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Both animal and human studies have demonstrated that the peripheral retina influences central refractive error development. It is hypothesised that peripheral hyperopic defocus may act as a strong stimulus for axial eye elongation. However, conflicting reports have been published suggesting no influence of peripheral refraction on human central refractive error development. Therefore, the role of the peripheral retina on myopia development in human eyes is yet to be understood. Interestingly, optical treatments that have been developed to induce peripheral myopic defocus using peripheral add power have been found to show some myopia control effects, indicating peripheral refraction may play a role in myopia development. Currently, orthokeratology (OK) is considered as the most effective optical treatment for myopia control. It is hypothesised that mid-peripheral corneal steepening may induce peripheral myopic defocus changes in myopic eyes treated with conventional OK lenses. However, there is large variability in myopia control outcomes with OK treatment which may be due to differences in ocular shape and peripheral refraction among individuals. Attempts to individualise peripheral optical defocus changes through manipulation of anterior corneal shape using OK lens designs are tedious and time consuming. Instead of manipulating the anterior corneal shape, this thesis aims to use large diameter (LD) rigid lenses as a novel optical model to induce peripheral defocus changes by anterior contact lens surface manipulations to mimic the OK optical treatment effect. However, before manipulating the front surface profile of these LD contact lenses, there was a need to understand the fitting aspects of LD contact lenses.To investigate the fitting aspects of LD contact lenses, the CASIA swept source (SS) anterior segment optical coherence tomographer (OCT) was used extensively in the research studies reported in this thesis. It has been reported previously that OCT instrumen

The aims of this thesis were to investigate peripheral refraction in different refractive groups and verify the use of peripheral refraction as a measure of ocular shape. Furthermore, manipulation of peripheral refraction with orthokeratology (OK) and soft contact lenses (SCLs) for potential myopia control were explored. Characteristic peripheral refraction profiles were measured using the Shin-Nippon NVision-K 5001 autorefractor in emmetropes (relative peripheral myopia) and myopes (relative peripheral hyperopia). East Asian moderate myopes had greater amounts of relative peripheral hyperopia compared to Caucasians with a similar central refractive error. This was interpreted to reflect a more prolate ocular shape in the myopic Asian eye.Calculated axial length from peripheral refraction was found to comparable to direct axial length measurements with the IOLMaster in the nasal retina and to underestimate axial length in the temporal retina. Although not entirely comparable, peripheral refraction is still able to give information on the shape of eyes with different refractive errors.Conventional corrections of central myopia induce hyperopia onto the peripheral retina. However, OK lenses were found to cause a hyperopic shift in the central visual field (VF) in both myopic children and adults. This caused peripheral refraction which was initially relatively hyperopic to become relatively myopic compared to the central refraction. Furthermore, changing the optic zone diameter or steepening the periphery of the OK lens was found to cause no significant effect. Relative hyperopic peripheral refraction was measured along the horizontal VF with under (+0.75DS), full, over (-0.75DS) SCL correction and multifocal SCLs with a distance centre and plus power (+2.00) periphery were found to induce less peripheral hyperopia compared to single vision (SV) SCL correction. OK allows the peripheral retina to experience myopic defocus while central myopia is corrected, and multifoca