An investigation of the spectral reflectance of the fundus in normals and patients with common eye diseases was carried out using a multi wavelength scanning laser ophthalmoscope (SLO). With a knowledge of the spectral properties of the principal ocular pigments in the fundus, the appearance of the retina and choroid is predictable in normal subjects. The optic disc has a characteristic dark appearance when viewed with the SLO, and reasons for this may include a filtering effect of the confocal aperture to reduce the return of scattered light to the detector. In patients with macular exudates these features have a high reflectance in green-yellow light. An image processing method has been developed to quantify exudates and this was applied to SLO images and digitised colour slides of the same patients. Results show similar performance of processing in both image types with high accuracy (90% sensitivity for 95% specificity). A similar experiment was carried out on patients with macular drusen. These structures are of lower intensity than exudates and may have less well-defined borders. Again performance of the image processing methods showed broadly similar performance when comparing SLO images and digitised colour slides (60 to 68% sensitivity for 95% specificity). A study was carried out to assess the ability of the SLO to image the fundus in patients with cataract using a range of wavelengths. In conclusion the SLO offers the ability to image the fundus at selected wavelengths to enhance the desired features under investigation. As a fundus camera, used to generate digital images, it is unlikely to offer significant improvements over commercially available digital imaging CCD cameras. However, the SLO has properties which are likely to make it an ideal instrument for reflectometry, angiography and fundus topography. These applications are discussed in the final chapter.

No description available.

Lower back injuries are an illness which plague our society. Although almost everyone will experience some form of lower back pain in his or her lifetime, it is a sickness that is poorly understood, calling for new and innovative research. Much of this back pain is attributed to mechanical factors. Hence, it is important to understand the mechanics of the spine and the mechanical effects of degenerative changes that may lead to back pain. The spine is a complex three-dimensional structure and it is therefore necessary to study its mechanics with in vitro tests that replicate physiological movements as closely as possible. Traditional spinal testing machines have been unable to simulate the kinematic behaviour of intervertebral joints as they have limited degrees of freedom and cannot produce dynamic motion. The first aim of this research was to commission a robotic testing facility to overcome the limitations of traditional testing machines. This facility incorporated a six degree-of-freedom (DOF) robot arm with a six DOF force transducer. Mechanical tests performed on this facility could simulate the dynamic three-dimensional kinematics of the lumbar spine. In addition, this research aimed to assess the existence of a region of laxity during spinal joint motion defined as the Neutral Zone, and to determine the effect of specific lesions introduced into the intervertebral disc. To investigate these aims, in vitro mechanical tests on spinal specimens were performed using the robotic testing facility. To ensure these tests produced experimental results that were indicative of the mechanics of the spine in life, the intervertebral disc height had to be representative of the disc height in life. A set of experiments was performed to determine a method for ensuring this. The post-mortem disc height change due to a period of time exposed to a moist environment, freezing, defrosting and application of a constant compressive load was documented in a group of sheep spines. Specimens that were frozen immediately upon removal from the body produced the most predictable results. These specimens required no preloading to ensure the disc height during mechanical testing was similar to that in life. In accordance with this result, specimens used in the ensuing mechanical tests were frozen immediately on removal from the body and stored frozen until required for testing. Tests performed on sheep spines with the robotic facility verified the existence of a Neutral Zone. A criterion was determined that defined the Neutral Zone as the region of spinal joint rotation where the gradient of the load/deformation curve is within +/-0.5 dNm/degree from zero. This definition was used to determine the extent of the Neutral Zone in spinal motion during different movements. A Neutral Zone of approximately four degrees was found in intact spinal motion segments during flexion/extension. Only spinal musculature can stabilise the spine in this region of rotation. The removal of the zygapophysial joints increased the Neutral Zone in flexion/extension by approximately two degrees and caused the appearance of a Neutral Zone in axial rotation of approximately one degree. This suggests that during these motions, the zygapophysial joints are the main passive stabilisers. The mechanical effects of intervertebral disc lesions were examined by experimentally introducing three types of tears (rim lesions, radial tears and concentric tears) into sheep intervertebral discs and comparing the mechanical response of the injured joint to the joint's response prior to the creation of the lesions. Radial tears and concentric tears had no effect on the maximum moments resisted by the intervertebral disc or the hysteresis of the joint's response to motion. An anterior rim lesion increased the Neutral Zone by approximately 1.5 degrees and reduced the maximum moment resisted by the intervertebral disc by approximately 20% during extension in L1/L2 specimens. Rim lesions were also found to reduce the maximum moment resisted by the intervertebral disc in lateral bending and axial rotation for all levels by approximately 15% and 25% respectively. Rim lesions did not affect the hysteresis of intervertebral disc motion. In summary, this research commissioned a robotic testing facility capable of simulating the dynamic, three-dimensional kinematics of the lumbar spine and provided a unique insight into the three-dimensional mechanics of intervertebral joints. Testing was performed on sheep joints, however the outcomes provide an insight into the mechanical response of the human spine. The Neutral Zone was shown to exist but only in flexion/extension. This implies that damage to the spinal muscles may produce an unstable structure during flexion/extension within this Neutral Zone. Rim lesions reduce the ability of the intervertebral disc to resist all modes of motion. This suggests that the presence of rim lesions will produce overloading of other spinal elements and instigate progressive degenerative changes.

Thesis (Ph.D.)--University of Wisconsin--Madison, 2006. / Includes bibliographical references. Also available on the Internet.

Zugl.: Berlin, Charité, Univ.-Med., Habil.-Schr., 2006

Thesis (Ph.D.)--University of Western Australia, 2004.

Thesis (Ph. D.)--University of Missouri--Columbia, 1998. / "May 1998." Typescript. Vita. Includes bibliographical references (leaves 176-210). Also available on the Internet.

Thesis (M.S.)--University of Michigan, 1989.

Thesis (Ph.D.)--University of Wisconsin--Madison, 2006. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--Virginia Commonwealth University, 2009. / Prepared for: Dept. of Physiology. Bibliography: leaves 171-206. Also available online via the Internet.