellular IAP1 and 2 (clAP1 and 2), X-chromosome linked IAP (XIAP), Survivin, Bruce and Livin was determined in young adult (6 weeks), mature (24-52 weeks), old (88 weeks) and diseased retinae of Wistar albino and Brown Norway (BN) rats. Caspase expression was not altered during maturation and ageing in both strains. In ageing Wistar, NIAP, clAP2 and XIAP and clAP1 were decreased in 88 compared to 24-52 weeks, while Survivin, Bruce and Livin were slightly increased with age. lAPs expression was generally decreased in mature (24- 52 weeks) BN retinae compared to younger (6 weeks). Furthermore, validation of the expression of these molecules at protein level was carried out using western blotting and immunofluorescence techniques. clAP1 protein levels were downregulated in RGCL of BN rats. Reduction of clAP1 did not alter caspase activity but led to impairment in the survival pathway. Older BN retinae demonstrated compromised RGC morphology, but there was no retinal cell loss. Microbead experimental glaucoma model demonstrated no alteration in caspase expression upon induction of glaucoma. NIAP, clAP2, Survivin and Livin were up-regulated, while Bruce was down-regulated in glaucomatous eyes. clAP1 and XIAP expression remain similar between control and experimental eye. In conclusion, reduction in lAPs, which may lead to impairment in survival pathways might be the underlaying cause of reduction in dendrite complexity. Compromised RGC morphology makes a preparatory platform for neurodegenerative process observed in glaucoma disease where age is a major risk factor.
Subjects/Keywords: RE Ophthalmology
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APA (6th Edition):
Kisiswa, L. (2010). Role of inhibitors of apoptosis (IAPs) in retinal ganglion cell death and dendrite remodelling. (Doctoral Dissertation). Cardiff University. Retrieved from http://orca.cf.ac.uk/55022/
Chicago Manual of Style (16th Edition):
Kisiswa, Lilian. “Role of inhibitors of apoptosis (IAPs) in retinal ganglion cell death and dendrite remodelling.” 2010. Doctoral Dissertation, Cardiff University. Accessed January 19, 2021.
http://orca.cf.ac.uk/55022/.
MLA Handbook (7th Edition):
Kisiswa, Lilian. “Role of inhibitors of apoptosis (IAPs) in retinal ganglion cell death and dendrite remodelling.” 2010. Web. 19 Jan 2021.
Vancouver:
Kisiswa L. Role of inhibitors of apoptosis (IAPs) in retinal ganglion cell death and dendrite remodelling. [Internet] [Doctoral dissertation]. Cardiff University; 2010. [cited 2021 Jan 19].
Available from: http://orca.cf.ac.uk/55022/.
Council of Science Editors:
Kisiswa L. Role of inhibitors of apoptosis (IAPs) in retinal ganglion cell death and dendrite remodelling. [Doctoral Dissertation]. Cardiff University; 2010. Available from: http://orca.cf.ac.uk/55022/
Cardiff University
13.
Chen, Yen-Po.
Role of genetics in susceptibility to environmentally-induced myopia.
Degree: PhD, 2011, Cardiff University
URL: http://orca.cf.ac.uk/55049/
► Myopia is a common ocular disorder with complex and yet unidentified causes. Studies in animal models of myopia have revealed substantial variation in the degree…
(more)
▼ Myopia is a common ocular disorder with complex and yet unidentified causes. Studies in animal models of myopia have revealed substantial variation in the degree of myopia induced by a uniform regimen of visual manipulation. This study investigated the role of genetics on susceptibility to environmentally-induced myopia by means of a selective breeding experiment. Chicks with high or low susceptibility to monocular form deprivation (FD) were selected from an outbred population that showed considerable variation in the response to FD. After two rounds of selection, the High and Low susceptibility selected lines exhibited an evident divergence in their ocular responses to FD. Chicks from the High line developed twice the degree of myopia compared to those from the Low line. This difference was not due to visual disability or immaturity of the visual system in Low line chicks. Thus, susceptibility to form deprivation in chicks has a strong genetic component. In estimating the heritability, approximately 50% of the variation in the chicks' susceptibility to FD-induced myopia was attributable to additive genetic effects. However, the genetic variants that control the normal variation in eye size appear to be distinct from the variants that determine susceptibility to FD due to no evidence of pleiotropic genetic effects between these traits. When chicks from the High and Low lines were tested for their responses to lens- induced visual defocus, a significant difference between the two selected lines was observed for minus lens wear, but not for plus lens wear. Thus, there must be some shared mechanism(s) in the ocular responses to FD and minus lens wear, but different mechanisms in the responses to plus lens wear and FD. Compared to the chicken, the mouse model of myopia has the advantages of a closer evolutionary relationship to humans and features of primate myopia. Using a novel swept-source OCT system, it was found that OCT showed good repeatability and accuracy in measuring axial ocular components in mouse. In addition, axial ocular components in mice were found to be mainly controlled by additive genetic effects.
Subjects/Keywords: RE Ophthalmology
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APA ·
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APA (6th Edition):
Chen, Y. (2011). Role of genetics in susceptibility to environmentally-induced myopia. (Doctoral Dissertation). Cardiff University. Retrieved from http://orca.cf.ac.uk/55049/
Chicago Manual of Style (16th Edition):
Chen, Yen-Po. “Role of genetics in susceptibility to environmentally-induced myopia.” 2011. Doctoral Dissertation, Cardiff University. Accessed January 19, 2021.
http://orca.cf.ac.uk/55049/.
MLA Handbook (7th Edition):
Chen, Yen-Po. “Role of genetics in susceptibility to environmentally-induced myopia.” 2011. Web. 19 Jan 2021.
Vancouver:
Chen Y. Role of genetics in susceptibility to environmentally-induced myopia. [Internet] [Doctoral dissertation]. Cardiff University; 2011. [cited 2021 Jan 19].
Available from: http://orca.cf.ac.uk/55049/.
Council of Science Editors:
Chen Y. Role of genetics in susceptibility to environmentally-induced myopia. [Doctoral Dissertation]. Cardiff University; 2011. Available from: http://orca.cf.ac.uk/55049/
Cardiff University
14.
Davies, Jennifer Rhian.
Neuro-ophthalmological syndrome 3-methylglutaconic aciduria: a molecular and functional study of the B6; C3-Opa3L122P mouse model.
Degree: PhD, 2011, Cardiff University
URL: http://orca.cf.ac.uk/55053/
► Introduction: OPA3 is the causative gene of the autosomal recessive, multi-systemic neuro- ophthalmological syndrome, 3-methylglutaconic aciduria Type III (MGA-III) and Autosomal Dominant Optic Atrophy and…
(more)
▼ Introduction: OPA3 is the causative gene of the autosomal recessive, multi-systemic neuro- ophthalmological syndrome, 3-methylglutaconic aciduria Type III (MGA-III) and Autosomal Dominant Optic Atrophy and Cataract (ADOAC). Early onset bilateral optic atrophy is a common characteristic of both disorders where retinal ganglion cells (RGCs) are lost. Purpose: To investigate the pathophysiology of the disease and function of the OPA3 protein we generated a novel ENU-induced mutant mouse carrying the missense mutation p.L122P in exon 2 of Opa3 which is predicted to alter tertiary protein structure. Methods: Visual function was assessed using optokinetic nystagmus and pupillary light reflex. Histology explored retinal degeneration and metabolic dysfunction. Rotarod, wirehang and open field analysed neurological, neuromuscular and behavioural aspects of the disease. Genomic structure of Opa3 was re-examined using RT-PCR and bio-informatic programs characterized possible upstream transcription factor binding sites (TFBS). Results: Opa3 ' mice displayed a multi-systemic disease, including decreased life span and weight, extra-pyramidal dysfunction, neuro-muscular defect, craniofacial defects, reduction in intra-abdominal white adipose tissue, elevated marrow adiposity and severe hepatic steatosis. Opa3'' are functionally blind but pupillary function was essentially intact. Histology showed loss of RGCs and other cell types through postnatal development onwards. RT-PCR identified a third exon and analysis of 53 TFBS identified suggests a role for Opa3 in retinal and craniofacial development, cellular stress response/apoptosis and adipogenesis. Conclusions: Opa3 / display many aspects of human MGA-III syndrome and phenotypes not observed such as craniofacial defects and a profound disturbance in lipid metabolism. Opa3 is thought to be involved in the mevalonate shunt and leucine degradation metabolic pathways. Defects in these pathways can cause a build up of 3-methylglutaconic acid and 3- methylglyaric acid in the inner mitochondrial membrane which may have a profound affect on mitochondrial metabolism particularly in high energy demand tissues such as retina, heart and neurons.
