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J. Tsukiyama, Y. Miyamoto, S. Higaki, M. Fukuda, Y. Shimomura; Changes in the Anterior and Posterior Radii of the Corneal Curvature and Anterior Chamber Depth by Orthokeratology. Invest. Ophthalmol. Vis. Sci. 2007;48(13):5384.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate the mechanism for the refractive effect of orthokeratology using measurements of the anterior and posterior radii of the corneal curvature and anterior chamber depth with PentacamTM analysis system.
Subjects were 9 women (18 eyes, mean age 29.6±3.8 years) with low to moderate myopia. All subjects were recruited to a 53-week trial of overnight orthokeratology using RD-171K lens (hexafoconA). After wearing orthokeratology lenses overnight, subjects were examined at daytime. With PentacamTM analysis system, subjects were examined in 2, 4, 8, 12, 24, 36, and 53 weeks for the assessment of the anterior and posterior radii of the corneal curvature and the anterior chamber depth.
Myopic refractive error significantly reduced (ANOVA, p<0.001). The refractive error was -2.85±0.46D at the base line and significantly reduced to -0.28±0.65D in 2 weeks (Bonferroni/Dunn post-hoc test, p<0.01). A significant correlation was observed between the amount of change in central anterior radius of corneal curvature and the change in the refractive error at the 24 weeks (Pearson correlation coefficient, r=0.57, p<0.05). However, in any weeks, no significant differences were seen in either the central posterior radius of corneal curvature (ANOVA, p=0.55) or the anterior chamber depth (ANOVA, p=0.69).
Overnight orthokeratology lens wear alters the anterior corneal shape rather than the posterior radius of corneal curvature and the anterior chamber depth. This suggests that the primary factor behind the refractive effect of orthokeratology is change in the anterior corneal shape rather than the overall corneal bending.
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