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Tesi sul tema "Retinopathly"
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1
Mahon, Gerald J. "Studies on chloroquine retinopathy". Thesis, Queen's University Belfast, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.388235.
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2
Loukovaara, Sirpa. "Diabetic retinopathy and pregnancy". Helsinki : University of Helsinki, 2003. http://ethesis.helsinki.fi/julkaisut/laa/kliin/vk/loukovaara/.
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3
Teng, Thomas Bart. "Vessel identification in diabetic retinopathy". Thesis, Bournemouth University, 2003. http://eprints.bournemouth.ac.uk/441/.
Testo completoAbstract (sommario):
Diabetic retinopathy is the single largest cause of sight loss and blindness in 18 to 65 year olds. Screening programs for the estimated one to six per- cent of the diabetic population have been demonstrated to be cost and sight saving, howeverthere are insufficient screening resources. Automatic screen-ing systems may help solve this resource short fall. This thesis reports on research into an aspect of automatic grading of diabetic retinopathy; namely the identification of the retinal blood vessels in fundus photographs. It de-velops two vessels segmentation strategies and assess their accuracies. A literature review of retinal vascular segmentation found few results, and indicated a need for further development. The two methods for vessel segmentation were investigated in this thesis are based on mathematical morphology and neural networks. Both methodologies are verified on independently labeled data from two institutions and results are presented that characterisethe trade off betweenthe ability to identify vesseland non-vessels data. These results are based on thirty five images with their retinal vessels labeled. Of these images over half had significant pathology and or image acquisition artifacts. The morphological segmentation used ten images from one dataset for development. The remaining images of this dataset and the entire set of 20 images from the seconddataset were then used to prospectively verify generaliastion. For the neural approach, the imageswere pooled and 26 randomly chosenimageswere usedin training whilst 9 were reserved for prospective validation. Assuming equal importance, or cost, for vessel and non-vessel classifications, the following results were obtained; using mathematical morphology 84% correct classification of vascular and non-vascular pixels was obtained in the first dataset. This increased to 89% correct for the second dataset. Using the pooled data the neural approach achieved 88% correct identification accuracy. The spread of accuracies observed varied. It was highest in the small initial dataset with 16 and 10 percent standard deviation in vascular and non-vascular cases respectively. The lowest variability was observed in the neural classification, with a standard deviation of 5% for both accuracies. The less tangible outcomes of the research raises the issueof the selection and subsequent distribution of the patterns for neural network training. Unfortunately this indication would require further labeling of precisely those cases that were felt to be the most difficult. I.e. the small vessels and border conditions between pathology and the retina. The more concrete, evidence based conclusions,characterise both the neural and the morphological methods over a range of operating points. Many of these operating points are comparable to the few results presented in the literature. The advantage of the author's approach lies in the neural method's consistent as well as accurate vascular classification.
4
Hillman, Nicola Jane. "Hypertension and experimental diabetic retinopathy". Thesis, University of Southampton, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.241987.
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5
Penishkevich, Ya I. "Pathophysiological mechanisms of diabetic retinopathy". Thesis, БДМУ, 2021. http://dspace.bsmu.edu.ua:8080/xmlui/handle/123456789/18637.
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6
Mohamed, Shaheeda. "Efficacy of intravitreal triamcinolone in diabetic macular edema". Thesis, View the Table of Contents & Abstract, 2007. http://sunzi.lib.hku.hk/hkuto/record/B38479114.
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7
Heintz, Emelie. "Health economic aspects of diabetic retinopathy". Doctoral thesis, Linköpings universitet, Utvärdering och hälsoekonomi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-76283.
Testo completoAbstract (sommario):
To ensure that the resources of the health care sector are used effectively, new technologies need to be evaluated before implementation to examine if they generate health outcomes at an acceptable cost. This information can be collected by performing health economic evaluations in which the costs and health outcomes of different technologies are compared. To estimate the effect on health care budgets, there is also a need for information about the prevalence of the specific disease. Health outcomes in health economic evaluations are often measured in quality-adjusted life years (QALYs), which are calculated by multiplying the remaining life years after an intervention by a weight representing the health-related quality of life (HRQoL) during those years. This thesis aims to provide deeper knowledge of the health economic aspects of diabetic retinopathy (DR), an eye complication that affects patients with diabetes and may in the worst case lead to blindness. The focus is on three empirical and two methodological health economic research questions. The empirical research areas cover prevalence, costs, and HRQoL related to patients with DR. The methodological research questions explore the performance of different methods for estimation of QALY weights. This is of interest since it has been argued that the most common methods for estimating QALY weights may not capture all relevant vision-related aspects of quality of life. The analyses comprehend the validity of different methods for estimating QALY weights among patients with DR and if the results of one of the specific methods for estimating QALY weights, the time trade-off (TTO) exercise, are affected by patients’ subjective life expectancy (SLE). The empirical results demonstrate that DR is seen in approximately 40% and 30% of patients with type I and type II diabetes respectively, indicating that the prevalence of DR has decreased in both of these patient groups. Healthcare costs vary considerably between different severity levels of the disease, being estimated at €26, €257, €216, and €433 per patient per year for background retinopathy, proliferative diabetic retinopathy (PDR), diabetic macular oedema (DMO), and PDR combined with DMO respectively. Blindness due to DR is associated with an increased use of transportation services, caregiving services, and assistive technologies as well as productivity losses. This suggests that preventing the progression of DR may lower healthcare costs. Patients with vision impairment due to DR have lowered HRQoL in various dimensions, but the diagnosis of DR in itself has only a limited effect on HRQoL. The results on the methodological research questions show that different methods for estimating QALY weights seem to give different results. In comparison to EQ-5D, the Health Utilities Index Mark 3 (HUI-3) is the most sensitive method for detecting differences in QALY weights due to DR, and if decisions are to be made based on values from the general public, it can be recommended for use in cost-utility analyses of interventions directed at DR. Neither of the direct methods, TTO and the visual analogue scale, seems to be sensitive to differences in visual function, and more research is needed concerning the role of vision in people’s responses to the TTO exercises. In TTO exercises with time frames based on actuarial life expectancy, the patients’ SLE has an effect on their willingness to trade off years for full health. Thus, applying time frames deviating from patients’ SLE may result in biased QALY weights. Such bias may appear stronger within patient populations than within the general public. In conclusion, this thesis offers estimates for prevalence, costs, and QALY weights that can be used in economic evaluations of interventions directed at DR and as benchmarks for future DR research in order to follow up consequences of changes in diabetes care. In addition, it demonstrates that the choice of method for estimating QALY weights may have an impact on whether an intervention is considered cost-effective.
8
Brooks, Roger Audley. "Fibroblast growth factor and diabetic retinopathy". Thesis, Imperial College London, 1991. http://hdl.handle.net/10044/1/46684.
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9
van, Wijngaarden Peter, e petervanwijn@yahoo com au. "Heritable influences in oxygen-induced retinopathy". Flinders University. Medicine, 2006. http://catalogue.flinders.edu.au./local/adt/public/adt-SFU20060824.211102.
Testo completoAbstract (sommario):
Retinopathy of prematurity, a disease characterised by aberrant retinal vascular development in premature neonates, is a leading cause of blindness and visual impairment in childhood. This work sought to examine differences in the susceptibility of inbred rat strains to oxygen-induced retinopathy, a model of human retinopathy of prematurity. The overriding aim was to identify genetic factors in rats that might be generalisable to humans.