Subjects/Keywords: RE Ophthalmology
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APA (6th Edition):
Davies, J. R. (2011). Neuro-ophthalmological syndrome 3-methylglutaconic aciduria: a molecular and functional study of the B6; C3-Opa3L122P mouse model. (Doctoral Dissertation). Cardiff University. Retrieved from http://orca.cf.ac.uk/55053/
Chicago Manual of Style (16th Edition):
Davies, Jennifer Rhian. “Neuro-ophthalmological syndrome 3-methylglutaconic aciduria: a molecular and functional study of the B6; C3-Opa3L122P mouse model.” 2011. Doctoral Dissertation, Cardiff University. Accessed January 19, 2021.
http://orca.cf.ac.uk/55053/.
MLA Handbook (7th Edition):
Davies, Jennifer Rhian. “Neuro-ophthalmological syndrome 3-methylglutaconic aciduria: a molecular and functional study of the B6; C3-Opa3L122P mouse model.” 2011. Web. 19 Jan 2021.
Vancouver:
Davies JR. Neuro-ophthalmological syndrome 3-methylglutaconic aciduria: a molecular and functional study of the B6; C3-Opa3L122P mouse model. [Internet] [Doctoral dissertation]. Cardiff University; 2011. [cited 2021 Jan 19].
Available from: http://orca.cf.ac.uk/55053/.
Council of Science Editors:
Davies JR. Neuro-ophthalmological syndrome 3-methylglutaconic aciduria: a molecular and functional study of the B6; C3-Opa3L122P mouse model. [Doctoral Dissertation]. Cardiff University; 2011. Available from: http://orca.cf.ac.uk/55053/
Cardiff University
15.
Ho, Leona T.Y.
Glycosaminoglycans and collagen fibril organization in corneal tissue.
Degree: PhD, 2011, Cardiff University
URL: http://orca.cf.ac.uk/55103/
► Hypothesis: The hypothesis of this research is that changes in the sulphation patterns of the glycosaminoglycans are directly related to changes in ultrastructure, and hence…
(more)
▼ Hypothesis: The hypothesis of this research is that changes in the sulphation patterns of the glycosaminoglycans are directly related to changes in ultrastructure, and hence transparency of the cornea. Aims: The aims of this research were to investigate glycosaminoglycan sulphation patterns and collagen fibril ultrastructure from central to peripheral regions of the cornea, and to gain a greater understanding in the effects of keratan sulphate and its reliance on oxygen supply. Methods: The bovine corneal extracellular matrix composition and collagen fibril parameters (fibril diameter and interfibrillar spacing) were biochemically and biophysically evaluated. This involved taking measurements of corneal thickness and hydration, as well as the amount of hydroxyproline and sulphated glycosaminoglycan. Immunolocalization of proteoglycan protein cores (lumican and keratocan) and specific glycosaminoglycans, particularly their sulphation distribution were studied using specific antibodies. Sulphation patterns of keratan sulphate were also quantified using specific antibodies. Transmission electron microscopy coupled with synchrotron small angle x-ray fibre diffraction was also employed to gain a greater understanding of the corneas' collagen fibril architecture and its interaction with glycosaminoglycans across the depths of the cornea. Results: The bovine cornea is thicker in the outer peripheral regions of the cornea and accordingly an increased amount of hydroxyproline is found at this region of the tissue. Keratan sulphate is predominantly found in the bovine cornea and is particularly heavily sulphated across the cornea. The degree of sulphation of keratan sulphate decreases at the outer peripheral regions of the cornea, which, interestingly, is where a transition of collagen fibrils occurs in that fibrils become less uniformly arranged, changes in fibril diameter are seen, and interfibrillar spacing values alter. Depth- profiled synchrotron microbeam analyses show that at different radial positions, from the corneal centre outwards, fibril diameter is greater superficially than in deep stromal regions. This does not include Bowman's layer which is below the spatial resolution of the analysis. The mid-depth stroma has higher interfibrillar spacing than is seen in posterior regions of the stroma, where fibril spacing appeared more compact. Previous work has pointed to a link between glycosaminoglycan content and oxygen availability. Work presented here indicates that in rabbit corneas, after 24 hr in 2% atmospheric O2, the glycosaminoglycan sulphation pattern changes significantly, with a significant increase of the high sulphated epitope of keratan sulphate. Conclusion: My data reveal that collagen fibrils in the central regions of the cornea are more closely packed and uniform in diameter than those in the outer peripheral cornea, and this may have potential implications for the transparency of the tissue. Stromal architecture is likely governed by sulphated proteoglycans, and changes in the types and sulphation…
Subjects/Keywords: RE Ophthalmology
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APA (6th Edition):
Ho, L. T. Y. (2011). Glycosaminoglycans and collagen fibril organization in corneal tissue. (Doctoral Dissertation). Cardiff University. Retrieved from http://orca.cf.ac.uk/55103/
Chicago Manual of Style (16th Edition):
Ho, Leona T Y. “Glycosaminoglycans and collagen fibril organization in corneal tissue.” 2011. Doctoral Dissertation, Cardiff University. Accessed January 19, 2021.
http://orca.cf.ac.uk/55103/.
MLA Handbook (7th Edition):
Ho, Leona T Y. “Glycosaminoglycans and collagen fibril organization in corneal tissue.” 2011. Web. 19 Jan 2021.
Vancouver:
Ho LTY. Glycosaminoglycans and collagen fibril organization in corneal tissue. [Internet] [Doctoral dissertation]. Cardiff University; 2011. [cited 2021 Jan 19].
Available from: http://orca.cf.ac.uk/55103/.
Council of Science Editors:
Ho LTY. Glycosaminoglycans and collagen fibril organization in corneal tissue. [Doctoral Dissertation]. Cardiff University; 2011. Available from: http://orca.cf.ac.uk/55103/
Cardiff University
16.
Parfitt, Geraint.
Proteoglycans as dynamic regulators of the organised collagen fibril architecture in the cornea: an electron tomography study of the mouse corneal stroma.
Degree: PhD, 2011, Cardiff University
URL: http://orca.cf.ac.uk/55104/
► The cornea is the primary refractive element of the eye and is also fundamental to the protection of the visual system. Collagen is the major…
(more)
▼ The cornea is the primary refractive element of the eye and is also fundamental to the protection of the visual system. Collagen is the major constituent of the cornea, where it is organised in a lattice that enables corneal transparency. Proteoglycan macromolecules are thought to regulate the diameter and spatial order of collagen fibrils in the cornea, which are both pre-requisites for corneal transparency, although the mechanisms by which they organise fibrils are not fully elucidated. This investigation examined the morphology, morphometry and organisation of proteoglycans three-dimensionally, in both normal and genetically altered mouse corneas, to gain a greater understanding of proteoglycan structure-function relationships. In summary, we found that proteoglycans are primarily responsible for the remarkable collagen organisation in the mouse cornea, which allows for corneal transparency. The self- association of proteoglycans into complexes is likely to result in a robust attachment of neighbouring fibrils and provides biomechanical strength, whilst sulphation patterns are seen to have a direct effect on the aggregation potential of proteoglycans. Removal of proteoglycans, particularly lumican, affects the regulation of both fibril size and spatial order, both required for corneal transparency.
