All ETDs from UAB

Advisory Committee Chair

Thomas T Norton

Advisory Committee Members

Xiangqin Cui

Alecia K Gross

Joanne E Murphy-Ullrich

Steven J Pittler

Document Type

Dissertation

Date of Award

2009

Degree Name by School

Doctor of Philosophy (PhD) School of Optometry

Abstract

During the juvenile period of human development, an emmetropization mechanism uses visual signals to precisely guide the axial length elongation rate of the eyes to the optical power to keep the images in sharp focus. However, almost a third of the U.S. population develops axial myopia, in which the eye is elongated relative to the focal plane. The aims of the study were to examine 27 genes and 6 proteins in tree shrew sclera for potential differential expression patterns during minus lens compensation and dur-ing recovery. The study hypothesized that, in response to hyperopia produced by a -5 D lens, specific molecules initiate and participate in ECM remodeling, which raises the scleral creep rate and increases the rate of axial elongation; and during recovery, some of the same molecules produce a reversed pattern mRNA, while other molecules are activated or return to normal such that the scleral creep rate is decreased and the axial elongation rate is slowed in response to the myopia that occurs when the -5 D lens is removed. Overall, nineteen of the genes showed differential changes in mRNA levels. Besides all three TGF-beta isoforms and the three receptor subtypes, six matricellular proteins, THBS-1 and 2, TNC, SPARC, SPP1 and TGFBI also showed differential mRNA changes. Among them, THBS1 also showed positive correlation between the differential mRNA and protein levels. Changes in MT1-MMP and TIMP3 confirmed results of previous studies, but the possible involvement of ADAMTS 1 and 5 were new results involving matrix metalloproteinases. In general, this study showed that scleral fibroblasts differentiate between retinal "go" signals and retinal "stop" signals. This suggests that differential responses by the scleral fibroblasts contain important information about how scleral remodeling occurs during minus lens compensation and recovery. A signature of changes in gene expression that characterizes changes during compensation and recovery may help us to understand whether the sclera responds similarly to all types of "go" signals received from the retina, and if it responds similarly to all types of "stop" signals even when the visual stimulus producing those signals is different.

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Optometry Commons

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