Newborn rats of six different strains were exposed to alternating cycles of hyperoxia and relative hypoxia for fourteen days. Rats were removed to room air and killed for analysis immediately, to assess oxygen-induced retinal vascular attenuation, or four days later to evaluate the extent of hypoxia-induced vasoproliferation. Whole flat-mounted retinae were stained with fluorophore conjugated isolectin GS-IB4, and measurement of vascular area was conducted using fluorescence microscopy and video-image analysis. A hierarchy of susceptibility to the inhibitory effects of cyclic hyperoxia and relative hypoxia on postnatal retinal vascularization was identified for the rat strains studied. Susceptibility to vascular attenuation was predictive of the subsequent risk of vascular morphological abnormalities. Cross-breeding experiments between susceptible and resistant strains demonstrated that the susceptible phenotype was dominantly inherited in an autosomal fashion. These studies confirmed an association between ocular pigmentation and retinopathy risk, however the finding of differential susceptibility amongst albino rat strains implicated factors in addition to those associated with ocular pigmentation.
Quantitative real-time reverse transcription-polymerase chain reaction was used to compare the retinal expression of angiogenic factor genes in susceptible and resistant strains with the aim of identifying a genetic basis for the strain difference. Eight angiogenic factor genes were selected for study: vascular endothelial growth factor (VEGF); VEGF receptor 2; angiopoietin 2; Tie2; pigment epithelium-derived factor; erythropoietin; cyclooxygenase-2 and insulin-like growth factor-1. The most notable difference between strains was the expression of vascular endothelial growth factor (VEGF) during the cyclic hyperoxia exposure period - higher VEGF expression was associated with relative resistance to retinopathy. Other differences in retinal angiogenic factor gene expression between strains, such as higher expression of VEGF receptor 2 and angiopoietin 2 in resistant strains, appeared to be secondary to those in VEGF. Following cyclic hyperoxia, the expression pattern of angiogenic factor genes changed - messenger RNA levels of hypoxia-induced genes, including VEGF, VEGF receptor 2, angiopoietin 2 and erythropoietin, were significantly higher in those strains with larger avascular areas, than in those strains that were relatively resistant to retinopathy. These findings provide firm evidence for hereditary risk factors for oxygen-induced retinopathy in the rat. Differences in the regulatory effects of oxygen on VEGF expression appear to be central to the risk of retinopathy. The potential relevance of these hereditary factors is discussed in the context of the human disease.
10
Cox, Orla T. "Vascular cell death in diabetic retinopathy". Thesis, Queen's University Belfast, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343079.
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CAUJOLLE, CATHERINE. "Retinopathie diabetique et grossesse". Nice, 1994. http://www.theses.fr/1994NICE6567.
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12
MARTINEZ, PASCALE. "Retinopathie diabetique et microalbuminurie". Toulouse 3, 1988. http://www.theses.fr/1988TOU31046.
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13
Lhussiez, Vincent. "Caractérisation des effets ophtalmiques du syndrome de Cohen chez des souris VPS13B-/- et identification des mécanismes moléculaires impliqué dans la pathogenèse". Thesis, Bourgogne Franche-Comté, 2020. http://www.theses.fr/2020UBFCK054.
Testo completoAbstract (sommario):
Le Syndrome de Cohen (SC)(OMIM 216550) est une maladie autosomique récessive rare due à des variations dans le gène codant pour la protéine de tri vacuolaire 13B (VPS13B ou COH1). Les patients possèdent des caractéristiques cliniques typiques : une dysmorphie faciale, une neutropénie, une répartition anormale des graisses au niveau du tronc, une microcéphalie associée à une déficience intellectuelle, une myopie et des atteintes rétiniennes. Mon projet de thèse a eu pour but de caractériser le phénotype ophtalmologique du modèle murin du SC (Vps13bEx3/Ex3) afin de déterminer les mécanismes moléculaires impliqués dans la mise en place de la rétinopathie du SC.Nous avons montré que les souris Vps13bEx3/Ex3 développent une cataracte entre 2 et 3 mois d’âge, avec une désorganisation des cellules fibreuses du cristallin et leur différenciation en cellules mésenchymateuses. À un stade plus avancé, la membrane externe du cristallin est rompue et les parties corticale et nucléaire du cristallin se séparent. Après l’apparition de la cataracte, la rétine présente des déformations se caractérisant par un amincissement et une déformation de ses différentes couches pouvant engendrer des plis rétiniens de 50 à 500µm de long. Il y a également une forte prolifération des cellules microgliales ainsi qu’une astrogliose. La découverte de la cataracte dans notre modèle a conduit à une revue exhaustive de la littérature permettant de mettre en évidence que la cataracte est présente chez 85% des patients à 40 ans et sans lien avec la rétinopathie.Nous avons ensuite montré une modification du phénotype oculaire en présence de la mutation Crb1Rd8. Crb1 est une protéine transmembranaire dont la variation Rd8 entraine une désorganisation de la rétine. Nous avons créé des cohortes de tous les génotypes Vps13b/Cr1 possibles. Nos analyses préliminaires montrent une dystrophie rétinienne précoce chez les souris Vps13bEx3/Ex3 Crb1Rd8/+, suggérant que Vps13b pourrait être un gène modificateur de Crb1. Les mécanismes moléculaires pouvant conduire à l’apparition de la rétinopathie du SC ont été étudiés sur des souris Vps13bEx3/Ex3Crb1+/+. La structure de la rétine et ses différentes populations cellulaires ont été étudiées mais n’ont pas révélé d’anomalies avant l’apparition de la cataracte. Cependant l’étude des mécanismes inflammatoires a montré une augmentation de la sensibilité à IL6 dans la rétine de notre modèle. Ce mécanisme pourrait être impliqué dans la mise en place de la rétinopathie. Le phénotype oculaire étant fortement diminué chez les souris Vps13bEx3/Ex3 Crb1+/+, l’impact des facteurs environnementaux, et en particulier la lumière, a également été étudié et montre que soumises à de fortes intensités lumineuses, les souris développent des rétinopathies.En parallèle, nous avons étudié les caractéristiques ophtalmologiques des patients de notre cohorte principalement à l’aide d’OCT. Cette étude révèle (i) que l’œdème maculaire est un symptôme fréquent du SC qui reste relativement stable dans le temps et (ii) que l’apparition de la rétinopathie est indépendante de celle de la cataracte.Ainsi mes travaux de doctorat ont permis de caractériser les atteintes ophtalmiques de notre modèle murin Vps13bEx3/Ex3. L’étude des mécanismes cellulaires impliqués dans la rétinopathie et la cataracte du SC doit être approfondie afin de permettre de trouver une cible thérapeutique ou des stratégies de prévention pour ces atteintes ophtalmiquesCohen Syndrome (CS) is a rare autosomal recessive disease caused by variations in the gene coding for the vacuolar tri-vacuolar protein 13B (VPS13B or COH1). CS patients have common features including typical facial appearance, neutropenia, abnormal trunk fat distribution, microcephaly, myopia and retinal damage. My thesis project aimed to characterize the ophthalmologic phenotype of a mouse model Vps13bEx3/Ex3 to determine the molecular mechanisms involved in the development of CS retinopathy.First, we showed that Vps13bEx3/Ex3 mice develop a cataract between 2 and 3 months. Disorganization of the fibrous cells of the crystalline lens and their differentiation into mesenchymal cells were observed. At a more advanced stage, the external membrane of the crystalline lens is ruptured and the cortical and nuclear part of the crystalline lens separates. After the onset of cataract, the retina shows deformations characterized by thinning and deformation of its various layers which can lead to retinal folds 50 to 500µm long. There is also a strong proliferation of microglial cells as well as astrogliosis. The appearance of cataract in our model has led to an exhaustive review of the literature showing that cataract is present in 85% of patients at 40 years old and not related to retinopathy.We then showed a modification of the ocular phenotype in the presence of the Crb1Rd8 mutation. Crb1 is a transmembrane protein whose Rd8 variation leads to retinal disorganization. We have created cohorts of all possible Vps13b/Crb1 genotypes. Our preliminary analyses show early retinal dystrophy in mice Vps13bEx3/Ex3 Crb1Rd8/+, suggesting that Vps13b could be a Crb1 modifier gene. Molecular mechanisms that could lead to the appearance of SC retinopathy have been studied in Vps13bEx3/Ex3Crb1+/+ mice. The structure of the retina and these different cell populations were studied but did not reveal any abnormalities before the onset of the cataract. However, the study of inflammatory mechanisms showed an increase in sensitivity to IL6 in the retina of our model. This mechanism could be involved in the development of SC retinopathy. As the ocular phenotype is strongly decreased in mice Vps13bEx3/Ex3 Crb1+/+,the impact of environmental factors, especially light, has also been studied and shows that when subjected to high light intensity, mice develop retinopathies.In parallel, we have studied the ophthalmological characteristics of our Dijon cohort mainly using OCT. This study reveals (i) that macular edema is a frequent symptom of SC which remains relatively stable over time and (ii) that the onset of retinopathy is independent of that of cataract.Consequently, my PhD work has allowed to characterize the ophthalmic attacks of our Vps13bEx3/Ex3 mouse model and will allow to deepen the mechanistic knowledge of retinopathy and cataract of the CS, and could allow to develop a therapeutic target or prevention strategies for these ophthalmic lesions
14
Henricsson, Marianne. "Hyperglycaemia and diabetic eye complications a clinical and epidemiological study /". Lund : Lund University, 1997. http://catalog.hathitrust.org/api/volumes/oclc/39736643.html.
