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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
281

Effect of metabolic insult on amino acids in the ciliary epithelium, lens, and retina

Hu, Guo Min January 2007 (has links)
Ischaemic insult deprives ocular tissue of oxygen and essential metabolites leading to anatomical and functional changes. One way to gauge the effect of ocular ischaemia is to determine changes in amino acids likely to be modified due to the intricate interrelationship between cellular metabolism and these compounds. Such an approach, using quantitative silver-intensified immunogold detection of a range of immunoglobulins, can provide a metabolic profile of cells (metabolome). Despite the known alterations in the ciliary epithelium and lens function secondary to ocular ischaemia, little is know about the metabolic profile in both normal ocular tissue and in ocular tissue exposed to metabolic insult. The major goal of this thesis was to investigate the metabolome of the ciliary epithelium and lens under normal and ischaemic conditions, in parallel to that of the retina, with complete spatial and single cell resolution. The results showed that a glutamate/glutamine cycle exists between the ciliary epithelium and lens, in analogy to the metabolic relationship between neurons and glia in the retina. with the localisation of glutamine synthetase and glutamate transporters, amino acids including glutamate and glutamine accumulate in the ciliary epithelium for secretion, so that lens amino acid levels can be sustained. Experimental manipulations reported in this thesis include enzyme inhibition and exposure to acute ischaemia, both leading to fluctuations of the amino acid levels/distributions in the ciliary epithelium and retina, and changes in amino acids associated with cellular metabolism. In the ischaemia/reperfusion experiments, despite recovery of anatomical features, there were persistent metabolic changes in the ciliary epithelium after four days reperfusion, which results in lower amino acids both in the ciliary epithelium and lens. Further, studies of glutamate transporters led to the discovery of a unique mechanism of glutamate release involving the cystine-glutamate transporter at the photoreceptor ribbon complex. In conclusion, the results offer a parsimonious explanation for the common association of altered ciliary body function and cataract secondary to ischaemic insult and provide evidence for highly conserved amino acid metabolic pathways within ocular tissues. / Whole document restricted, but available by request, use the feedback form to request access.
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282

The Role of the crystalline lens in ametropia

Scott, Rolene January 1993 (has links)
When examining the dimensions of the crystalline lens, it is found that some may vary with different types of refractive error. The effects of several of these variations on refractive error are investigated in this thesis. To examine whether lens thickness was significantly different in youth-onset myopes compared with emmetropes, a structural model was developed and tested. No substantial difference was found between the two groups. In both groups of eyes, increased lens thickness was found to contribute significantly to the refractive state of the eye; a thicker lens effectively being a stronger lens. The crystalline lens may play a different role in early adult-onset myopia which develops after normal growth has ceased compared to its role in youth-onset myopia. Cross-sectional data from early adult-onset myopes, youth-onset myopes and emmetropes were evaluated to determine whether lens thickness differed among the refractive error groups. No significant differences were found. However, some early adult-onset myopes and youth-onset myopes were re-evaluated three years after the initial data were collected and a significant increase in mean lens thickness was, found in the group of early adult-onset, myopes. No significant mean lens thickness increase occurred in the group of youth-onset myopes. To evaluate further the contribution of the crystalline lens dimensions to the refractive state of the eye, radii of curvature and. lens thicknesses of a group of anisometropes were examined. Radii were found not to be consistently flatter or steeper in the relatively, more myropic eye compared with the relatively less myopic eye and there was also no significant difference between mean lens thickness of the relatively more myopic eye compared to mean lens thickness of the relatively less, myopic eye. Crystalline lens thickness and radii of curvature were therefore found to play only a minor role in refractive error development, Deeper vitreous chambers and steeper corneal curvatures were found to be the major contributors to myopia.
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283

Effect of metabolic insult on amino acids in the ciliary epithelium, lens, and retina

