Role of genetics in susceptibility to environmentally-induced myopia

Chen, Yen-Po 2011. Role of genetics in susceptibility to environmentally-induced myopia. PhD Thesis, Cardiff University.

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Abstract

Myopia is a common ocular disorder with complex and yet unidentified causes. Studies in animal models of myopia have revealed substantial variation in the degree of myopia induced by a uniform regimen of visual manipulation. This study investigated the role of genetics on susceptibility to environmentally-induced myopia by means of a selective breeding experiment. Chicks with high or low susceptibility to monocular form deprivation (FD) were selected from an outbred population that showed considerable variation in the response to FD. After two rounds of selection, the High and Low susceptibility selected lines exhibited an evident divergence in their ocular responses to FD. Chicks from the High line developed twice the degree of myopia compared to those from the Low line. This difference was not due to visual disability or immaturity of the visual system in Low line chicks. Thus, susceptibility to form deprivation in chicks has a strong genetic component. In estimating the heritability, approximately 50% of the variation in the chicks' susceptibility to FD-induced myopia was attributable to additive genetic effects. However, the genetic variants that control the normal variation in eye size appear to be distinct from the variants that determine susceptibility to FD due to no evidence of pleiotropic genetic effects between these traits. When chicks from the High and Low lines were tested for their responses to lens- induced visual defocus, a significant difference between the two selected lines was observed for minus lens wear, but not for plus lens wear. Thus, there must be some shared mechanism(s) in the ocular responses to FD and minus lens wear, but different mechanisms in the responses to plus lens wear and FD. Compared to the chicken, the mouse model of myopia has the advantages of a closer evolutionary relationship to humans and features of primate myopia. Using a novel swept-source OCT system, it was found that OCT showed good repeatability and accuracy in measuring axial ocular components in mouse. In addition, axial ocular components in mice were found to be mainly controlled by additive genetic effects.

Item Type:	Thesis (PhD)
Status:	Unpublished
Schools:	Optometry and Vision Sciences
Subjects:	R Medicine > RE Ophthalmology
ISBN:	9781303219092
Date of First Compliant Deposit:	30 March 2016
Last Modified:	15 Jan 2024 15:27
URI:	https://orca.cardiff.ac.uk/id/eprint/55049

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