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15
Tam, Ka-wae Tammy. "Prevalence, risk factors and progression of diabetic retinopathy in Chinese elderly with type 2 diabetes mellitus : evidence for recommended screening interval /". View the Table of Contents & Abstract, 2006. http://sunzi.lib.hku.hk/hkuto/record/B36434346.
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Southern, Danielle A. "The measurement of progression of diabetic retinopathy". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/mq65135.pdf.
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Ariffin, Azrin Esmady. "Visual function in patients with diabetic retinopathy". Thesis, City University London, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.283151.
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18
Laughlin, William Edward. "Angiogenesis and vascular leakage in diabetic retinopathy". Thesis, University College London (University of London), 2018. http://discovery.ucl.ac.uk/10043874/.
Testo completoAbstract (sommario):
Diabetic retinopathy (DR) is the most common microvascular complication of diabetes and a leading cause of blindness. Increased vascular permeability in the retina following blood-retinal barrier (BRB) breakdown is a clinically significant event and a major cause of vision loss. VEGF blockade, despite being the only treatment to improve visual acuity, has a limited effectiveness for a majority of patients. A significant proportion of patients develop resistance to treatment, which implies that other factors are also involved in the pathology of this disease. There is currently a major unmet clinical need for therapeutics which target the early stages of DR prior to the onset of overt vascular symptoms. The aim of this thesis was to investigate early diabetes-induced changes to the retina and their effects on the vasculature, in order to identify novel potential therapeutic targets. This was achieved by investigating the effects of high glucose and glycated albumin on the vasculature using the mouse metatarsal assay, an ex vivo model of angiogenesis and the effects of diabetes on the retina with the streptozotocin-induced diabetic mouse. Both high glucose and glycated albumin altered angiogenesis in the metatarsal assay. Investigation of the diabetic mouse retina revealed evidence of increased inflammation and oxidative stress at the cellular and molecular level, accompanied with evidence of vascular leakage. qPCR analysis revealed an increase in Angptl6 and Lrg1 expression of which had not been investigated in the diabetic mouse retina before. Studies with transgenic mouse models implied that Lrg1 is involved in the early stages of pathophysiology of DR and may be a suitable therapeutic target prior to the onset of overt vascular symptoms.
19
Liu, Yiyuan. "Clinical and genetic determinants of diabetic retinopathy". Thesis, University of Dundee, 2014. https://discovery.dundee.ac.uk/en/studentTheses/5ac68285-0104-489d-9aad-c4b5dc15084f.
Testo completoAbstract (sommario):
Diabetic retinopathy is a microvascular complication of type 1 and type 2 diabetes, affecting the retinal vasculature of the eye. In the Scottish diabetic retinopathy grading scheme (version 1.1), the severity of diabetic retinopathy is classified as no retinopathy, mild background, observable background, severe non-proliferative and proliferative retinopathy. In the GoDARTS (Genetics of Diabetes Audit and Research Tayside) cohort, we have longitudinal data of retinopathy in diabetic patients since 1990. 3,734 and 3,673 GoDARTS patients were genotyped in the Affymetrix Genome-wide Human SNP Array 6.0 and Illumina HumanOmniExpress BeadChip, respectively. As the pathophysiology of diabetic retinopathy remains elusive, the aim of this thesis is to use the GoDARTS phenotype and genotype data to study clinical and genetic determinants for diabetic retinopathy.
20
Leontidis, Georgios. "Early screening and diagnosis of diabetic retinopathy". Thesis, University of Lincoln, 2016. http://eprints.lincoln.ac.uk/26473/.
Testo completoAbstract (sommario):
Diabetic retinopathy (DR) is a chronic, progressive and possibly vision-threatening eye disease. Early detection and diagnosis of DR, prior to the development of any lesions, is paramount for more efficiently dealing with it and managing its consequences. This thesis investigates and proposes a number of candidate geometric and haemodynamic biomarkers, derived from fundus images of the retinal vasculature, which can be reliably utilised for identifying the progression from diabetes to DR. Numerous studies exist in literature that investigate only some of these biomarkers in independent normal, diabetic and DR cohorts. However, none exist, to the best of my knowledge, that investigates more than 100 biomarkers altogether, both geometric and haemodynamic ones, for identifying the progression to DR, by also using a novel experimental design, where the same exact matched junctions and subjects are evaluated in a four year period that includes the last three years pre-DR (still diabetic eye) and the onset of DR (progressors’ group). Multiple additional conventional experimental designs, such as non-matched junctions, non-progressors’ group, and a combination of them are also adopted in order to present the superiority of this type of analysis for retinal features. Therefore, this thesis aims to present a complete framework and some novel knowledge, based on statistical analysis, feature selection processes and classification models, so as to provide robust, rigorous and meaningful statistical inferences, alongside efficient feature subsets that can identify the stages of the progression. In addition, a new and improved method for more accurately summarising the calibres of the retinal vessel trunks is also presented. The first original contribution of this thesis is that a series of haemodynamic features (blood flow rate, blood flow velocity, etc.), which are estimated from the retinal vascular geometry based on some boundary conditions, are applied to studying the progression from diabetes to DR. These features are found to undoubtedly contribute to the inferences and the understanding of the progression, yielding significant results, mainly for the venular network. The second major contribution is the proposed framework and the experimental design for more accurately and efficiently studying and quantifying the vascular alterations that occur during the progression to DR and that can be safely attributed only to this progression. The combination of the framework and the experimental design lead to more sound and concrete inferences, providing a set of features, such as the central retinal artery and vein equivalent, fractal dimension, blood flow rate, etc., that are indeed biomarkers of progression to DR. The third major contribution of this work is the new and improved method for more accurately summarising the calibre of an arterial or venular trunk, with a direct application to estimating the central retinal artery equivalent (CRAE), the central retinal vein equivalent (CRVE) and their quotient, the arteriovenous ratio (AVR). Finally, the improved method is shown to truly make a notable difference in the estimations, when compared to the established alternative method in literature, with an improvement between 0.24% and 0.49% in terms of the mean absolute percentage error and 0.013 in the area under the curve. I have demonstrated that some thoroughly planned experimental studies based on a comprehensive framework, which combines image processing algorithms, statistical and classification models, feature selection processes, and robust haemodynamic and geometric features, extracted from the retinal vasculature (as a whole and from specific areas of interest), provide altogether succinct evidence that the early detection of the progression from diabetes to DR can be indeed achieved. The performance that the eight different classification combinations achieved in terms of the area under the curve varied from 0.745 to 0.968.
21
Tonade, Deoye. "ROLE OF PHOTORECEPTOR CELLS IN DIABETIC RETINOPATHY". Case Western Reserve University School of Graduate Studies / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=case1505440070603758.
