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Tsz Wing Leung, Chea-su Kee, Elie de Lestrange; Corneal shape factors are correlated with ocular aberrations in myopes with or without astigmatism. Invest. Ophthalmol. Vis. Sci. 2018;59(9):2130.
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© ARVO (1962-2015); The Authors (2016-present)
Emerging evidence have shown that the human cornea is rotationally asymmetric particularly in the astigmatic eyes. This study aimed to investigate whether the rotationally asymmetric corneal shape is associated with optical aberrations in myopic eyes with or without astigmatism.
Thirty-seven healthy myopic participants with (MA, cylinder ≥2.00DC, axis: ±30°, n=17) or without astigmatism (SM, cylinder ≤0.50DC, n=20) were recruited. The overall (mean-P) and regional corneal shape factors (semi-P) were measured using the Pentacam corneal tomography. The corneal and ocular wavefront aberrations were measured using the i.Profiler plus. The axial biometry was measured using the Lenstar optical biometer.
Consistent with our previous findings, the cornea of MA was more prolate at both the nasal and temporal quadrants (ANOVA repeated measures, between-group effect, Bonferonni post-hoc tests, both p<0.001), and more oblate at the inferior quadrant (p=0.001) than those of SM. Although the magnitudes of ocular and corneal higher-order aberrations did not differ significantly between groups, the mean-P and semi-Ps were significantly correlated with spherical aberrations and comas, respectively, after controlled for the axial length (Partial Pearson’s correlation, r≥0.37, p≤0.03). To understand how the regional corneal shape influenced the peripheral optics, we calculated the off-axis defocuses (±45.0° visual fields in 5°step) using the data of the anterior ocular parameters (corneal curvatures, semi-Ps, and anterior chamber depth) of individual eye based on the Navarro’s eye model. The theoretical modal indicated that due to the more prolate cornea at the nasal and temporal quadrants, the off-axis defocuses in MA were significantly more hyperopic than those in SM across the horizontal visual fields (ANOVA repeated measures, between-group effect, Bonferonni post-hoc tests, all p≤0.001).
The presence of off-axis relative hyperopic defocus has been proposed as a risk factor for myopia development. Whether the presence of rotationally asymmetric cornea contributes to myopia development in children needs further investigation. Our results underscored the contribution of overall and regional corneal shape factors to the ocular aberrations.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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