Subjects/Keywords: RE Ophthalmology
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APA (6th Edition):
Parfitt, G. (2011). Proteoglycans as dynamic regulators of the organised collagen fibril architecture in the cornea: an electron tomography study of the mouse corneal stroma. (Doctoral Dissertation). Cardiff University. Retrieved from http://orca.cf.ac.uk/55104/
Chicago Manual of Style (16th Edition):
Parfitt, Geraint. “Proteoglycans as dynamic regulators of the organised collagen fibril architecture in the cornea: an electron tomography study of the mouse corneal stroma.” 2011. Doctoral Dissertation, Cardiff University. Accessed January 19, 2021.
http://orca.cf.ac.uk/55104/.
MLA Handbook (7th Edition):
Parfitt, Geraint. “Proteoglycans as dynamic regulators of the organised collagen fibril architecture in the cornea: an electron tomography study of the mouse corneal stroma.” 2011. Web. 19 Jan 2021.
Vancouver:
Parfitt G. Proteoglycans as dynamic regulators of the organised collagen fibril architecture in the cornea: an electron tomography study of the mouse corneal stroma. [Internet] [Doctoral dissertation]. Cardiff University; 2011. [cited 2021 Jan 19].
Available from: http://orca.cf.ac.uk/55104/.
Council of Science Editors:
Parfitt G. Proteoglycans as dynamic regulators of the organised collagen fibril architecture in the cornea: an electron tomography study of the mouse corneal stroma. [Doctoral Dissertation]. Cardiff University; 2011. Available from: http://orca.cf.ac.uk/55104/
Cardiff University
17.
Rattan, Rishi.
The development of dynamic noise perimetry.
Degree: PhD, 2010, Cardiff University
URL: http://orca.cf.ac.uk/55177/
► This thesis describes the developm ent o f Dynamic Noise Perimetry (DNP), a novel method based on the equivalent noise input technique. The method, specifically…
(more)
▼ This thesis describes the developm ent o f Dynamic Noise Perimetry (DNP), a novel method based on the equivalent noise input technique. The method, specifically targeted to an early stage o f OAG, used a 0.5 cycle per degree sine-wave grating presented at 8Hz in conjunction with an external noise m ask that was optimised for the stimulus. Equivalent noise and sampling efficiency w ere determ ined at various locations within the visual field to identify a stage o f the disease that was analogous to ganglion cell shrinkage, a stage which is believed to precede conventional methods o f detection. A pilot study initially determ ined w hether the spatial parameters o f the mask, in terms o f noise check size, were dependent on the spatial and temporal param eters o f the grating stimulus. The results show ed that the m axim al dimensions o f each check, i.e. the critical check size, were correlated w ith the drift frequency o f the stimulus. In a second and preliminary study, the variation in the critical check size with grating spatial and temporal frequency was investigated as a function o f eccentricity. Critical noise check size, in terms o f noise checks per cycle, decreased w ith increasing spatial frequency and drift frequency o f the stimulus, and with eccentric viewing. These results were used to optim ise the critical parameters for the noise mask. Temporal contrast sensitivity, equivalent noise and sampling efficiency were determined at various locations in the visual field, in 20 normal individuals and in 10 individuals with OAG. Temporal contrast sensitivity was reduced, and equivalent noise levels were elevated in early OAG, w hen com pared with normal individuals. Derivative measures o f sampling efficiency and equivalent noise declined with glaucomatous field loss. DNP was able to identify individuals w ith OAG, at locations which exhibited abnormal Pattern Deviation values and/ or abnorm al retinal nerve fibre layer thickness. DNP clearly warrants further development
Subjects/Keywords: RE Ophthalmology
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APA (6th Edition):
Rattan, R. (2010). The development of dynamic noise perimetry. (Doctoral Dissertation). Cardiff University. Retrieved from http://orca.cf.ac.uk/55177/
Chicago Manual of Style (16th Edition):
Rattan, Rishi. “The development of dynamic noise perimetry.” 2010. Doctoral Dissertation, Cardiff University. Accessed January 19, 2021.
http://orca.cf.ac.uk/55177/.
MLA Handbook (7th Edition):
Rattan, Rishi. “The development of dynamic noise perimetry.” 2010. Web. 19 Jan 2021.
Vancouver:
Rattan R. The development of dynamic noise perimetry. [Internet] [Doctoral dissertation]. Cardiff University; 2010. [cited 2021 Jan 19].
Available from: http://orca.cf.ac.uk/55177/.
Council of Science Editors:
Rattan R. The development of dynamic noise perimetry. [Doctoral Dissertation]. Cardiff University; 2010. Available from: http://orca.cf.ac.uk/55177/
18.
Ng, Alison Yuk San.
The Effects of Eye Cosmetics on the Ocular Surface and Tear Film.
Degree: PhD, 2013, Cardiff Univesity
URL: http://orca.cf.ac.uk/59398/
► Eye cosmetics usage in the UK is commonplace. Despite its popularity, there is a lack of published literature exploring the ocular effects of eye cosmetic…
(more)
▼ Eye cosmetics usage in the UK is commonplace. Despite its popularity, there is a lack of published literature exploring the ocular effects of eye cosmetic usage. The influence of eye cosmetics upon symptoms of dry eye and contact lens discomfort has been suggested but these links have not been established. Consequently, this thesis aims to establish any link between ocular comfort with eye cosmetic usage. This was achieved by conducting a survey which showed the use of eye cosmetics, particularly eyeliner, significantly reduced ocular comfort. Amongst cosmetic users, contact lens wearers did not experience significantly reduced ocular comfort compared to non-contact lens wearers.
Eye care practitioners often report observations of eye cosmetics contaminating the tear film, even when the products are applied to peri-ocular skin, although these reports are anecdotal. This thesis demonstrates that cosmetic pencil eyeliner migrates most readily and maximally contaminates the tear film when applied along the inner lid margin. After two hours post-application, contamination of the tear film from pencil eyeliner was negligible.
This finding led to a subsequent study which examined the clinical and immunological responses of the ocular surface following migration of cosmetic pencil eyeliner. Clinically, eyeliner pencil did not appear to induce signs of ocular surface inflammation. However seven consecutive days of eyeliner application along the inner lid margin increased lipid layer thickness and dry eye symptoms compared to when the eyeliner was applied to peri-ocular eyelid skin. Subclinical signs of ocular surface inflammation were investigated by examining the concentration of inflammatory cytokines, IL-6 and IL-8, in tear fluid. A small reduction of cytokine concentration was exhibited after one day of eyeliner use although concentrations returned to near baseline levels after seven days of use. In conclusion, pencil eyeliner is safe to use and does not appear to induce clinical or subclinical signs of inflammation when used for up to seven days consecutively. The causes of increased dry eye symptoms are undetermined and the longer term effects of eyeliner application remain unknown.
Subjects/Keywords: RE Ophthalmology
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APA (6th Edition):
Ng, A. Y. S. (2013). The Effects of Eye Cosmetics on the Ocular Surface and Tear Film. (Doctoral Dissertation). Cardiff Univesity. Retrieved from http://orca.cf.ac.uk/59398/
Chicago Manual of Style (16th Edition):
Ng, Alison Yuk San. “The Effects of Eye Cosmetics on the Ocular Surface and Tear Film.” 2013. Doctoral Dissertation, Cardiff Univesity. Accessed January 19, 2021.
http://orca.cf.ac.uk/59398/.
MLA Handbook (7th Edition):
Ng, Alison Yuk San. “The Effects of Eye Cosmetics on the Ocular Surface and Tear Film.” 2013. Web. 19 Jan 2021.