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Marahrens, Lydia, Focke Ziemssen, Andreas Fritsche, Tjalf Ziemssen, Raimar Kern, Peter Martus e Daniel Roeck. "Limited Time from the Diabetes Patients’ Perspective: Need for Conversation with the Eye Specialist". Karger, 2016. https://tud.qucosa.de/id/qucosa%3A70609.
Testo completoAbstract (sommario):
Purpose: Facing the lack of time, busy retina consultants should be aware of how the patients would prefer that time is spent and whether they wish the specialist to talk more at the expense of other medical activities. Methods: 810 persons with diabetes were asked to divide the time of 10 min between examination, consultation and treatment when envisioning a real-life scenario of diabetic retinopathy (NCT02311504). Results: With the increasing duration of diabetes, patients wanted significantly more time for diagnostics (p = 0.028), while age was found to be associated with less time for treatment (p = 0.009). Female subjects tended to prefer only little more time for talking (p = 0.051) in comparison with males, who slightly favored therapy (p = 0.025). Conclusions: The large majority recognized the need for diagnostics in their allocation of time. If individual patients are confronted with the health care perspective of time constraints, this might improve the understanding of prioritization.
23
Cheung, Shiu-fai. "Effects of endothelial cell-specific over-expression of endothelin-1 on diabetic and ischemic retinopathy". Click to view the E-thesis via HKUTO, 2006. http://sunzi.lib.hku.hk/hkuto/record/B36923060.
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Gustafsson, Sebastian. "Sight-threatening Diabetic Retinopathy in a Swedish County – : Prevalence and Comparison of Patients with and without Sight-threatening Diabetic Retinopathy". Thesis, Örebro universitet, Institutionen för medicinska vetenskaper, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:oru:diva-66795.
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Alexander, Henry George. "Factors associated with diabetic retinopathy requiring treatment on fundal photography in participants of the Cape Town diabetic retinopathy screening programme". University of the Western Cape, 2016. http://hdl.handle.net/11394/5498.
Testo completoAbstract (sommario):
Magister Public Health - MPHBACKGROUND AND RATIONALE: The Cape Town Metro District Health Service (MDHS) has introduced a Diabetic RetinopathyScreening (DRS) programme incorporating retinal fundal photography in diabetic services at primary health care (PHC) facilities. Hitherto, coverage of the DRS programme has been less than optimal in part due to volumes of diabetic patients attending PHC facilities. The aim of this study was to identify possible sub-groups of patients, attending the Cape Town DRS Programme, who are at most risk of diabetic retinopathy and might be prioritised for early diabetic retinopathy detection and subsequent sight-saving treatment. METHODOLOGY: A case-control study of risk factors for treatment-requiring diabetic retinopathy was conducted. This research sampled participants from the DRS programme provided by the MDHS eye care team to Type II diabetics attending public PHC facilities within the Klipfontein and Mitchells Plain Sub-Districts. Based on fundal images, cases were selected as those requiring ophthalmological treatment; and controls (three matched per case by area of residence) as those judged as not requiring ophthalmological treatment for diabetic retinopathy. Data on possible risk factors (clinical, laboratory) were extracted from the patients' folders. RESULT: The study included 453 participants, of whom 113 (24.9%) were cases and 340 (75.1%) were controls. Three factors were significantly associated with treatment-requiring diabetic retinopathy on multivariate analysis: Insulin dependency (OR of 2.96, 95% CI: 1.75 – 5.00); duration of diabetes of more than 10 years (OR of 3.44, 95% CI: 2.06 – 5.74) and sustained hyperglycaemia over the past six months (OR of 3.73, 95% CI: 1.69 – 8.22). A screening algorithm combining these criteria had a sensitivity of 61.2% (95% CI: 51.9 – 70.5). CONCLUSION: The findings indicate that a sub-set of patients attending the DRS programme in the Klipfontein and Mitchells Plain Sub-Districts have a greater likelihood of presenting with treatment-requiring diabetic retinopathy. Further research is required to develop a tool that is sufficiently sensitive to safely prioritise patients for fundal screening.
National Research Foundation (NRF)
26
Basu, Ansu. "Diabetic retinopathy screening using advanced digital imaging technology". Thesis, University of Newcastle upon Tyne, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.413265.
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Gibson, Donna Lee. "Retinopathy of prematurity in British Columbia, 1952-1983". Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/26261.
Testo completoAbstract (sommario):
In recent years, concern about a new epidemic of retinopathy of prematurity (ROP) has focused attention on the increasing incidence of the disease and the factors responsible for its most severe consequences. Two studies designed to address these issues were done using data from three sources: the B.C. Health Surveillance Registry (Registry), Physicians's Notices of Livebirth (PNOB), and the Vancouver General Hospital (VGH).
In the first study, Registry and PNOB records were used to determine crude annual birth weight-specific incidence rates for ROP in infants liveborn in the Province of British Columbia (B.C.) in the period 1952-1983. These rates showed that, in B.C., the original epidemic of the disease ended in 1954. Linear regression lines fitted for each of four birth weight categories showed that, in the 29 year period after 1954, there was a significant increase in the incidence of ROP-induced blindness in infants weighing less than 1000 grams at birth. To refine this observation, the data were sub-divided: the 29 year period, to two smaller periods, 1955-1964 and 1965-1983; the less than 1000 gram birth weight category to two sub-categories, 500-749 and 750-999 grams. Since the inter-period incidence should have been similar if the birth weight-specific incidence had not changed since the end of the original epidemic, the crude weight-specific rates for ROP-induced blindness in the early period were used to calculate the expected number of cases in the later period. When weight-standardized incidence ratios (SIR's) and 95% confidence limits were calculated, the results showed that, in the 750-999 gram sub-category, the SIR was significantly increased. Infants born in the period 1965-1983 were 3.07 times more likely to be ROP: blind than their equal weight counterparts in the earlier period. In infants weighing 500-749 and 1000 grams or more, there was no evidence to suggest an increase in incidence after 1954.
The second study was done to determine the cofactors that differentiate infants who are blinded by ROP from those who are not. Infants were included if (i) they were born in B.C. between 1955 and 1983, (ii) they were known to the Registry as being ROP: blind (cases) or not blind (controls), and (iii) they were born in or admitted to the VGH within 28 days of birth. When the data from all three data sources were dichotomized and analyzed using univariate techniques, two variables, respiratory distress syndrome (RDS) and neonatal weight loss, showed a significantly protective effect. The effect of RDS disappeared when the data were stratified by birth interval indicating that the observed association was confounded by time. When the variables were reanalyzed in continuous form, none were significantly associated with visual outcome. However, since the power of the cofactor study was extremely low, none of the variables that were included can be eliminated as potential cofactors for the induction of blindness in infants with ROP.Medicine, Faculty of
Population and Public Health (SPPH), School of
Graduate
28
Wendt, Gunvor von. "Screening for diabetic retinopathy : aspects of photographic methods /". Stockholm, 2005. http://diss.kib.ki.se/2005/91-7140-398-1/.
Testo completo
29
Sinthanayothin, Chanjira. "Image analysis for automatic diagnosis of diabetic retinopathy". Thesis, King's College London (University of London), 1999. https://kclpure.kcl.ac.uk/portal/en/theses/image-analysis-for-automatic-diagnosis-of-diabetic-retinopathy(163f8067-329d-4a48-b214-0ea70ba828d4).html.
Testo completo
30
Arun, Chankramath S. "Retinopathy screening : prevention of blindness due to diabetes". Thesis, University of Newcastle Upon Tyne, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.427289.
Testo completo
31
Goh, Kheng Guan. "Computer assisted photocoagulation for treatment of diabetic retinopathy". Thesis, Teesside University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.410911.
Testo completo
32
Usher, David Benjamin. "Image analysis for the screening of diabetic retinopathy". Thesis, King's College London (University of London), 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.404601.
