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Thesis (Ph. D.)--University of Canterbury, 2007. / Typescript (photocopy). "1 August 2007." Includes bibliographical references (p. [245]-256). Also available via the World Wide Web.

Thesis (M.D.S.) -- Dept. of Dental Health, University of Adelaide, 1981. / Typescript (photocopy).

Thesis (M.S.)--Rochester Institute of Technology, 1992. / Typescript. Includes bibliographical references (leaves 104-108).

Thesis (Ph. D.)--University of Texas at Austin, 2003. / Vita. Includes bibliographical references. Available also from UMI Company.

This thesis is concerned with the measurement of blood flow and oxygen saturation in the microcirculation using the techniques of laser Doppler flowmetry and pulse oximetry. An investigation of the responses of Doppler flowmeters using different signal processing bandwidths and laser sources revealed two major findings. Firstly, that careful choice of processing bandwidth is required in order to sample the whole range of possible Doppler frequencies present in the backscattered light. Secondly, that the choice of laser source is important in governing the output stability of a flowmeter. Another investigation focused on the evaluation of a dual channel laser Doppler flowmeter using both in vitro and in vivo models. It was demonstrated that the instrument permitted a useful method of obtaining flow information by comparing simultaneous responses at experimental and control sites. The choice of laser wavelength was investigated in a study to determine whether blood flow measurements are obtained from different depths within the skin tissue. The results indicate that some depth discrimination is obtainable using instruments operating at different wavelengths, however it is difficult to demonstrate the effect in vivo. In a separate study it was shown that pressure applied to the skin surface greatly affects the underlying blood flow. It is recommended that care has to be taken when positioning Doppler probes on the skin. A reflection pulse oximeter was developed using laser light backscattered from the skin. The instrument was evaluated in vitro and in vivo by comparing desaturation responses with a commercial transmission pulse oximeter. The reflection oximeter was demonstrated to reliably follow trends in oxygen saturation but several problems prevented instrument calibration. Finally, a device combining laser Doppler flowmetry with reflection pulse oximetry was developed and used in vivo to follow trends in blood flow and oxygen saturation from the same tissue sample.

BACKGROUND: Using laser speckle flowgraphy to calculate retinal blood flow, we sought to measure changes in optic nerve blood flow compared to the normal fellow eye (relative blood flow) and changes in vision in patients with central retinal artery occlusions of varying duration. METHODS: Laser speckle flowgraphy was used to measure optic nerve blood flow in eyes with central retinal artery occlusions and the normal fellow eye of patients seen at Beth Israel Deaconess Medical Center to calculate relative blood flow. Visual acuity was assessed monocularly using Snellen Charts in a standardized fashion. RESULTS: In healthy control patients (n=20), relative blood flow was calculated to be 1.02 (p= 0.6843), indicating no significant difference in blood flow between eyes. In patients with unilateral central retinal artery occlusions (n=7), relative blood flow was calculated to be 0.66 ± 0.13 (p < .001), indicating on average a 33 percent loss in blood flow through the optic nerve head. When comparing relative blood flow values of CRAO patients measured within one year of vision loss versus patients when measured after one year of reported vision loss, values of patients measured within one year were lower. CONCLUSIONS AND RELEVANCE: Laser Speckle Flowgraphy has been shown to be a useful diagnostic tool that can reliably provide quantitative information on retinal blood flow. Results suggest that blood flow through the optic nerve head does return over time, presumably as the occlusion resolves or recanalizes. Longitudinal analysis determined a higher relative blood flow in patients one-year post incident versus within one year. However no statistically significant difference in visual acuity between these groups was found, indicating that return of blood flow is not associated with a return in visual acuity. Relative blood flow may be a useful measure of retinal perfusion in other retinal vascular disorders.

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