Hu, Guo Min January 2007 (has links)
Ischaemic insult deprives ocular tissue of oxygen and essential metabolites leading to anatomical and functional changes. One way to gauge the effect of ocular ischaemia is to determine changes in amino acids likely to be modified due to the intricate interrelationship between cellular metabolism and these compounds. Such an approach, using quantitative silver-intensified immunogold detection of a range of immunoglobulins, can provide a metabolic profile of cells (metabolome). Despite the known alterations in the ciliary epithelium and lens function secondary to ocular ischaemia, little is know about the metabolic profile in both normal ocular tissue and in ocular tissue exposed to metabolic insult. The major goal of this thesis was to investigate the metabolome of the ciliary epithelium and lens under normal and ischaemic conditions, in parallel to that of the retina, with complete spatial and single cell resolution. The results showed that a glutamate/glutamine cycle exists between the ciliary epithelium and lens, in analogy to the metabolic relationship between neurons and glia in the retina. with the localisation of glutamine synthetase and glutamate transporters, amino acids including glutamate and glutamine accumulate in the ciliary epithelium for secretion, so that lens amino acid levels can be sustained. Experimental manipulations reported in this thesis include enzyme inhibition and exposure to acute ischaemia, both leading to fluctuations of the amino acid levels/distributions in the ciliary epithelium and retina, and changes in amino acids associated with cellular metabolism. In the ischaemia/reperfusion experiments, despite recovery of anatomical features, there were persistent metabolic changes in the ciliary epithelium after four days reperfusion, which results in lower amino acids both in the ciliary epithelium and lens. Further, studies of glutamate transporters led to the discovery of a unique mechanism of glutamate release involving the cystine-glutamate transporter at the photoreceptor ribbon complex. In conclusion, the results offer a parsimonious explanation for the common association of altered ciliary body function and cataract secondary to ischaemic insult and provide evidence for highly conserved amino acid metabolic pathways within ocular tissues. / Whole document restricted, but available by request, use the feedback form to request access.
Read more
284

The Role of the crystalline lens in ametropia

Scott, Rolene January 1993 (has links)
When examining the dimensions of the crystalline lens, it is found that some may vary with different types of refractive error. The effects of several of these variations on refractive error are investigated in this thesis. To examine whether lens thickness was significantly different in youth-onset myopes compared with emmetropes, a structural model was developed and tested. No substantial difference was found between the two groups. In both groups of eyes, increased lens thickness was found to contribute significantly to the refractive state of the eye; a thicker lens effectively being a stronger lens. The crystalline lens may play a different role in early adult-onset myopia which develops after normal growth has ceased compared to its role in youth-onset myopia. Cross-sectional data from early adult-onset myopes, youth-onset myopes and emmetropes were evaluated to determine whether lens thickness differed among the refractive error groups. No significant differences were found. However, some early adult-onset myopes and youth-onset myopes were re-evaluated three years after the initial data were collected and a significant increase in mean lens thickness was, found in the group of early adult-onset, myopes. No significant mean lens thickness increase occurred in the group of youth-onset myopes. To evaluate further the contribution of the crystalline lens dimensions to the refractive state of the eye, radii of curvature and. lens thicknesses of a group of anisometropes were examined. Radii were found not to be consistently flatter or steeper in the relatively, more myropic eye compared with the relatively less myopic eye and there was also no significant difference between mean lens thickness of the relatively more myopic eye compared to mean lens thickness of the relatively less, myopic eye. Crystalline lens thickness and radii of curvature were therefore found to play only a minor role in refractive error development, Deeper vitreous chambers and steeper corneal curvatures were found to be the major contributors to myopia.
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285

Effect of metabolic insult on amino acids in the ciliary epithelium, lens, and retina

Hu, Guo Min January 2007 (has links)
Ischaemic insult deprives ocular tissue of oxygen and essential metabolites leading to anatomical and functional changes. One way to gauge the effect of ocular ischaemia is to determine changes in amino acids likely to be modified due to the intricate interrelationship between cellular metabolism and these compounds. Such an approach, using quantitative silver-intensified immunogold detection of a range of immunoglobulins, can provide a metabolic profile of cells (metabolome). Despite the known alterations in the ciliary epithelium and lens function secondary to ocular ischaemia, little is know about the metabolic profile in both normal ocular tissue and in ocular tissue exposed to metabolic insult. The major goal of this thesis was to investigate the metabolome of the ciliary epithelium and lens under normal and ischaemic conditions, in parallel to that of the retina, with complete spatial and single cell resolution. The results showed that a glutamate/glutamine cycle exists between the ciliary epithelium and lens, in analogy to the metabolic relationship between neurons and glia in the retina. with the localisation of glutamine synthetase and glutamate transporters, amino acids including glutamate and glutamine accumulate in the ciliary epithelium for secretion, so that lens amino acid levels can be sustained. Experimental manipulations reported in this thesis include enzyme inhibition and exposure to acute ischaemia, both leading to fluctuations of the amino acid levels/distributions in the ciliary epithelium and retina, and changes in amino acids associated with cellular metabolism. In the ischaemia/reperfusion experiments, despite recovery of anatomical features, there were persistent metabolic changes in the ciliary epithelium after four days reperfusion, which results in lower amino acids both in the ciliary epithelium and lens. Further, studies of glutamate transporters led to the discovery of a unique mechanism of glutamate release involving the cystine-glutamate transporter at the photoreceptor ribbon complex. In conclusion, the results offer a parsimonious explanation for the common association of altered ciliary body function and cataract secondary to ischaemic insult and provide evidence for highly conserved amino acid metabolic pathways within ocular tissues. / Whole document restricted, but available by request, use the feedback form to request access.
Read more
286