Testo completo
33
Crosby-Nwaobi, Roxanne. "The relationship between diabetic retinopathy and cognitive impairment". Thesis, King's College London (University of London), 2012. https://kclpure.kcl.ac.uk/portal/en/theses/the-relationship-between-diabetic-retinopathy-and-cognitive-impairment(762590a4-0446-415e-baec-2a7361757125).html.
Testo completoAbstract (sommario):
One of the most significant complications of diabetes is retinopathy. Diabetic retinopathy (DR), a chronic progressive sight-threatening disease of the retinal microvasculature, is the leading cause of treatable blindness in the working age group. Another emerging complication of diabetes is cognitive impairment (Cl). The exact link between diabetes and Cl remains elusive. One theory is that microvascular changes in the brain may be responsible for change in cognition in diabetes. In this study, it was hypothesised that increased severity of DR was associated with impaired cognition (cerebro-microvascular disease) in individuals with Type 2 Diabetes (T2DM). 381 men and women with T2DM recruited to the South East London Diabetic Retinopathy Study were stratified by severity of DR (no/mild retinopathy and proliferative diabetic retinopathy (PDR)) and severity of diabetic maculopathy (non-clinically significant macular oedema (non-CSMO) and CSMO). Each subject underwent tests of cognitive function, psychosocial assessment, ophthalmic and physical examination. Bivariate analysis between categories of DR and maculopathy (ANOVA, Chi square) and ANCOVA for the cognitive scores by DR severity were conducted using SPSS v17. Severity of DR demonstrated an inverse relationship with Cl in patients with T2DM (fully adjusted model). No association was found between severity of maculopathy and Cl. Retinal arteriolar and venular dilation was associated with lower cognition scores in patients with no/mild retinopathy. Decreased levels of serum factor Apo A was associated with decreased cognition. Participants with Cl had consistently elevated risk of stroke compared to participants with no Cl, irrespective of their DR status. Cognition scores also varied by ethnic grouping; participants of ethnic minorities had significantly lower cognition scores than Caucasian participants.
34
Liu, Haitao. "NEUTROPHIL ELASTASE CONTRIBUTES TO THE EARLY DIABETIC RETINOPATHY". Case Western Reserve University School of Graduate Studies / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=case1552485945496003.
Testo completo
35
Sabtu, K. "Evaluation of diabetic retinopathy screening in Brunei Darussalam". Thesis, London School of Hygiene and Tropical Medicine (University of London), 2015. http://researchonline.lshtm.ac.uk/2391561/.
Testo completoAbstract (sommario):
In recognition of the increasing prevalence of diabetes in Brunei, and the expected increase in diabetic retinopathy (DR), primary health centre based DR screening was introduced in 2006 for seven health centres in the Brunei-Muara district. The Brunei National Prevention of Blindness from Diabetic Retinopathy is a policy document calling for DR screening to be made systematic at a national level. However, the effectiveness of the model in practice was not evaluated and the DR screening programme was launched without a baseline survey and situation assessment. Consequently, the responsiveness of the health system to embed a systematic approach to DR screening has faced many constraints and was slow to evolve. This study has provided evidence to support the implementation of the policy document and baseline information on the gaps and challenges within the key service provision stages for DR screening and treatment. The overall objective of this thesis was to evaluate the DR screening model in the Brunei-Muara District. Results from this study suggest that the DR screening model in Brunei-Muara is partially systematic. The main findings showed that key processes are in place at different stages of DR screening and treatment and that sufficient resources have been allocated to detect sight threatening diabetic retinopathy (STDR) at primary health centres (PHCs) and to treat STDR at the national eye centre (NEC). This was supported by the good DR annual screening uptake rates (77%) and low DR prevalence rates (5.8%) reported in this study. However, the lack of monitoring of both the implementation processes and screening effectiveness was viewed as key limitations in the programme. This was evident through process gaps observed throughout the DR screening and treatment pathway including the identification of patients for screening at PHCs, GP to DR referral process, referral for treatment processes to NEC and disease registers that were not integrated and lacked accuracy. This was also backed by evidence that DR screening coverage rates were low (56%) across all health centres. Based on a generic framework to analyse development of DR screening programmes used in this study, the existing screening model could be enhanced by improving screening coverage rates, universal access to DR treatment, trained and certified workforce, implementation of a call and recall system and systematic digital photography screening system. However, further studies are required before these recommendations could be implemented.
36
Dow, Courtney. "Dietary Factors, Type 2 Diabetes and Diabetic Retinopathy". Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS380/document.
Testo completoAbstract (sommario):
Contexte : Le diabète de type 2 (DT2) constitue une pathologie majeure, au lourd fardeau, associ ée à de nombreuses complications, comme la rétinopathie diabétique (RD). Des facteurs modifiables, comme l’alimentation, ont déjà été identifiés pour le DT2 et la RD mais certains aspects de leurs rôles restent à préciser. Objectifs : Les objectifs de cette thèse étaient d’examiner le rôle de l’alimentation, en particulier la consommation d’acides gras (AGs), et des autres facteurs modifiables liés au mode de vie sur le risque de DT2 et de synthétiser, interpréter et analyser la relation entre l’alimentation et la RD. Résultats : Les résultats suggèrent que le rôle des AGs sur le risque de DT2 et de la RD pourrait être différent selon leur type, et même varier au sein d’un groupe comme les AG polyinsaturés (AGPI). Les résultats suggèrent aussi qu’une forte adhésion aux recommandations alimentaires n’est pas associée avec le développement d’un DT2, mais en revanche une forte adhérence aux autres recommandations de santé (concernant le tour de taille, l’activité physique et le statut tabagique) est fortement associée avec un moindre risque de DT2. On a montré qu’avoir un mode de vie sain aurait pu empêcher la survenue de plus de la moitié des cas de DT2. Conclusions : Cette thèse a permis de préciser l’importance et la complexité du rôle de l’alimentation dans le développement du DT2 et de la RD. Elle montre aussi l’impact des comportements sains dans la pathologie de DT2 et confirme que le DT2 est en grande partie, une maladie évitable. Les efforts devraient se focaliser sur la modification des comportements de santé à la fois dans la population générale et atteinte de DT2 et notamment encourager une alimentation modérée et variéeBackground : Type 2 diabetes (T2D) presents a significant health burden that is associated with many complications, such as diabetic retinopathy (DR), that further burden people with diabetes. Modifiable risk factors, such as the diet, have been identified for both T2D and DR; yet certain aspects of the role of the diet remain unclear. Objectives : The main objectives of this thesis were therefore to examine the role and impact of the diet, and in particular, the consumption of fatty acids (FAs), and other modifiable behaviours on the risk of T2D and to summarize, interpret and analyze the relationship between the diet and DR using data from both the E3N and AusDiab cohort studies. Results : The results suggest that the role of FAs on the risk of T2D and DR may differ between and within subgroups, and by individual polyunsaturated fatty acids (PUFAs). The findings also suggest that strongly adhering to national dietary guidelines is not associated with the development of T2D, but strongly adhering to other recommendations for healthy behaviours (for waist circumference, physical activity and smoking) is strongly inversely associated with T2D. Modifiable behaviour could have prevented more than half of the cases of T2D. Conclusions : This work underlines the importance and the complexity of the role of the diet in the development of T2D and DR. It also illustrates the impact of healthy behaviour in the etiology of T2D and confirms that T2D is largely preventable. Efforts should focus on the modification of multiple healthy behaviours in populations, and promote diets that are moderate and widely varied
37
Lian, Jinxiao, e 連金晓. "An evaluation of systematic screening for diabetic retinopathy in Hong Kong". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2013. http://hdl.handle.net/10722/196489.
Testo completoAbstract (sommario):
Background: Screening for diabetic retinopathy (DR) has been proven effective and cost-effective in preventing blindness. Hong Kong (HK) has a mixed health care economy and, before this study, there was no systematic screening for DR. The optimal screening interval for DR screening is controversial with some countries extending it to 2 or more years. Risk algorithms tailor screening intervals to an individual but the safety of a 2-year interval and the validity of the Iceland Risk Algorithm (IRA) are uncertain in HK. This study assesses the impact of charging a co-payment for DR screening in the public sector, evaluates its cost-effectiveness and examines the use of an algorithm to determine optimal screening intervals for subjects in HK.