Vancouver:
Ng AYS. The Effects of Eye Cosmetics on the Ocular Surface and Tear Film. [Internet] [Doctoral dissertation]. Cardiff Univesity; 2013. [cited 2021 Jan 19].
Available from: http://orca.cf.ac.uk/59398/.
Council of Science Editors:
Ng AYS. The Effects of Eye Cosmetics on the Ocular Surface and Tear Film. [Doctoral Dissertation]. Cardiff Univesity; 2013. Available from: http://orca.cf.ac.uk/59398/
Cardiff University
19.
Morgan, Sian.
Understanding the structural basis of corneal refractive function and its modification via novel therapeutic approaches.
Degree: PhD, 2014, Cardiff University
URL: http://orca.cf.ac.uk/59401/
► The studies comprising this thesis were conducted to further understand how structural changes to the corneal extracellular matrix can affect the cornea’s unique properties, with…
(more)
▼ The studies comprising this thesis were conducted to further understand how structural changes to the corneal extracellular matrix can affect the cornea’s unique properties, with the ultimate goal of improving novel treatments and their outcomes. Following refractive surgery, changes in matrix structure can cause loss of structural integrity and transparency, which may adversely affect the surgical outcome. The first objective was to define what governs corneal shape and ultrastructural organisation by analysing the abnormal post-hatch corneal collagen arrangement in an avian model (beg). Structural information was also obtained post-in vivo microwave keratoplasty to assess the treatment as a suitable alternative to more invasive correction procedures. In addition, modifying the resident cell type as a means of improving post-treatment wound healing following LASIK was also investigated using corneal stromal stem cells. Finally, the efficiency of transepithelial riboflavin/UVA collagen cross-linking in terms of riboflavin uptake and post-treatment corneal stiffness, was evaluated.
X-ray scattering studies revealed that corneal flattening in beg chickens is related to biomechanical changes brought about by an alteration in collagen arrangement at the corneal periphery. This highlights the importance of the limbal fibril annulus in corneal shape preservation. X-ray studies also revealed that microwave keratoplasty may impact on peripheral vision by introducing spatial disruption of stromal collagen, resulting in localised corneal opacity in the treatment area. Loss of fibrillar structure and order could also have further implications for corneal biomechanics and shape. The application of human corneal stromal stem cells under LASIK-like flaps was revealed to be a promising approach for increasing flap adherence strength whilst maintaining corneal clarity. Introducing these cells in the early stages of flap-healing appears to improve the repair process, conceivably through an embryonic-like mechanism. Lastly, stress-strain and riboflavin uptake results for transepithelial riboflavin delivery during corneal cross-linking were encouraging, however refinements to the testing procedure are required to fully assess the treatment efficacy. Collectively these findings accentuate the importance of the precise stromal collagen fibril arrangement and composition for maintaining corneal transparency, shape and general functionality. All these factors must be taken into consideration when implementing novel correction procedures or modifying existing treatments for corneal defects.
Subjects/Keywords: RE Ophthalmology
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APA (6th Edition):
Morgan, S. (2014). Understanding the structural basis of corneal refractive function and its modification via novel therapeutic approaches. (Doctoral Dissertation). Cardiff University. Retrieved from http://orca.cf.ac.uk/59401/
Chicago Manual of Style (16th Edition):
Morgan, Sian. “Understanding the structural basis of corneal refractive function and its modification via novel therapeutic approaches.” 2014. Doctoral Dissertation, Cardiff University. Accessed January 19, 2021.
http://orca.cf.ac.uk/59401/.
MLA Handbook (7th Edition):
Morgan, Sian. “Understanding the structural basis of corneal refractive function and its modification via novel therapeutic approaches.” 2014. Web. 19 Jan 2021.
Vancouver:
Morgan S. Understanding the structural basis of corneal refractive function and its modification via novel therapeutic approaches. [Internet] [Doctoral dissertation]. Cardiff University; 2014. [cited 2021 Jan 19].
Available from: http://orca.cf.ac.uk/59401/.
Council of Science Editors:
Morgan S. Understanding the structural basis of corneal refractive function and its modification via novel therapeutic approaches. [Doctoral Dissertation]. Cardiff University; 2014. Available from: http://orca.cf.ac.uk/59401/
Cardiff University
20.
Hiscox, Rachel Joy.
The retina in cystic fibrosis.
Degree: PhD, 2013, Cardiff University
URL: http://orca.cf.ac.uk/59738/
► 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…
(more)
▼ 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.
Subjects/Keywords: RE Ophthalmology
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APA (6th Edition):
Hiscox, R. J. (2013). The retina in cystic fibrosis. (Doctoral Dissertation). Cardiff University. Retrieved from http://orca.cf.ac.uk/59738/
Chicago Manual of Style (16th Edition):
Hiscox, Rachel Joy. “The retina in cystic fibrosis.” 2013. Doctoral Dissertation, Cardiff University. Accessed January 19, 2021.
http://orca.cf.ac.uk/59738/.
MLA Handbook (7th Edition):
Hiscox, Rachel Joy. “The retina in cystic fibrosis.” 2013. Web. 19 Jan 2021.
Vancouver:
Hiscox RJ. The retina in cystic fibrosis. [Internet] [Doctoral dissertation]. Cardiff University; 2013. [cited 2021 Jan 19].
Available from: http://orca.cf.ac.uk/59738/.
Council of Science Editors:
Hiscox RJ. The retina in cystic fibrosis. [Doctoral Dissertation]. Cardiff University; 2013. Available from: http://orca.cf.ac.uk/59738/
Cardiff University
21.
Dunn, Matthew.
Quantifying perception and oculomotor instability in infantile nystagmus.
Degree: PhD, 2014, Cardiff University
URL: http://orca.cf.ac.uk/59972/
► The purpose of the studies described herein was to better understand the impact of involuntary eye movements on oculomotor control and perception in infantile nystagmus.…
(more)
▼ The purpose of the studies described herein was to better understand the impact of involuntary eye movements on oculomotor control and perception in infantile nystagmus. Therapeutic interventions that result in slowed nystagmus oscillations often fail to elicit significant quantifiable improvements in visual function, despite patients reporting subjective benefits. It is difficult to justify surgical or pharmacological intervention when the only outcome measures are subjective.
Objective quantification of nystagmus eye movements per se usually involves time-consuming manual marking of recordings to both calibrate and analyse data. As a result, analyses are rarely (if ever) performed in the clinical setting. Software was therefore developed to automate calibration and assessment.
Psychophysical experiments were undertaken to quantify the spatiotemporal constraints of vision in infantile nystagmus. Visual acuity was measured in the absence of retinal image motion to reveal the maximum improvement to spatial vision that might be expected if nystagmus were halted altogether. The results indicate that poor spatial vision underlies infantile nystagmus, even in cases without comorbid pathology.
Gaze acquisition time was compared to stimulus recognition time. The results indicate that infantile nystagmus does not increase visual processing time; rather, redeploying gaze takes longer.
An incidental finding revealed a temporal relationship between voluntary saccades and involuntary nystagmus quick phases. Both typically occur together, presumably to maximise efficiency and minimise saccadic suppression.
Clinical tests of gaze acquisition time must now be developed, to be used in conjunction with the software developed here, as objective outcome measures of therapeutic interventions.
Subjects/Keywords: RE Ophthalmology
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APA (6th Edition):
Dunn, M. (2014). Quantifying perception and oculomotor instability in infantile nystagmus. (Doctoral Dissertation). Cardiff University. Retrieved from http://orca.cf.ac.uk/59972/
Chicago Manual of Style (16th Edition):
Dunn, Matthew. “Quantifying perception and oculomotor instability in infantile nystagmus.” 2014. Doctoral Dissertation, Cardiff University. Accessed January 19, 2021.
http://orca.cf.ac.uk/59972/.