The Role of the crystalline lens in ametropia

Scott, Rolene January 1993 (has links)
When examining the dimensions of the crystalline lens, it is found that some may vary with different types of refractive error. The effects of several of these variations on refractive error are investigated in this thesis. To examine whether lens thickness was significantly different in youth-onset myopes compared with emmetropes, a structural model was developed and tested. No substantial difference was found between the two groups. In both groups of eyes, increased lens thickness was found to contribute significantly to the refractive state of the eye; a thicker lens effectively being a stronger lens. The crystalline lens may play a different role in early adult-onset myopia which develops after normal growth has ceased compared to its role in youth-onset myopia. Cross-sectional data from early adult-onset myopes, youth-onset myopes and emmetropes were evaluated to determine whether lens thickness differed among the refractive error groups. No significant differences were found. However, some early adult-onset myopes and youth-onset myopes were re-evaluated three years after the initial data were collected and a significant increase in mean lens thickness was, found in the group of early adult-onset, myopes. No significant mean lens thickness increase occurred in the group of youth-onset myopes. To evaluate further the contribution of the crystalline lens dimensions to the refractive state of the eye, radii of curvature and. lens thicknesses of a group of anisometropes were examined. Radii were found not to be consistently flatter or steeper in the relatively, more myropic eye compared with the relatively less myopic eye and there was also no significant difference between mean lens thickness of the relatively more myopic eye compared to mean lens thickness of the relatively less, myopic eye. Crystalline lens thickness and radii of curvature were therefore found to play only a minor role in refractive error development, Deeper vitreous chambers and steeper corneal curvatures were found to be the major contributors to myopia.
Read more
287

Effect of metabolic insult on amino acids in the ciliary epithelium, lens, and retina

Hu, Guo Min January 2007 (has links)
Ischaemic insult deprives ocular tissue of oxygen and essential metabolites leading to anatomical and functional changes. One way to gauge the effect of ocular ischaemia is to determine changes in amino acids likely to be modified due to the intricate interrelationship between cellular metabolism and these compounds. Such an approach, using quantitative silver-intensified immunogold detection of a range of immunoglobulins, can provide a metabolic profile of cells (metabolome). Despite the known alterations in the ciliary epithelium and lens function secondary to ocular ischaemia, little is know about the metabolic profile in both normal ocular tissue and in ocular tissue exposed to metabolic insult. The major goal of this thesis was to investigate the metabolome of the ciliary epithelium and lens under normal and ischaemic conditions, in parallel to that of the retina, with complete spatial and single cell resolution. The results showed that a glutamate/glutamine cycle exists between the ciliary epithelium and lens, in analogy to the metabolic relationship between neurons and glia in the retina. with the localisation of glutamine synthetase and glutamate transporters, amino acids including glutamate and glutamine accumulate in the ciliary epithelium for secretion, so that lens amino acid levels can be sustained. Experimental manipulations reported in this thesis include enzyme inhibition and exposure to acute ischaemia, both leading to fluctuations of the amino acid levels/distributions in the ciliary epithelium and retina, and changes in amino acids associated with cellular metabolism. In the ischaemia/reperfusion experiments, despite recovery of anatomical features, there were persistent metabolic changes in the ciliary epithelium after four days reperfusion, which results in lower amino acids both in the ciliary epithelium and lens. Further, studies of glutamate transporters led to the discovery of a unique mechanism of glutamate release involving the cystine-glutamate transporter at the photoreceptor ribbon complex. In conclusion, the results offer a parsimonious explanation for the common association of altered ciliary body function and cataract secondary to ischaemic insult and provide evidence for highly conserved amino acid metabolic pathways within ocular tissues. / Whole document restricted, but available by request, use the feedback form to request access.
Read more
288

The Role of the crystalline lens in ametropia

Scott, Rolene January 1993 (has links)
When examining the dimensions of the crystalline lens, it is found that some may vary with different types of refractive error. The effects of several of these variations on refractive error are investigated in this thesis. To examine whether lens thickness was significantly different in youth-onset myopes compared with emmetropes, a structural model was developed and tested. No substantial difference was found between the two groups. In both groups of eyes, increased lens thickness was found to contribute significantly to the refractive state of the eye; a thicker lens effectively being a stronger lens. The crystalline lens may play a different role in early adult-onset myopia which develops after normal growth has ceased compared to its role in youth-onset myopia. Cross-sectional data from early adult-onset myopes, youth-onset myopes and emmetropes were evaluated to determine whether lens thickness differed among the refractive error groups. No significant differences were found. However, some early adult-onset myopes and youth-onset myopes were re-evaluated three years after the initial data were collected and a significant increase in mean lens thickness was, found in the group of early adult-onset, myopes. No significant mean lens thickness increase occurred in the group of youth-onset myopes. To evaluate further the contribution of the crystalline lens dimensions to the refractive state of the eye, radii of curvature and. lens thicknesses of a group of anisometropes were examined. Radii were found not to be consistently flatter or steeper in the relatively, more myropic eye compared with the relatively less myopic eye and there was also no significant difference between mean lens thickness of the relatively more myopic eye compared to mean lens thickness of the relatively less, myopic eye. Crystalline lens thickness and radii of curvature were therefore found to play only a minor role in refractive error development, Deeper vitreous chambers and steeper corneal curvatures were found to be the major contributors to myopia.
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289

Hur miljövänlig är dagens optikerbutik, och hur miljövänlig kan den bli?