Methods: A randomized controlled trial (RCT) was conducted with subjects with diabetes from two general outpatient public clinics randomized to free screening or pay screening with a co-payment of HK$60. Cost-effectiveness analysis used a Markov cohort model to compare these with opportunistic screening. Incremental cost-effectiveness ratios (ICERs) were calculated and one way and probabilistic sensitivity performed. Subjects were followed up for two years to examine the safety of a 2-year screening interval and to test the validity of the IRA in predicting sight threatening diabetic retinopathy (STDR). A new prediction model using cohort data was developed using logistic regression and tested in a similar fashion.
Results: After randomization, 1316 in the free and 1277 in the pay group agreed to participate. Uptake of screening was 88.5% (1165/1316) and 82.4% (1052/1277) in free and pay groups respectively (Pearson chi=19.74, P<0.001). Being in the pay group was associated with lower uptake of screening (OR=0.59, 0.47 to 0.74) and lower detection rates of DR (OR=0.73, 0.60 to 0.90) after adjustment.
From the societal perspective, pay systematic DR screening rather than opportunistic screening gives an ICER of HK$94,630/QALY gained. Free rather than pay systematic screening, had an ICER of HK$199,741/QALY gained. Probabilistic sensitivity analysis showed when willingness to pay for a QALY was HK$186,186 or more, free systematic screening had the highest probability of being cost-effective.
The 2-year cumulative incidence of STDR was low for those with no DR (2.9%) and those who developed STDR did not experience severe visual loss during follow up. The IRA had good discrimination for identifying STDR, but significantly lacked calibration. The new prediction model improved discrimination and calibration compared with the IRA.
Conclusion: A number of people in the pay group did not uptake screening and appear to be higher risk cases. The inverse care law appears to operate even with this relatively small co-payment. From the societal perspective, free systematic screening was more cost-effective than pay within the WHO threshold of 1 x annual per capita GDP (HK$338,520) for a QALY. Free systematic screening can be considered the most cost-effective screening strategy from the societal perspective. We could tailor screening intervals according to individual risks using a new prediction model which appears safe and efficient but which requires further testing with follow-up data.published_or_final_version
Public Health
Doctoral
Doctor of Philosophy
38
McGee-Hall, Joanne M. (Joanne Moore). "Neuropsychological Functioning of Adult Subjects with Diabetic Retinopathy Compared to a Normal Blind Population". Thesis, University of North Texas, 1994. https://digital.library.unt.edu/ark:/67531/metadc277944/.
Testo completoAbstract (sommario):
To investigate the possibility that chronic diabetes mellitus was related to specific neuropsychological deficits, cognitive functioning was measured in subjects with diabetic retinopathy (without secondary disabilities), and in subjects classified as normal blind adults (also without secondary disabilities). The scores for the two groups were then compared.
39
De, la Torre Gallart Jordi. "Diabetic Retinopathy Classification and Interpretation using Deep Learning Techniques". Doctoral thesis, Universitat Rovira i Virgili, 2019. http://hdl.handle.net/10803/667077.
Testo completoAbstract (sommario):
La retinopatia diabètica és una malaltia crònica i una de les principals causes de ceguesa i discapacitat visual en els
pacients diabètics. L'examen ocular a través d'imatges de la retina és utilitzat pels metges per detectar les lesions
relacionades amb aquesta malaltia. En aquesta tesi, explorem diferents mètodes innovadors per a la classificació
automàtica del grau de malaltia utilitzant imatges del fons d'ull. Per a aquest propòsit, explorem mètodes basats en
l'extracció i classificació automàtica, basades en xarxes neuronals profundes. A més, dissenyem un nou mètode per a
la interpretació dels resultats. El model està concebut de manera modular per a que pugui ser utilitzat en d'altres
xarxes i dominis de classificació. Demostrem experimentalment que el nostre model d'interpretació és capaç de
detectar lesions de retina a la imatge únicament a partir de la informació de classificació. A més, proposem un mètode
per comprimir la representació interna de la informació de la xarxa. El mètode es basa en una anàlisi de components
independents sobre la informació del vector d'atributs intern de la xarxa generat pel model per a cada imatge. Usant el
nostre mètode d'interpretació esmentat anteriorment també és possible visualitzar aquests components en la imatge.
Finalment, presentem una aplicació experimental del nostre millor model per classificar imatges de retina d'una
població diferent, concretament de l'Hospital de Reus. Els mètodes proposats arriben al nivell de rendiment de
l'oftalmòleg i són capaços d'identificar amb gran detall les lesions presents en les imatges, que es dedueixen només
de la informació de classificació de la imatge.La retinopatía diabética es una enfermedad crónica y una de las principales causas de ceguera y discapacidad visual en los pacientes diabéticos. El examen ocular a través de imágenes de la retina es utilizado por los médicos para detectar las lesiones relacionadas con esta enfermedad. En esta tesis, exploramos diferentes métodos novedosos para la clasificación automática del grado de enfermedad utilizando imágenes del fondo de la retina. Para este propósito, exploramos métodos basados en la extracción y clasificación automática, basadas en redes neuronales profundas. Además, diseñamos un nuevo método para la interpretación de los resultados. El modelo está concebido de manera modular para que pueda ser utilizado utilizando otras redes y dominios de clasificación. Demostramos experimentalmente que nuestro modelo de interpretación es capaz de detectar lesiones de retina en la imagen únicamente a partir de la información de clasificación. Además, proponemos un método para comprimir la representación interna de la información de la red. El método se basa en un análisis de componentes independientes sobre la información del vector de atributos interno de la red generado por el modelo para cada imagen. Usando nuestro método de interpretación mencionado anteriormente también es posible visualizar dichos componentes en la imagen. Finalmente, presentamos una aplicación experimental de nuestro mejor modelo para clasificar imágenes de retina de una población diferente, concretamente del Hospital de Reus. Los métodos propuestos alcanzan el nivel de rendimiento del oftalmólogo y son capaces de identificar con gran detalle las lesiones presentes en las imágenes, que se deducen solo de la información de clasificación de la imagen.
Diabetic Retinopathy is a chronic disease and one of the main causes of blindness and visual impairment for diabetic patients. Eye screening through retinal images is used by physicians to detect the lesions related with this disease. In this thesis, we explore different novel methods for the automatic diabetic retinopathy disease grade classification using retina fundus images. For this purpose, we explore methods based in automatic feature extraction and classification, based on deep neural networks. Furthermore, as results reported by these models are difficult to interpret, we design a new method for results interpretation. The model is designed in a modular manner in order to generalize its possible application to other networks and classification domains. We experimentally demonstrate that our interpretation model is able to detect retina lesions in the image solely from the classification information. Additionally, we propose a method for compressing model feature-space information. The method is based on a independent component analysis over the disentangled feature space information generated by the model for each image and serves also for identifying the mathematically independent elements causing the disease. Using our previously mentioned interpretation method is also possible to visualize such components on the image. Finally, we present an experimental application of our best model for classifying retina images of a different population, concretely from the Hospital de Reus. The methods proposed, achieve ophthalmologist performance level and are able to identify with great detail lesions present on images, inferred only from image classification information.
40
Dembinska-Knypinski, Olga. "Structural and functionnal [sic] consequences of oxygen induced retinopathy". Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=36907.
