Objective To investigate corneal biomechanical differences in different geometric design parameters of orthokeratology lenses(OK lenses)and to further reveal the corneal shaping mechanism of OK lenses.Methods A coupled finite element model of the aspheric OK lens corneosclera was established for various geometric design parameters of the OK lens,corresponding to different degrees of myopia correction.The distribution trends of the profile and curvature of the corneal anterior surface,as well as the von Mises stress(VMS)and eye axis displacement on both the corneal anterior surface and superior corneal stroma surface were analyzed numerically.Results The stress concentration of the corneal anterior surface was observed in the mid-peripheral and peripheral zones,whereas that of the superior corneal stroma surface appeared in the mid-peripheral zones.The sagittal height of the base curve of the OK lens decreased with increasing degree of myopia correction.At myopia correction degrees of-2.0,-3.0,-4.0,-5.0,and-6.0 D,the maximum corneal VMS increased by 0.81%,1.86%,2.84%,3.81%,and 7.04%,respectively,compared with that at-1.0 D;the curvature of the corneal central zone was reduced by an average of 2.59,3.78,4.51,4.99,5.33,and 6.41 D compared with that without OK lenses.Conclusions The sagittal height of the base curve of the OK lens decreased with increasing degree of myopia correction,resulting in a flatter central curvature of the cornea.The base curve of the OK lens plays a crucial role in both correction and control of myopia.
corneal biomechanicsorthokeratology lensmyopia correction degreecorneal shapingfinite element analysis
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NSTL
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