Peripheral retinal characteristics have been shown recently to have an influence upon refractive error development, specifically myopia. Studies of peripheral refraction have shown that emmetropic subjects typically display a myopic peripheral refraction, whereas myopic subjects have been found to have relative hyperopic refraction in the periphery. Myopic and hyperopic subjects were recruited for the experiments detailed in this thesis, from the student population at Glasgow Caledonian University. Previous studies on human subjects have generally made comparisons between myopic and emmetropic subject groups. Our study will contribute significantly to the knowledge in this area by extending the investigations to include hyperopic subject groups. Our results show significant differences in peripheral retinal shape between hyperopic and myopic subjects. Peripheral retinal shape in hyperopia shows symmetry between the temporal and nasal retina. In contrast, the myopic subjects show significant asymmetry between temporal and nasal retinal shape (Chapters 4 and 5). We also show that eye rotation significantly alters peripheral retinal shape in myopic subjects but not in hyperopic subjects. These findings indicate structural differences between myopic and hyperopic eyes worthy of further investigation. Monochromatic higher order aberrations (MHOA) were investigated in myopic and hyperopic subjects. Analyzed Zernike coefficients of the third, fourth and fifth orders show the myopic and hyperopic subjects display a similar profile. Interestingly when the lens is forced to either relax as a result of the instillation of cyclopentolate hydrochloride (Chapter 7) or accommodate (Chapter 6) the MHOA are significantly altered. The most significant change is seen in the fourth order spherical aberration. This work has identified significant structural and internal differences between subjects with myopia and those with hyperopia thus giving further insight into the optical and physical differences that exist between the myopic and hyperopic eye. With hyperopic eyes often displaying a stable refractive error and rarely going on to develop myopia the key to investigating myopic development may be further investigation of hyperopia and any differences that may exist.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:606549 |
| Date | January 2013 |
| Creators | Macfadden, Lucy |
| Publisher | Glasgow Caledonian University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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