MLA Handbook (7th Edition):
Dunn, Matthew. “Quantifying perception and oculomotor instability in infantile nystagmus.” 2014. Web. 19 Jan 2021.
Vancouver:
Dunn M. Quantifying perception and oculomotor instability in infantile nystagmus. [Internet] [Doctoral dissertation]. Cardiff University; 2014. [cited 2021 Jan 19].
Available from: http://orca.cf.ac.uk/59972/.
Council of Science Editors:
Dunn M. Quantifying perception and oculomotor instability in infantile nystagmus. [Doctoral Dissertation]. Cardiff University; 2014. Available from: http://orca.cf.ac.uk/59972/
Cardiff University
22.
Cross, Stephen Daniel.
The role of complement in retinal ganglion cell loss in glaucoma.
Degree: PhD, 2012, Cardiff University
URL: http://orca.cf.ac.uk/60068/
► Glaucoma is an umbrella term for a number of related optic neuropathies which have the common pathology of a progressive, irreversible vision loss associated with…
(more)
▼ Glaucoma is an umbrella term for a number of related optic neuropathies which have the common pathology of a progressive, irreversible vision loss associated with atrophy of retinal ganglion cells. Together, the various forms of glaucoma constitute the second leading cause of vision loss in the developed world. Current therapies for the treatment of glaucoma focus on alleviating the primary risk factor, an elevation in intraocular pressure. These treatments are effective at mitigating the progression of vision loss however they cannot recover vision and do not completely halt vision loss, limiting their use as treatments.
To better understand the biology underlying the loss of retinal ganglion cells in glaucoma, I have examined the role of complement in retinal ganglion cell loss. Complement is a network of cross-reacting serine proteases which form part of the humoral immune system and are primarily responsible for clearance of apoptotic cells and defence against pathogens.
To understand the role played by complement in glaucoma I used an inducible model of glaucoma to establish the complement activation occurs in the glaucomatous retina. I then used the inhibitor of the classical complement cascade, C1 inhibitor to protect the dendrites and cell bodies of retinal ganglion cells and found that this protection did not prevent axonal degeneration. Using in vitro and in vivo animal models of complement deficiency I established that deficiency in complement components C3 and C6 which are further down the cascade, exacerbates damage suffered in hypertensive glaucoma.
This study adds to the existing evidence that the role of complement in central nervous system degeneration is a complex, multifactorial process, with elements of the complement system being variously protective and damaging. It does, however,
add hope to the prospect of developing a treatment for glaucomatous optic neuropathy based on manipulation of the complement system.
Subjects/Keywords: RE Ophthalmology
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APA (6th Edition):
Cross, S. D. (2012). The role of complement in retinal ganglion cell loss in glaucoma. (Doctoral Dissertation). Cardiff University. Retrieved from http://orca.cf.ac.uk/60068/
Chicago Manual of Style (16th Edition):
Cross, Stephen Daniel. “The role of complement in retinal ganglion cell loss in glaucoma.” 2012. Doctoral Dissertation, Cardiff University. Accessed January 19, 2021.
http://orca.cf.ac.uk/60068/.
MLA Handbook (7th Edition):
Cross, Stephen Daniel. “The role of complement in retinal ganglion cell loss in glaucoma.” 2012. Web. 19 Jan 2021.
Vancouver:
Cross SD. The role of complement in retinal ganglion cell loss in glaucoma. [Internet] [Doctoral dissertation]. Cardiff University; 2012. [cited 2021 Jan 19].
Available from: http://orca.cf.ac.uk/60068/.
Council of Science Editors:
Cross SD. The role of complement in retinal ganglion cell loss in glaucoma. [Doctoral Dissertation]. Cardiff University; 2012. Available from: http://orca.cf.ac.uk/60068/
Cardiff University
23.
Aljarudi, Saleh.
Some long-term outcomes of visual dysfunction arising from vigabatrin ocular toxicity.
Degree: PhD, 2014, Cardiff University
URL: http://orca.cf.ac.uk/65973/
► The purpose of this thesis was to assess long-term outcomes of the visual dysfunction arising from the ocular toxicity associated with the anti-epileptic drug vigabatrin…
(more)
▼ The purpose of this thesis was to assess long-term outcomes of the visual dysfunction arising from the ocular toxicity associated with the anti-epileptic drug vigabatrin (VGB).
The risk of vigabatrin-associated visual field loss (VAVFL) with increasing exposure to VGB was modelled from retrospectively collected data from a cohort of 147 individuals (median exposure 7.9 years; IQR 3.6, 11.0). The modelled frequency of VAVFL increased with increasing exposure and plateaued at 75-80% after approximately 6 years duration and 5kg cumulative dose.
The relationship between the numbers of retinal ganglion cell soma and axons, derived by standard automated perimetry and time-domain optical coherence tomography (TDOCT), respectively, was evaluated in 24 individuals with VAVFL and in 16 exposed to vigabatrin but with normal fields (VGBN). A strong linear association was present between the two outcomes, which was suggestive of an optic neuropathy, and was similar to the association for a control group of 18 individuals with open angle glaucoma.
A follow-up visual field, after a median interval of 7.0 years (IQR 6.5, 7.6) was determined in 19 individuals with VAVFL and in 8 with VGBN, after a median withdrawal from VGB of 7.1 years (IQR 5.4, 8.4). No consistent trend was noted for either a deterioration or improvement in the field.
A follow-up scan of the peripapillary retinal nerve fibre layer (RNFL) thickness, by TDOCT, after a median interval of 6.5 years (IQR 5.8, 6.9) was obtained in 13 individuals with VAVFL and in 4 with VGBN, after a median withdrawal from VGB of 8.0 years (IQR 5.3, 10.2). No consistent trend was noted for either a deterioration or improvement of the RNFL thickness.
The macular thickness was evaluated by TDOCT in 32 individuals with VAVFL and in 14 with VGBN. No difference in thickness was noted between the two groups.
Subjects/Keywords: RE Ophthalmology
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APA (6th Edition):
Aljarudi, S. (2014). Some long-term outcomes of visual dysfunction arising from vigabatrin ocular toxicity. (Doctoral Dissertation). Cardiff University. Retrieved from http://orca.cf.ac.uk/65973/
Chicago Manual of Style (16th Edition):
Aljarudi, Saleh. “Some long-term outcomes of visual dysfunction arising from vigabatrin ocular toxicity.” 2014. Doctoral Dissertation, Cardiff University. Accessed January 19, 2021.
http://orca.cf.ac.uk/65973/.
MLA Handbook (7th Edition):
Aljarudi, Saleh. “Some long-term outcomes of visual dysfunction arising from vigabatrin ocular toxicity.” 2014. Web. 19 Jan 2021.
Vancouver:
Aljarudi S. Some long-term outcomes of visual dysfunction arising from vigabatrin ocular toxicity. [Internet] [Doctoral dissertation]. Cardiff University; 2014. [cited 2021 Jan 19].
Available from: http://orca.cf.ac.uk/65973/.
Council of Science Editors:
Aljarudi S. Some long-term outcomes of visual dysfunction arising from vigabatrin ocular toxicity. [Doctoral Dissertation]. Cardiff University; 2014. Available from: http://orca.cf.ac.uk/65973/
Cardiff University
24.
Alshaghroud, Kholoud.
Aspects in the development of Dynamic Noise Perimetry.
Degree: PhD, 2014, Cardiff University
URL: http://orca.cf.ac.uk/66298/
► The purpose of this thesis was to develop further the concept of Dynamic Noise Perimetry (DNP). The influence of 4 different strengths of Gaussian filter…
(more)
▼ The purpose of this thesis was to develop further the concept of Dynamic Noise Perimetry (DNP).
The influence of 4 different strengths of Gaussian filter on the DNP stimulus edge, without and with a noise mask, was separately investigated in 15 normal individuals at three eccentricities. The DNP threshold was not affected by the filtering.
