Diss. (sammanfattning) Stockholm : Karol. inst. / Härtill 6 uppsatser.

Thesis (Ph. D.)--University of Oklahoma. / Bibliography: leaves 132-156.

Diabetic Retinopathy (DR) is a disorder of the retinal vasculature. It develops to some degree in nearly all patients with long-standing diabetes mellitus and can result in blindness. Screening of DR is essential for both early detection and early treatment. This thesis aims to investigate automatic methods for diabetic retinopathy detection and subsequently develop an effective system for the detection and screening of diabetic retinopathy. The presented diabetic retinopathy research involves three development stages. Firstly, the thesis presents the development of a preliminary classification and screening system for diabetic retinopathy using eye fundus images. The research will then focus on the detection of the earliest signs of diabetic retinopathy, which are the microaneurysms. The detection of microaneurysms at an early stage is vital and is the first step in preventing diabetic retinopathy. Finally, the thesis will present decision support systems for the detection of diabetic retinopathy and maculopathy in eye fundus images. The detection of maculopathy, which are yellow lesions near the macula, is essential as it will eventually cause the loss of vision if the affected macula is not treated in time. An accurate retinal screening, therefore, is required to assist the retinal screeners to classify the retinal images effectively. Highly efficient and accurate image processing techniques must thus be used in order to produce an effective screening of diabetic retinopathy. In addition to the proposed diabetic retinopathy detection systems, this thesis will present a new dataset, and will highlight the dataset collection, the expert diagnosis process and the advantages of the new dataset, compared to other public eye fundus images datasets available. The new dataset will be useful to researchers and practitioners working in the retinal imaging area and would widely encourage comparative studies in the field of diabetic retinopathy research. It is envisaged that the proposed decision support system for clinical screening would greatly contribute to and assist the management and the detection of diabetic retinopathy. It is also hoped that the developed automatic detection techniques will assist clinicians to diagnose diabetic retinopathy at an early stage.

Background: The International Diabetes Federation estimates that the number of adults with diabetes in Africa will increase by 98% by the year 2030. The importance of diabetic retinopathy as a cause of blindness has increased because of longevity and a decline in the other preventable causes of blindness in developing countries. Retinopathy diagnosed early, followed closely, and treated timeously with retinal laser therapy, prevents blinding retinopathy. The objective of the study is to determine the prevalence of Diabetic Retinopathy, its determinants and the acceptability as well as accessibility of the screening service by patients. Methods: The study is a cross-sectional study conducted at Gaborone diabetic retinopathy screening clinic. Convenience sampling was used where every eligible patient that arrived for DR screening and had consented was included in the study. Basic descriptive statistics of the study sample were reported and a multivariate analysis was performed with DR as the outcome of interest. Results: A total of 220 participants attended the clinic between 12th of January and 6th of February 2015. The mean age of the participants was 55.96 (p=0.32) years and females comprised the majority 65.45% (n= 144, p=0.33)) of participants. A fifth of the participants (n=43, p=0.67) felt they had poor knowledge of diabetes and 25.91% (n=57, p=0.96) stated they did not understand the purpose of screening. Only 63.64% (n=140, p=0.46) reported to always being compliant with their medication and compliance did not differ significantly between those who had retinopathy and those who did not. Traditional medicine use was reported in 16.36% of the participants (n=36, p=0.33). Diabetic Retinopathy was found in 31.82% (n=70) of the population and of those, 3 participants (1.36%) had referable DR. Maculopathy was found in 21.82% (n=48) of participants. Increasing household number and years living with DM were the only variables found to have a significant association with development of diabetic retinopathy. Conclusion: The prevalence of diabetic retinopathy has increased in our population compared to previous studies. The number of Diabetics attending the DR screening service in Gaborone has also increased but continuous diabetes health education cannot be over emphasized. Incorporation of local cultural values into the overall management of the disease is the best way to increase patient compliance.

Diabetes is a disease characterized by high blood glucose levels that result from a defect in the body’s inability to produce or utilize insulin. This disease increases the risk of long-term health problems and affects multiple organ systems; one complication being diabetic retinopathy (DR) that causes changes in the blood vessels of the retina. Diabetic retinopathy is the leading cause of blindness in the working age population. Early events in the pathogenesis of diabetic retinopathy are characterized by retinal vascular cell loss and excess retinal capillary leakage. Studies have shown that the retinal vascular cell loss occurs by programmed cell death while excess permeability develops at least in part through compromised tight junctions. Studies, including those from our laboratory, have also established that high glucose or diabetes reduces a specific protein, Cx43, found in intercellular communication channels or gap junctions, and contributes to the development of programmed cell death. It is currently unknown if there is an association between high glucose- or diabetes-induced Cx43 downregulation and excess permeability. Importantly, previous studies have shown that reduced Cx43 can promote excess permeability, but the mechanism underlying this phenomenon is not well understood. In this study, the effects of reduced Cx43 expression on proteins involved in cell-cell adhesion, or tight junctions, was examined. Specifically, experimentally induced Cx43 downregulation by a gene silencing technique affected the expression of tight junction proteins (ZO-1, occludin, claudin-5) in rat retinal endothelial cells. ZO-1 and occludin protein levels were decreased while claudin-5 levels were increased. In addition, permeability was increased when Cx43 was downregulated. These observations suggest that expression levels of Cx43 regulate barrier characteristics by influencing the expression of tight junction proteins. Findings from this study provide an insight into how high glucose-induced Cx43 downregulation compromises endothelial barrier characteristics through modulation of tight junction proteins. / 2031-01-01

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.

No description available.

Diss. (sammanfattning) Stockholm : Karol. inst., 2005. / Härtill 4 uppsatser.

Thesis (Ph. D.)--Ohio State University, 2008. / Title from first page of PDF file. Includes bibliographical references (p. 117-129).

The early detection of acquired losses of colour vision can provide the ophthalmologist with a very sensitive indicator of visual dysfunction. As a result we have developed and tested an automated, CRT-based, chromatic discrimination system that allows us to measure acquired colour-vision deficits with great precision. This system, known as the Sussex Gratings Machine, can produce chromatic stimuli in any direction in equal luminance colour space. However, we have found that measurements made along a constant MIL-cone axis (Tritan) or a constant S-cone (Red/Green) confusion axis are most useful. Using this system we have investigated acquired colour vision deficits in diabetes ,. and thyroid eye disease. We have shown that tritan discrimination losses can be used to screen for severe diabetic retinopathy and also to predict those who are likely to develop it within 18 months. We have also confirmed that acquired tritan discrimination losses are a very useful indicator of optic-nerve compression in thyroid eye disease.