Testo completoAbstract (sommario):
Retinopathy of prematurity (ROP) is a potentially blinding retinal disorder, which results from the exposure of the premature infant to hyperoxia. The diagnosis and the assessment of severity of ROP are based on the degree of retinal vascular abnormalities (such as avascular peripheral retina and neovascularisation), which are observed upon fundus examination. However, even if the vascular consequences of ROP are resolved, functional sequels such as high myopia, anisometropia and strabismus, may persist through adulthood. In severe cases, even more dramatic consequences, namely retinal detachment and blindness, may also occur. In oxygen-induced retinopathy (OIR), the animal model of ROP, hyperoxia-induced vasoobliteration and neovascularisation have been studied extensively in mice, rats, cats and dogs. However, the functional and ultrastructural changes that might result from the exposure to hyperoxia have not yet been examined in details. In this study, we report functional, as assessed with the electroretinogram (ERG), and structural, determined with histological sections of the retina, consequences of postnatal hyperoxia which took place during a period of intense retinal maturation, that is, the first 14 days of life of Sprague Dawley rats.Our results indicate that there is a sigmoidal dose-response correlation between the increasingly longer duration of oxygen exposure, and the decrease in the postreceptoral retinal activity, as revealed by the gradual reduction in the amplitudes of rod and cone dominated b-waves and oscillatory potentials. Furthermore, the cone function appeared to be slightly more affected than that of the rod. Also, of all the ERG components the oscillatory potentials, especially the short latency ones, appeared to be the most sensitive to the hyperoxia. The gradual thinning of the outer plexiform layer (OPL) is also correlated with the duration of oxygen exposure, while the reduction in the number of horizontal cells is not.
Secondly, our experimental approach has allowed us to evidence a period of higher oxygen susceptibility (a window), which takes place during the second week of life of the newborn rats, more specifically around postnatal day 10. Several oxygen exposures of short duration, which included this period, were shown to be more detrimental to the rod and cone function than longer exposures taking place prior to or after this window. This would suggest that during the normal maturation process, the immature retina is not equally sensitive to the hyperoxic insult, presumably because specific retinal structures (synapses in OPL) are targeted by oxygen.
Finally, Trolox C, a potent water-soluble antioxidant, partially prevents the functional and structural consequences of OIR. The prophylactic effect appears to benefit more the rod function than that of the cone.
To conclude, we believe that this new knowledge will help us understand the pathophysiological processes at the origin of oxygen toxicity in the immature retina, thus, significantly increasing our insights on the human form of this disease, namely ROP, which as a result, will be instrumental in devising new therapeutic avenues to help fight this potentially debilitating retinal disorder.
41
Olson, J. A. "Digital imaging, leucocytes, gamma-linolenic acid and diabetic retinopathy". Thesis, University of Aberdeen, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.593242.
Testo completoAbstract (sommario):
The work for this thesis has been carried out in the Diabetic Clinic, Woolmanhill, the Eye Clinic, Foresterhill and the Departments of Bio-Medical Physics and Ophthalmology, University of Aberdeen. One hundred and twenty two patients with type 1 diabetes mellitus were recruited from the Diabetic Clinic, Woolmanhill, and attended a Research Clinic at the Eye Clinic, Foresterhill, on a three monthly basis for two years each between 1992 and 1995. Data was extensively collated relating to diabetic control and diabetic complications. Concentrations and activities of several serum factors were studied in an attempt to elucidate pathogenetic mechanisms in diabetic retinopathy. Serum levels of soluble leucocyte endothelial adhesion molecules were measured to see if there is indirect evidence for increase leucocyte adhesion in diabetic retinopathy. Similar studies were also performed looking at serum induced retinal endothelial capillary cell migration, a putative early feature in the development of sight-threatening new vessel formation. Computer image analysis methods, developed in the Department of Bio-Medical Physics, were modified and evaluated, leading to robust techniques suitable for quantifying lesions of diabetic retinopathy in large numbers of unselected fundal photographs and fluorescein angiograms. This latter work was completed in 1997. As it is known that essential fatty acid metabolism in diabetes is abnormal, leading to low levels of gamma-linolenic acid and its metabolites, the above techniques were used to assess the progress of diabetic retinopathy in a two year crossover trial of dietary gamma-linolenic acid supplementation.
42
Goh, Jonathan. "The reading of diabetic retinopathy images - an evolutionary approach". Thesis, University of Surrey, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.543272.
Testo completoAbstract (sommario):
The problem of scalable image recognition has long been a research issue in the area of computer vision. This thesis aims to address this by providing a holistic solution in which ensembles of very large number of classifiers for various image content are initially developed in order to cover as many perspectives of problem space as possible. The selection of these classifiers is then optimised simultaneously using evolutionary algorithms to ensure that the features and classifiers selected are optimal for the heterogeneous system components. To model image context, Hidden Markov Models are established through various evolutionary computation processes. Especially a hybrid evolutionary approach has been developed to find the most suitable contextual models which concurrently guide the searching for optimal classifiers. Finally information from optimised classifiers and context models are fused together to reason and determine the overall image content. This proposed architecture has been tested on Diabetic Retinopathy (DR) image datasets, which exhibit great variability and diversity. Based on the proposed solution, the system is able to recognise the key DR signs and ultimately, to separate normal and abnormal diabetic retinopathy images. Through evolutionary computation, the various components of the system outperformed classical approaches. This is demonstrated through the comparison between combined optimal classifiers and those obtained through traditional combination strategies such as average, sum and majority vote. Experiments also show that hybrid evolutionary approaches for optimising the classifier combination strategy and context models simultaneously perform best, if each component is treated individually. Using the integrated approach, the system developed is capable of separating normal and abnormal retina image with a Sensitivity of 95% and a Specificity of 92%. Among all images the system recognises as normal, 91% are true normal ones
43
Godfrey, Lynne. "Screening for diabetic retinopathy : a hospital based screening service". Thesis, City University London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.287666.
Testo completo
44
Stottrup, Casey. "Cell-cell communication in the pathogenesis of diabetic retinopathy". Thesis, Boston University, 2012. https://hdl.handle.net/2144/12642.
Testo completoAbstract (sommario):
Thesis (M.A.)--Boston University
PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you.Purpose: The goal of this study is to test the hypothesis that high glucose, a prevalent characteristic of diabetes, induces vascular cell death associated with diabetic retinopathy by compromising gap junction intercellular communication. Methods: Cell culture models of hyperglycemia involving endothelial cells, pericytes, and Muller cells were used in this study. Cells were exposed to high glucose (HG: 30 mM) for 7 days and harvested for analysis of Cx43, ZO-1, rab20, and β-actin by Western blot and subsequent densitometric analyses using imageJ software. Immunoprecipitation was performed to identify rab20 by Western blot analysis. Localization and distribution of the tight junction and gap junction proteins were determined by immunostaining. Cells immunostained for Cx43 and ZO-1 were digitally photographed under immunofluorescence microscopy and assessed for protein localization and distribution. To determine the effect of reduced rab20, cells were transfected with rab20 siRNA in the presence of Lipofectin; scrambled siRNA was used as control. To identify cells undergoing apoptosis, TUNEL assay was performed. Results: Western blot analysis revealed that HG significantly reduced Cx43 protein expression in rMC-1 (64% of N) and cocultures of rMC-1 and BRPs (72% of N). Similarly, Cx43 and ZO-1 immunostaining were significantly reduced in these cells grown in HG condition. Western blot analysis also revealed that HG significantly upregulated rab20 (129% of N) protein expression. Under HG condition, an increased number of TUNEL+ cells was detected using TUNEL assay (7.3 vs. 1.5 TUNEL+ cells per 1000 cells). HG cells transfected with rab20 siRNA significantly reduced the number of apoptotic cells (1.5 vs. 7.3 TUNEL+ cells per 1000 cells). Conclusion: Findings from this study indicate that HG-induced disturbed gap junction intercellular communication may contribute to retinal vascular cell and Muller cell apoptosis. HG-induced overexpression of rab20 may play a significant role in reducing Cx43 expression and compromising cell-cell communication associated with the pathogenesis of diabetic retinopathy.
45
Welikala, Roshan Alex. "Automated detection of proliferative diabetic retinopathy from retinal images". Thesis, Kingston University, 2014. http://eprints.kingston.ac.uk/30591/.