The critical check size of the noise mask was investigated in 11 normal individuals at three eccentricities for 8 different checks per cycle. The critical check size at the fovea was 4 checks per cycle and in the periphery between 2 and 4 checks per cycle.
The influence of optical defocus was investigated in 11 normal individuals at three eccentricities. For a defocus of +4.00DS, sensitivity without the noise mask declined by approximately 1dB; with the noise mask sensitivity increased by 1dB.
The original ‘Proof of Concept’ threshold algorithm, which enabled the estimation of threshold at one location in approximately 3 minutes, underwent numerous modifications. The final iteration permitted threshold estimation at 45 locations in approximately 7 minutes.
Five of the ten individuals with open angle glaucoma who had undergone DNP and standard automated perimetry (SAP) in 2007 were re-examined, using an identical protocol, after a follow-up of four years. The abnormality with DNP at baseline was present at the follow-up in all five individuals and was more severe in 3 individuals. Only 2 individuals exhibited abnormality by SAP.
The influence of the learning effect on the outcome of DNP was evaluated, in one designated eye at each of the five weekly visits, for 10 ‘young’ and 8 ‘elderly’ normal individuals naïve to perimetry. Optimum performance was essentially achieved at the third visit without and with the noise mask.
Subjects/Keywords: RE Ophthalmology
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APA (6th Edition):
Alshaghroud, K. (2014). Aspects in the development of Dynamic Noise Perimetry. (Doctoral Dissertation). Cardiff University. Retrieved from http://orca.cf.ac.uk/66298/
Chicago Manual of Style (16th Edition):
Alshaghroud, Kholoud. “Aspects in the development of Dynamic Noise Perimetry.” 2014. Doctoral Dissertation, Cardiff University. Accessed January 19, 2021.
http://orca.cf.ac.uk/66298/.
MLA Handbook (7th Edition):
Alshaghroud, Kholoud. “Aspects in the development of Dynamic Noise Perimetry.” 2014. Web. 19 Jan 2021.
Vancouver:
Alshaghroud K. Aspects in the development of Dynamic Noise Perimetry. [Internet] [Doctoral dissertation]. Cardiff University; 2014. [cited 2021 Jan 19].
Available from: http://orca.cf.ac.uk/66298/.
Council of Science Editors:
Alshaghroud K. Aspects in the development of Dynamic Noise Perimetry. [Doctoral Dissertation]. Cardiff University; 2014. Available from: http://orca.cf.ac.uk/66298/
Cardiff University
25.
McKeague, Claire.
The development of a clinical trial protocol and functional biomarkers for age-related macular degeneration.
Degree: mphil, 2014, Cardiff University
URL: http://orca.cf.ac.uk/68916/
► Age-related macular degeneration (AMD) is the leading cause of blindness amongst older adults in the developed world. With the predicted rise in the ageing population…
(more)
▼ Age-related macular degeneration (AMD) is the leading cause of blindness amongst older adults in the developed world. With the predicted rise in the ageing population over the next decades, the prevalence of this debilitating disease will simply continue to increase. The only treatments currently available are for advanced neovascular AMD. The retina is already severely compromised by this stage in disease development. Therefore, there is a pressing need to evaluate potential novel interventions that aim to prevent the development of advanced disease in people with early AMD, to prevent sight loss from occurring. Furthermore, it is necessary to develop tests that are sensitive to subtle changes in visual function in order to evaluate the efficacy of these emerging treatments.
There is a growing body of evidence to suggest that hypoxia contributes to the development of AMD. Hypoxia is most acute at night when the retinal photoreceptors are most metabolically active, due to the demands of the rod dark current. Increasing the light levels at night will cause the oxygen demand, and hence the hypoxia, to be substantially diminished. This leads to the hypothesis that providing low level night time light therapy to people with early AMD may slow disease progression by reducing hypoxia.
In order to evaluate the potential effectiveness of such an intervention, it is necessary to select appropriate outcome measures. The inherent variability of the standard test of visual function, visual acuity, renders it inappropriate for use as a primary outcome measure in proof of concept clinical trials. Therefore, the first aim of this thesis was to evaluate the diagnostic validity and repeatability of alternative functional tests that may be used as biomarkers for early macular disease.
Dark adaptation was evaluated using three stimuli, a spot of 2o radius and annuli of 7o and 12o radii, in 21 healthy adults (on two occasions) and in 11 participants with early AMD. All stimuli were found to be highly diagnostic for early AMD. The spot of 2o radius provided the best separation between groups with respect to the time constant of cone recovery (area under the ROC curve 0.91). The repeatability of chromatic and flicker thresholds were also assessed in 30 healthy adults. The coefficient of repeatability, expressed as a percentage of the mean threshold, was 17.1% for red-green chromatic thresholds, 31.1% for blue-yellow, 53.4% for 14Hz flicker thresholds, and ranged between 36.4%-53.3% for parameters of dark adaptation. A small learning effect was found for both chromatic thresholds and the 14-Hz flicker test, indicating that a control group is needed in studies of new therapeutic interventions.
The second aim of this thesis was to develop a protocol for a clinical trial that seeks to determine if low level night time light therapy can prevent the progression of early AMD. The level of retinal illuminance required to suppress the rod dark current, the maximum retinal illuminance which prevents substantial suppression of…
Subjects/Keywords: RE Ophthalmology
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APA (6th Edition):
McKeague, C. (2014). The development of a clinical trial protocol and functional biomarkers for age-related macular degeneration. (Masters Thesis). Cardiff University. Retrieved from http://orca.cf.ac.uk/68916/
Chicago Manual of Style (16th Edition):
McKeague, Claire. “The development of a clinical trial protocol and functional biomarkers for age-related macular degeneration.” 2014. Masters Thesis, Cardiff University. Accessed January 19, 2021.
http://orca.cf.ac.uk/68916/.
MLA Handbook (7th Edition):
McKeague, Claire. “The development of a clinical trial protocol and functional biomarkers for age-related macular degeneration.” 2014. Web. 19 Jan 2021.
Vancouver:
McKeague C. The development of a clinical trial protocol and functional biomarkers for age-related macular degeneration. [Internet] [Masters thesis]. Cardiff University; 2014. [cited 2021 Jan 19].
Available from: http://orca.cf.ac.uk/68916/.
Council of Science Editors:
McKeague C. The development of a clinical trial protocol and functional biomarkers for age-related macular degeneration. [Masters Thesis]. Cardiff University; 2014. Available from: http://orca.cf.ac.uk/68916/
Cardiff University
26.
Bandlitz, Stefan.
The role of the meniscus in the tear film.
Degree: PhD, 2015, Cardiff University
URL: http://orca.cf.ac.uk/73390/
► In the diagnosis of dry eye, an evaluation of tear fluid volume is an important parameter. The tear menisci hold approximately 75-90% of the overall…
(more)
▼ In the diagnosis of dry eye, an evaluation of tear fluid volume is an important parameter. The tear menisci hold approximately 75-90% of the overall tear fluid volume and serve as reservoirs, supplying tears to the pre-corneal tear film. The measurement of the anterior curvature radius of the tear meniscus (TMR) is an indicator of tear film volume and when it is performed non-invasively has been found to have good dry eye diagnostic accuracies. Optical coherence tomography and meniscometry are existing techniques that can measure TMR non-invasively. These techniques have not found wide application among clinicians, either because they are not commercially available or they are too expensive. This PhD describes a series of experiments that investigated the development, evaluation and application of a new instrument for non-invasive tear meniscus measurement. From the results of these studies, it can be concluded:
A Portable Digital Meniscometer (PDM) was developed. This consists of an application tool for the iPod-touch, a slit-lamp holder for the iPod-touch and an image analysis software for TMR calculation. A simple iPod-touch or an iPhone mounted on a commercially available digital slit-lamp can be used to project a grid of black and white lines on the tear meniscus. Using the principal of reflective meniscometry, the radius of the lower tear meniscus can be non-invasively measured. This newly developed instrument is a simple, mobile and useful device for measuring tear meniscus radius, and therefore tear volume, and is suitable for use by clinicians.
