All ETDs from UAB

Advisory Committee Chair

Xincheng Yao

Advisory Committee Members

Franklin R Amthor

Christine A Curcio

Allan C Dobbins

Lei Liu

Andrew E Pollard

Document Type

Dissertation

Date of Award

2014

Degree Name by School

Doctor of Philosophy (PhD) School of Engineering

Abstract

The retina suffers pathological changes after attacked by eye diseases. The objective of my PhD dissertation is to explore intrinsic biomarkers for noninvasive assessment of retinal morphological structure and physiological function. Fundus autofluorescence (FAF), optical coherence tomography (OCT), etc. have provided indispensable information for eye disease detection. However, better understanding of the intrinsic biomarkers in FAF and OCT is desirable for quantitative interpretation of clinical outcomes. The first specific aim of the dissertation research was to characterize FAF signals across the whole retinal depth using two-photon excitation. FAF signals are usually attributable to fluorophores from the choroidal vessel and the retinal pigment epithelium. However, whether other retinal layers contribute to FAF is still unknown. Results from my study showed that FAF signals existed throughout all retinal layers. The second specific aim was to investigate the anatomic correlates to the presumed `inner segment/outer segment' (`IS/OS') OCT band. This was accomplished by comparing histological images with OCT images acquired by a custom-designed line-scan OCT with high spatial resolution. Although OCT has been widely used in clinical diagnosis, anatomic sources of the OCT bands at the outer retina, particularly the presumed `IS/OS' photoreceptor OCT band, are still controversial. Our experimental result supported conjecture that the presumed `IS/OS' OCT band actually was originated from the IS. The third aim was to characterize a functional biomarker, stimulus-evoked transient phototropism of photoreceptors which was dominant in rods. Functional impairments may precede detectable structural abnormalities. Therefore, functional biomarkers promise early detection of eye diseases. This rod-dominant transient phototropic adaptation provides a specific functional biomarker to evaluate the functional integrity of rod photoreceptors. The last specific aim was to develop an easy, low-cost and phase-artifact free super-resolution method, termed virtually structured detection (VSD), to double the resolution of a confocal point/line scanning system. High resolution imaging is important for reliable identification of structural and functional biomarkers. However, the transverse resolution of conventional imaging systems is fundamentally limited by light diffraction. This dissertation research could not only generate in-depth understanding of intrinsic biomarkers of outer retina but also provide insights into the optimal design of imaging instruments for improved structural and functional assessment of the retina.

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