Testo completoAbstract (sommario):
Diabetic retinopathy (DR) is a retinal vascular disease associated with diabetes and it is one of the most common causes of blindness worldwide. Diabetic patients regularly attend retinal screening in which digital retinal images are captured. These images undergo thorough analysis by trained individuals, which can be a very time consuming and costly task due to the large diabetic population. Therefore, this is a field that would greatly benefit from the introduction of automated detection systems. This project aims to automatically detect proliferative diabetic retinopathy (PDR), which is the most advanced stage of the disease and poses a high risk of severe visual impairment. The hallmark of PDR is neovascularisation, the growth of abnormal new vessels. Their tortuous, convoluted and obscure appearance can make them difficult to detect. In this thesis, we present a methodology based on the novel approach of creating two different segmented vessel maps. Segmentation methods include a standard line operator approach and a novel modified line operator approach. The former targets the accurate segmentation of new vessels and the latter targets the reduction of false responses to non-vessel edges. Both generated binary vessel maps hold vital information which is processed separately using a dual classification framework. Features are measured from each binary vessel map to produce two separate feature sets. Independent classification is performed for each feature set using a support vector machine (SVM) classifier. The system then combines these individual classification outcomes to produce a final decision. The proposed methodology, using a dataset of 60 images, achieves a sensitivity of 100.00% and a specificity of 92.50% on a per image basis and a sensitivity of 87.93% and a specificity of 94.40% on a per patch basis. The thesis also presents an investigation into the search for the most suitable features for the classification of PDR. This entails the expansion of the feature vector, followed by feature selection using a genetic algorithm based approach. This provides an improvement in results, which now stand at a sensitivity and specificity 3 of 100.00% and 97.50% respectively on a per image basis and 91.38% and 96.00% respectively on a per patch basis. A final extension to the project sees the framework of dual classification further explored, by comparing the results of dual SVM classification with dual ensemble classification. The results of the dual ensemble approach are deemed inferior, achieving a sensitivity and specificity of 100.00% and 95.00% respectively on a per image basis and 81.03% and 95.20% respectively on a per patch basis.
46
MacCormick, I. "Malarial retinopathy and neurovascular injury in paediatric cerebral malaria". Thesis, University of Liverpool, 2016. http://livrepository.liverpool.ac.uk/2049100/.
Testo completoAbstract (sommario):
Background Diseases of the brain are difficult to study because this organ is relatively inaccessible. Only one part of the central nervous system is available to direct, non-invasive observation – the retina. The concept of the retina as a window to the brain has created much interest in the retina as a source of potential markers of brain disease. Paediatric cerebral malaria is a severe neurological complication of infection with the parasite Plasmodium falciparum, which is responsible for death and disability in a significant number of children in sub-Saharan Africa. As with many neurological diseases, the precise mechanisms by which this infection causes damage to the brain remain unclear, and this hampers efforts to develop effective treatments. It may be that studying the retina in paediatric cerebral malaria could both illuminate pathogenesis specific to this disease, and also provide an illustration of how to approach retinal biomarkers in a new, and potentially more effective way. Methods I approached the aim of developing retinal features as markers of brain disease in paediatric cerebral malaria via several objectives. I made use of an existing clinical study to collect new retinal data from ophthalmoscopic examinations and fundus fluorescein angiograms from patients over three successive malaria seasons in Malawi, and added these to historical data obtained previously at the same site. I devised a new method for grading retinal images. I reviewed the biological plausibility of associations between retina and brain in cerebral malaria, and then considered analytical methods to interpret my retinal data effectively. Finally I estimated associations between retinal features, outcomes, and a radiological measure of brain swelling using combinations of regression models. Results My review of retinal and cerebral histopathology, vascular anatomy and physiology indicated that certain retinal and brain regions may be similarly prone to damage from sequestration as a result of interactions between aberrant rheology and microvascular geometry, such as branching patterns and arteriole to venule ratios. My review of evaluations of analogy and surrogacy suggested that biological similarities between retina and brain could be used to justify statistical evaluation of the amount of information the subject and object of the inference share about a common outcome, as used to assess surrogate end points for clinical trials. This kind of approach is able to address questions about whether a particular retinal feature is effectively equivalent to an analogous disease manifestation in the brain. I report analyses on three overlapping groups of subjects, all of whom had retinopathy positive cerebral malaria: children with admission ophthalmoscopy (n=817), children with admission fluorescein angiography (n=260), and children with admission angiography and MRI of the brain (n=134). Several retinal features are associated with death and longer time to recover consciousness in paediatric cerebral malaria. Broadly speaking, these features appear to reflect two processes: neurovascular sequestration (e.g. orange vessel discolouration and death), and neurovascular leakage (e.g. >5 sites of punctate leak and death). Respective adjusted odds ratios and 95% confidence intervals for these particular associations are: 2.88 (1.64-5.05); and 6.90 (1.52-31.3). Other related processes may also be important, such as ischaemia, which can be extensive. Associations between retina and brain are less clear, in part because of selection bias in the samples. Conclusions Neurovascular leak is important in fatal paediatric cerebral malaria, suggesting that fatal brain swelling may occur primarily as a result of vasogenic oedema. Other processes are also likely to be involved, particularly neurovascular sequestration, which is visible on retinal imaging as orange vessels or intravascular filling defects. Sequestration may plausibly cause leak through direct damage to tight junctions and by increasing transmural pressure secondary to venous congestion. Several types of retinal leakage are seen and some of these may represent re-perfusion rather than acute injury. Future work to investigate temporal changes in retinal signs may find clearer associations with radiological and clinical outcomes. The steps taken to evaluate retinal markers in cerebral malaria illustrate a more rigorous approach to retinal biomarkers in general, which can be applied to other neurological diseases.
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Abedi, Natasha. "Retinopathy of prematurity (ROP) in Örebro : a 10-yearperspective". Thesis, Örebro universitet, Institutionen för medicinska vetenskaper, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:oru:diva-86364.
Testo completoAbstract (sommario):
Background: The survival rate of premature infants has increased in Sweden over the pastdecade. Preterm infants run the risk of developing a potentially blinding disease known asretinopathy of prematurity (ROP). A recent Swedish national study showed that the frequencyof ROP has increased over the past years and there are regional differences across the country. Aim: Our aim was to evaluate the frequency of ROP in Örebro region (Örebro) and comparewith the rest of Sweden over a 10-year period. Methods: A retrospective cohort study was conducted on all premature infants born beforegestational week 31, screened for ROP in Örebro, from 2008 to 2017. Data such as number ofinfants, birth weight (BW), gestational age (GA) and ROP-outcome was retrieved from anational quality register; SWEDROP. Comparisons were made with national data during thesame time-period. Results:The study included 200 infants with a median GA of 28.4 weeks and BW 1144 grams.Of the screened infants 99 (49.5%) developed ROP and 20 (10%) were treated during the studyperiod. During the study period, mild ROP decreased (p=0.024), severe ROP increased(p=0.032), however there was no change in ROP-treated infants (p=0.159). The percentage ofROP-treated infants was higher in Örebro than the rest of Sweden (p=0.024). Conclusion: Our study showed that the frequency of mild ROP decreased in Örebro whilstsevere ROP increased during the 10-year period. The frequency of infants treated for ROP wassignificantly higher in Örebro compared to the rest of Sweden.
48
Hamilton, Ross Waring. "The role of erythropoietin in protecting against diabetic retinopathy". Thesis, Queen's University Belfast, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.546354.
Testo completo
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Lungershausen, Meike. "Internet-basiertes Screening-System für diabetische Retinopathie". [S.l.] : [s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=970259875.
Testo completo
50
Misse, Patrick. "Rétinopathie du diabétique sous pompe à insuline après 5 ans d'évolution". Montpellier 1, 1988. http://www.theses.fr/1988MON11036.
Testo completo