The newly developed PDM was evaluated in vitro and in vivo. It produced accurate and reliable measurements and provided similar values for the tear meniscus radius, in human studies, to the existing video-meniscometer. PDM and OCT measurements of the TMR were significantly correlated. Since with the PDM no image calibration is needed, it seems to be a quick and non-invasive technique for evaluation of tear fluid quantity. The PDM appears to measure the radius of the central section of the tear meniscus
The PDM was able to non-invasively measure alterations in TMR and TMH along the lower lid. The flatter TMR and higher TMH at the nasal and temporal locations may be caused by the LIPCOF degree of the underlying conjunctiva. To avoid any interference by LIPCOF, it is recommended that TMR and TMH be measured along the lower lid margin below the pupil centre. Furthermore, the PDM was able to usefully detect changes in TMR following the instillation of artificial tears. The difference in residence time is likely to reflect the different viscosity and Newtonian properties of these drops. An overload with a large drop may result in initial increased blink rate. Blink rate at baseline is significantly related to dry eye symptoms.
Subjects/Keywords: RE Ophthalmology
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APA (6th Edition):
Bandlitz, S. (2015). The role of the meniscus in the tear film. (Doctoral Dissertation). Cardiff University. Retrieved from http://orca.cf.ac.uk/73390/
Chicago Manual of Style (16th Edition):
Bandlitz, Stefan. “The role of the meniscus in the tear film.” 2015. Doctoral Dissertation, Cardiff University. Accessed January 19, 2021.
http://orca.cf.ac.uk/73390/.
MLA Handbook (7th Edition):
Bandlitz, Stefan. “The role of the meniscus in the tear film.” 2015. Web. 19 Jan 2021.
Vancouver:
Bandlitz S. The role of the meniscus in the tear film. [Internet] [Doctoral dissertation]. Cardiff University; 2015. [cited 2021 Jan 19].
Available from: http://orca.cf.ac.uk/73390/.
Council of Science Editors:
Bandlitz S. The role of the meniscus in the tear film. [Doctoral Dissertation]. Cardiff University; 2015. Available from: http://orca.cf.ac.uk/73390/
Cardiff University
27.
Gardner, Steven.
Studies of corneal structure and transparency.
Degree: PhD, 2015, Cardiff University
URL: http://orca.cf.ac.uk/73643/
► This thesis presents the results and conclusions of experiments designed to extend the current models for the origin of corneal transparency. The cornea is the…
(more)
▼ This thesis presents the results and conclusions of experiments designed to extend the current models for the origin of corneal transparency. The cornea is the transparent window at the front of the eye, which is responsible not only for the majority of refraction of light that enters, but also the protection against damage, infection and mechanical stress. The property of transparency is only realised by corneal and lens tissue in the human body. In the cornea, it has long been suspected to be caused by the precise arrangement of the fibrils of collagen that are contained within the central layer, the stroma, regulated by the sulphated proteoglycans (PG) that keep fibril spacing within acceptable boundaries. These models are consistent and give a complete description of the reasons for the transparency of a stroma that is entirely acellular. However, it is well known that the stroma is not acellular, and that the short-range order that is critical for transparency would necessarily be disturbed by the cells of the stroma, the keratocytes, which are at least an order of magnitude thicker than the maximum allowed range. Originally, an acellular stroma was considered to be a reasonable approximation due to the perceived sparsity of the cells, but more recent measurements have cast doubt upon this, and explanations have begun to focus on the properties of the cells themselves. One such property would be their refractive index (RI). If the cells could match their own RI to that of their surroundings then they would not scatter and hence would not cause a loss in transparency. This research attempts to measure that RI and by comparison with previously calculated values for the RI of the extra-cellular matrix, attempts to quantify the scale of the scattering that any mismatch would cause, using theoretical models based on both Mie scattering and finite-difference time-domain methods.
In addition to models of healthy corneas, this thesis also provides results and conclusions drawn from studies of pathological corneas and discussions of how the pathology, and the treatments, can cause initial losses in transparency. The first such study concerned a cornea afflicted with keratoconus, a disorder of as yet unknown origin that causes the weakening of the corneal tissue, leading to a characteristic cone-shaped cornea, which had been treated with a full penetrating keratoplasty (PK) transplant before being donated. The study was conducted using the techniques of electron microscopy and x-ray diffraction, to both qualitatively and quantitatively analyse the properties of the fibrils and their spacing. This was done on both the original sections of diseased tissue and the donated sections, in order to investigate the idea of keratoconus recurring in previously healthy donated tissue. Any such discovery could provide evidence that keratoconus is not an entirely inherited disorder. The structural properties of the observed scar, that was present as a direct result of the PK procedure that was carried out decades before, were also…
Subjects/Keywords: RE Ophthalmology
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APA (6th Edition):
Gardner, S. (2015). Studies of corneal structure and transparency. (Doctoral Dissertation). Cardiff University. Retrieved from http://orca.cf.ac.uk/73643/
Chicago Manual of Style (16th Edition):
Gardner, Steven. “Studies of corneal structure and transparency.” 2015. Doctoral Dissertation, Cardiff University. Accessed January 19, 2021.
http://orca.cf.ac.uk/73643/.
MLA Handbook (7th Edition):
Gardner, Steven. “Studies of corneal structure and transparency.” 2015. Web. 19 Jan 2021.
Vancouver:
Gardner S. Studies of corneal structure and transparency. [Internet] [Doctoral dissertation]. Cardiff University; 2015. [cited 2021 Jan 19].
Available from: http://orca.cf.ac.uk/73643/.
Council of Science Editors:
Gardner S. Studies of corneal structure and transparency. [Doctoral Dissertation]. Cardiff University; 2015. Available from: http://orca.cf.ac.uk/73643/
Cardiff University
28.
Nishimura, Sachiko.
The investigation of the thermal effect of contact lens wear.
Degree: mphil, 2015, Cardiff University
URL: http://orca.cf.ac.uk/73766/
► Since their introduction over 70 years ago, corneal contact lenses have continued to be improved in design and are safely used all over the world.…
(more)
▼ Since their introduction over 70 years ago, corneal contact lenses have continued to be improved in design and are safely used all over the world. Nevertheless, there is still some risk of infection, especially in soft contact lens (SCL) wearers. In comparison, rigid gas permeable lenses are less likely to cause a serious eye disease than SCL, including both traditional and silicone hydrogel lenses (SiHCL). Two possible reasons for this may be the difference in the tear exchange rate beneath the lens while on the eye, and the influence of lens material on the ocular surface temperature (OST) during the lens wear. This thesis investigates these two factors.
Firstly, an in vitro model of the ocular surface was developed to investigate the effect of lens thermal conductivity amongst lens types, and the effect of the existence of the tear film on any subsequent temperature change. The experiment confirmed the successful use of an infrared camera to measure OST change, and also found that the tear film and the water content of the lens were factors in the OST over a lens surface.
Secondly, the effect of the tear film on the OST was examined in human eyes. This study confirmed the in vitro study results and the importance of replenishing the lens water content and limiting tear evaporation.
Finally, the dynamic changes in OST during lens wear were recorded with different lens types. The OST was measured at the central and peripheral lens, and the conjunctiva. This is the first study to compare the effect of RGP and SCL wear on OST in the same subjects. Once again, similar results emphasising the importance of tear exchange and water content were found, but no effect from tear exchange beneath the lens was observed.
