Relationship between Refractive Error and Ocular Shape in Ghanaian Adults
Journal Title: Ophthalmology and Vision Science - Year 2017, Vol 1, Issue 2
Abstract
Background: The peripheral optics of the eye underpins changes in retinal shape associated with refractive errors. This study sought to determine the relationship between ocular shape and refractive error in Ghanaian adults. Method: In this descriptive cross-sectional study, ocular shape was assessed by measuring relative peripheral refractive error (RPRE) of the right eye of 6 myopic, 6 hyperopic and 6 emmetropic adults aged 18 to 25 years as they viewed targets from a distance of 4 meters. Using the Shin-Nippon auto refractor, the relative peripheral refractive error was calculated as the difference between the central spherical equivalent refraction and the peripheral refraction along the horizontal meridian and towards the nasal (N) and temporal (T) regions. The nasal-temporal angles considered in this study were 10º, 20º and 30º giving rise to N10º, N20º, N30º, T10º, T20º and T30º retinal eccentric positions. Data was analysed using Statistical Package for Social Sciences version 20 as well as Excel Statistical Package, and the level of significance was set at a p-value of 5%. Results: Myopic adults showed a relative hyperopic defocus in the peripheral retina, hyperopic eyes had a relative myopic defocus at the periphery and emmetropic eyes had a relatively flat profile. There was nasal-temporal symmetry seen within each refractive error group with p-values of myopia (p = 0.302), hyperopia (p = 0.555) and emmetropia (p = 0.404). Against-the-rule astigmatism increased with increasing retinal eccentricity and there was no significant difference among the refractive error groups’ at all eccentric positions. Oblique astigmatism, however, differed significantly among the refractive error groups at the temporal 30º, eccentric position (p = 0.037) while the other retinal positions showed no statistically significant difference. Conclusion: Adult myopic eyes have a prolate (less oblate) shape, adult hyperopic eyes have a more oblate shape and adult emmetropic eyes have a relatively spherical shape. The findings of this study corroborates other papers in extant literature whilst contradicting others. The need for a flurry of research in this area, using robust methodological approaches, is highly recommended.
Authors and Affiliations
Andrews Nartey, Phyllis Austin, Udeme Aniefiok Obot, Angela Ofeibea Amedo, Nana Yaa Koomson
Keywords
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