Spherical aberration and corneal asphericity in different grades of myopia
Journal Title: Medpulse International Journal of Ophthalmology - Year 2017, Vol 4, Issue 1
Abstract
Purpose: The objective of this study was to find any possible relationship between spherical aberration, corneal asphericity and degree of refractive error using Hartmann- Shack’s aberrometry and Placido disc based corneal topography. Materials and Methods: 100 eyes of fifty healthy individuals aged between 18 and 34 years were recruited. We excluded all subjects with best corrected visual acuity less than 20/20, any systemic disease or any ocular pathology. All subjects underwent auto-refractometer measurement followed bysubjective refraction and acomprehensive ocular examination. Optical aberration and corneal asphericity of each subject were measured using Hartmann- Shack’s aberrometry and Placido disc based corneal topography. Subjects were divided into three refractive error groups [1] mild myopes - Spherical Equivalent [SE] < 3D [2] moderate myopes - SE between -3D to -6D and [3] high myopes SE ≥ -6D. Data were statistically evaluated using ANOVA. Results: There was a statistically significant negative correlation between spherical aberration and corneal asphericity (P value <0.01). The mean value of Spherical Aberration in mild myope was -0.190±.32 microns, moderate was -0.167±.19 microns and high myope was -0.107±.17 microns. There was a statistically significant increase in spherical aberration at moderate myopic group compared to mild myopic group (P value < 0.030). Mean value of Corneal Asphericity (Q Value) of mild myopic group was -0.416±.15, moderate myopic group was -0.336±.16 and High myopic group was -0.4313±.07 corneal asphericity for the high myopic group was significantly more than that of mild and moderate myopic groups (P value < 0.05). Mean value of higher order aberration in mild myopic group was 0.224±.14 moderate myopic group was 0.2286±.14 and for high myopic group was 0.302±.14. Higher order aberration was increased with degree of refractive error but it was not statistically significant. Conclusion: In this study, there was statistically significant negative correlation between spherical aberration and corneal asphericity, indicating that more prolate the cornea, less the amount of spherical aberration. The degree of corneal asphericity was seen to be higher in high myopes.
Authors and Affiliations
Anil Radhakrishnan, Aswathy V M
Keywords
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