In summary, this thesis presents important findings about the influence of both the quality of the tear film and the type of contact lens on the OST. Also it demonstrated the usefulness of ocular thermography to investigate ocular surface changes during lens wear non-invasively
Subjects/Keywords: RE Ophthalmology
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APA (6th Edition):
Nishimura, S. (2015). The investigation of the thermal effect of contact lens wear. (Masters Thesis). Cardiff University. Retrieved from http://orca.cf.ac.uk/73766/
Chicago Manual of Style (16th Edition):
Nishimura, Sachiko. “The investigation of the thermal effect of contact lens wear.” 2015. Masters Thesis, Cardiff University. Accessed January 19, 2021.
http://orca.cf.ac.uk/73766/.
MLA Handbook (7th Edition):
Nishimura, Sachiko. “The investigation of the thermal effect of contact lens wear.” 2015. Web. 19 Jan 2021.
Vancouver:
Nishimura S. The investigation of the thermal effect of contact lens wear. [Internet] [Masters thesis]. Cardiff University; 2015. [cited 2021 Jan 19].
Available from: http://orca.cf.ac.uk/73766/.
Council of Science Editors:
Nishimura S. The investigation of the thermal effect of contact lens wear. [Masters Thesis]. Cardiff University; 2015. Available from: http://orca.cf.ac.uk/73766/
Cardiff University
29.
Nosch, Daniela.
Influences of stimulus characteristics and ocular surface conditions on non-invasive corneal sensitivity measurement.
Degree: PhD, 2015, Cardiff University
URL: http://orca.cf.ac.uk/73872/
► Purpose: To i) investigate the stimulus characteristics of the Belmonte OPM pneumatic aesthesiometer in vitro and in vivo; ii) explore the relationship between corneal sensitivity…
(more)
▼ Purpose: To i) investigate the stimulus characteristics of the Belmonte OPM pneumatic aesthesiometer in vitro and in vivo; ii) explore the relationship between corneal sensitivity threshold (CST), spontaneous eye blink rate (SEBR), ocular surface temperature (OST) and tear film quality, using the non-contact aesthesiometer (NCCA), and iii) investigate the relationship between heating and cooling of the ocular surface on CST (with the NCCA).
Methods: Stimulus flow rate (airflow meter), air stimulus volume (air capture) and force (weight scales) were recorded in vitro. Stimulus temperature was measured in vitro (using thermocouples) and in vivo (via a thermal infrared camera). SEBR, CST, OST, NIBUT and lipid pattern of the tear film were recorded. CST (using NCCA), OST and tear film quality were obtained at baseline, and after increasing and decreasing OST, using heated goggles or cooling gel mask, respectively, until OST baseline level was reached again. OST was recorded during stimulus presentation at CST, immediately after heating and cooling of the ocular surface.
Conclusions: Stimulus characteristics measured in vitro showed little variability and may therefore be considered as reliable. Stimulus temperature recorded in vivo showed that a change in stimulus flow rate produced a small, but statistically significant effect on OST. Consequently, this air stimulus may not be exclusively ‘mechanical’, and may provoke an additional response from temperature sensitive C fibres. A moderate correlation between corneal sensitivity and blink frequency was established, and a strong correlation between tear film quality, SEBR and OST was obtained, emphasising that ocular surface condition represents one important trigger for the initiation of a blink.
After both an increase and a decrease of OST, a greater localised OST decrease was required at CST, indicating that heating or cooling of the ocular surface may affect the nervous activity / sensitivity of cold thermoreceptors in the superficial cornea.
Subjects/Keywords: RE Ophthalmology
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APA ·
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MLA ·
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CSE |
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APA (6th Edition):
Nosch, D. (2015). Influences of stimulus characteristics and ocular surface conditions on non-invasive corneal sensitivity measurement. (Doctoral Dissertation). Cardiff University. Retrieved from http://orca.cf.ac.uk/73872/
Chicago Manual of Style (16th Edition):
Nosch, Daniela. “Influences of stimulus characteristics and ocular surface conditions on non-invasive corneal sensitivity measurement.” 2015. Doctoral Dissertation, Cardiff University. Accessed January 19, 2021.
http://orca.cf.ac.uk/73872/.
MLA Handbook (7th Edition):
Nosch, Daniela. “Influences of stimulus characteristics and ocular surface conditions on non-invasive corneal sensitivity measurement.” 2015. Web. 19 Jan 2021.
Vancouver:
Nosch D. Influences of stimulus characteristics and ocular surface conditions on non-invasive corneal sensitivity measurement. [Internet] [Doctoral dissertation]. Cardiff University; 2015. [cited 2021 Jan 19].
Available from: http://orca.cf.ac.uk/73872/.
Council of Science Editors:
Nosch D. Influences of stimulus characteristics and ocular surface conditions on non-invasive corneal sensitivity measurement. [Doctoral Dissertation]. Cardiff University; 2015. Available from: http://orca.cf.ac.uk/73872/
Cardiff University
30.
Malissova, Eleni.
Stuctural and functional progression in glaucoma: some aspects.
Degree: PhD, 2015, Cardiff University
URL: http://orca.cf.ac.uk/78319/
► This thesis explored some aspects of the relationship between structural progression of the glaucomatous optic nerve head (ONH) and functional progression of the visual field.…
(more)
▼ This thesis explored some aspects of the relationship between structural progression of the glaucomatous optic nerve head (ONH) and functional progression of the visual field.
Sixty-one individuals with a longitudinal series of ONH images were manually identified from a database of approximately 2800 individuals attending a hospital glaucoma clinic. The ONH images obtained from the various photographic sources were equalized, for each individual, in terms of ONH size.
Custom-software was designed to enable the viewing of consecutive and chronologically different ONH image-pairs under monoscopic and stereoscopic conditions, with and without sequential flicker. The efficacy, for the identification of progressive glaucomatous loss, amongst the 61 individuals, of the four viewing techniques was qualitatively evaluated by two ophthalmologists. Stereo-flicker identified the largest number of cases of progression, although little agreement was present between the two ophthalmologists.
The digital characteristics of the ONH images from 27 of the 61 individuals enabled quantitative digital stereo-planimetry. A weak positive curvilinear association was present, at baseline, between the reduction in the neuroretinal rim area and the outcomes of perimetry, including residual retinal ganglion cell (RGC) count. However, little agreement was again present between the two ophthalmologists. Little association was present with either ophthalmologist between progressive structural damage and functional damage.
A separate manual search of 1000 individuals with glaucoma archived in ‘Open eyes’ identified 112 individuals with a minimum of 5 visual field examinations over a minimum of 5 years. The outcomes at each stimulus location of the differential light sensitivity, expressed in decibels (dB), and of the residual RGC count, against time to follow-up, were compared using univariate linear regression analysis. In general, residual RGC count identified progression, in terms of a greater statistical significance and/ or of more stimulus locations, at an earlier stage of the disease than sensitivity expressed in dB.
Subjects/Keywords: RE Ophthalmology
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APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
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Manager
APA (6th Edition):
Malissova, E. (2015). Stuctural and functional progression in glaucoma: some aspects. (Doctoral Dissertation). Cardiff University. Retrieved from http://orca.cf.ac.uk/78319/
Chicago Manual of Style (16th Edition):
Malissova, Eleni. “Stuctural and functional progression in glaucoma: some aspects.” 2015. Doctoral Dissertation, Cardiff University. Accessed January 19, 2021.
http://orca.cf.ac.uk/78319/.
MLA Handbook (7th Edition):
Malissova, Eleni. “Stuctural and functional progression in glaucoma: some aspects.” 2015. Web. 19 Jan 2021.
Vancouver:
Malissova E. Stuctural and functional progression in glaucoma: some aspects. [Internet] [Doctoral dissertation]. Cardiff University; 2015. [cited 2021 Jan 19].
Available from: http://orca.cf.ac.uk/78319/.
Council of Science Editors:
Malissova E. Stuctural and functional progression in glaucoma: some aspects. [Doctoral Dissertation]. Cardiff University; 2015. Available from: http://orca.cf.ac.uk/78319/
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