Mattsson, Carina January 2008 (has links)
<p>SUMMARY</p><p>Environmental issues are currently a hot topic of debate. Studies within the optics branch have not specifically been conducted previously, so the aim of this study was to determine the extent of environmental-awareness specifically within this branch.</p><p>A survey, consisting of questions relating to environmental issues, was distributed to 100 randomly-selected opticians in Sweden. Of these 100 surveys, 64 were returned and showed a varied branch-engagement for environmental issues.</p><p>Results of this survey showed that opticians were best in sorting newspapers, magazines, other paper and hazardous waste. Metal and rigid plastic were not sorted to any larger extent.</p><p>Choosing environmentally-safe products was not so popular and only six stores always do this. 25 shops turn off electrical machines and equipment over night; while the majority of the remaining stores leave the machines on during the night.</p><p>27 stores did not know if their electrical company provided “green electricity”.</p><p>Results showed that there is a lot of work to be done in making the stores more environmentally friendly. Changes do not have to be great, however all changes can help protect the environment and even result in economic benefits for a practice.</p><p>• Choose electrical-companies that provide “green electricity”</p><p>• Sort garbage better</p><p>• Create an environmental policy in the practice</p><p>• Discuss environmental issues with suppliers</p><p>• Request environmentally-safe products from suppliers</p><p>• Choose environmentally safe products as much as possible</p><p>• Try to think about the environment when travelling or commuting</p><p>• Turn off all electrical machines when not in use</p><p>• Don’t waste water, electricity, chemicals, paper etc.</p><p>• Get information and get environmentally active</p> / <p>Abstrakt</p><p>Miljöarbete är i full gång i hela världen och det är ett mycket aktuellt och viktigt ämne. Därför kom funderingar över hur miljöarbetet ser ut i optikbranschen, och om man kunde göra några förbättringar i det. För att ta reda på det skapades en enkät som skickades ut till 100 slumpmässigt utvalda optikerbutiker i Sverige. 64 enkäter besvarades och visade på ett blandat miljöengagemang.</p><p>Enkätsvaren visade att butikerna var bäst på att källsortera tidningar, annat papper och miljöfarligt avfall, medan de var sämst på att sortera metall och hårdplast. Att alltid välja miljövänliga produkter var inte så vanligt, bara 6 butiker väljer alltid det. Att stänga av de elektriska apparaterna till natten var det 25 butiker som gjorde medan 37 stycken låter apparaterna stå på. 27 stycken butiker visste inte om de anlitade ett elbolag som sålde ”grön el”. 53 butiker tror att de kan påverka miljön till det bättre genom att ”dra sitt strå till stacken”.</p><p>Enkätsvaren visar dessutom på att det finns en del att jobba med för att göra butikerna miljövänligare. Det behöver inte vara särskilt stora förändringar för att miljöarbetet ska skjuta fart. Vissa miljöinsatser kan faktiskt spara pengar.</p><p>2008:O20</p>
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290

Refractive and keratometric measurements: departures from and transformations towards normality.

Blackie, Caroline Adrienne 11 February 2014 (has links)
M.Phil. (Optometry) / Different representations of dioptric power and their relative coordinate systems are summarised. The transition matrices required to switch from one coordinate system to another are provided. Three sets of data are analysed; a sample of 205 refractions, a sample of 205 keratometric readings and a sample of 790 autorefractive excesses of 790 autorefractions over 790 subjective refractions. Brief mention is made of emmetropisation. In the event that such a driving force exists, the possible effects on the distributional characteristics of refractive error are noted. Normality and the assessment thereof are discussed qualitatively and quantitatively. The univariate marginal and multivariate joint distributions .of the samples are examined using the coordinate system introduced by Deal and Toop (1993): their vector is represented by d=(d 1 d 2 d3)~ Departure from normality is determined in three ways; assessment of the linearity of the chi-square probability plots, measures of skewness and measures of kurtosis. Marginal normal probability plots are included for completeness. The statistical procedures and some of the theory involved in the implementation of these techniques are described briefly to assist in the interpretation of the distribution analysis. Marginal transformations are employed to improve the normality of the marginal distributions in an attempt to reduce the multivariate departure from normality. Power transformations and shifted power transformations are described and applied to the data.
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