Author: Rahul Yadav

Publisher:

Published: 2012

Total Pages: 181

ISBN-13:

"Despite advances in optical coherence tomography (OCT) there is still demand for further improvements in axial and lateral resolution, imaging depth and speed. The objectives of this dissertation were to develop advanced OCT systems that overcome some of the current limitations of this technique and to advance our understanding of the mechanism of human accommodation and corneal diseases by imaging the anterior segment of the eye. A large scan depth OCT (imaging depth > 10 mm) was developed for improving our understanding of accommodation. Novel scanning optics, where scanning beams are incident normal to the four ocular surfaces (anterior and posterior cornea and lens surface) was used in the system, to maximize the OCT signal. In-vivo imaging was carried out in two young normal subjects and the four anterior segment ocular surfaces could be visualized. Six millimeter diameter posterior lens surface could be imaged without the need for pupil dilation. Reduction in anterior chamber depth, increase in lens thickness and decrease in radius of curvature in both lenticular surfaces was observed with accommodation. An ultrahigh axial resolution OCT was developed to quantify structural changes in corneal diseases. The system, based on spectral domain OCT principle, used a broadband supercontinuum light source (375 nm at center wavelength of 812.5 nm) and was assembled in free space to avoid image degradation due to dispersion. A spectrometer based on modified Czerny Turner configuration was used to achieve relatively large scan depth (~1 mm). The experimentally measured axial resolution of the system was 1.1 [mu]m in corneal tissue, which allowed for the visualization and quantification of individual corneal layers in normal and diseased corneas. The clinical viability of the system was proven through a study on structural changes in the epithelium and Bowman's layer of keratoconic eyes. In-vivo cellular imaging capability, using an optical coherence microscope, was demonstrated by imaging stromal keratocytes and endothelial cells in the mouse cornea. The system provided large working distance (30.5 mm) and also has the potential of achieving larger field if imaging speed could be improved. Thus creating the possibility of performing non-invasive follow up investigation on the cellular structure in the mouse eyes. These advanced OCT systems have successfully overcome the limitations of currently available OCT systems, by providing better axial and lateral resolution and imaging depth. With improved performance these systems can help us in understanding the diseases pertaining to the anterior segment of the eye"--Pages ix-x.