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J. Wu, Q. Yu, H. Zhang, L. Zhang, S. Ye, S. Dong, C. Zhang, J. He; Wavefront Analysis of the Effect of Corneal Surface Shape on On-Eye RGP Contact Lenses. Invest. Ophthalmol. Vis. Sci. 2009;50(13):1569.
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The shape of anterior corneal surface of the human eye is irregular, and the irregularity has been recently analyzed and precisely described as wavefront aberrations. Purpose of this study is to investigate effect of the corneal irregularity on on-eye RGP contact lens.
Corneal topography was taken for 46 bare eyes of 23 subjects before RGP lens use, and corresponding wavefront aberrations of the anterior corneal surface (up to 7th order Zernike aberrations) was derived with a MatLab program. Wavefront aberrations of the anterior surface of on-eye RGP contact lenses in the 46 eyes was also measured by taking corneal topography again for the same 46 eyes with the RGP contact lenses on-eye after one month wearing of the RGP contact lenses. Zernike aberrations of the RGP contact lenses were examined and also correlated to those of base-line anterior corneal surface.
For bare eyes, mean base-line corneal Zernike aberrations for about half of the 12 terms (2nd to 4th orders) were significantly different from zero. For on-eye RGP CL, three mean Zernike aberrations were observed to be significant, these were defocus (C4, 1.05µm, p=0.01, OD; 1.07µm, p=0.001, OS), main axis astigmatism (C5, -0.27µm, p<0.001, OD; -0.32µm, p<0.001, OS), and spherical aberration (C12, 0.29µm, p<0.001, OD; 0.30µm, p<0.001, OS). The astigmatism of on-eye RGP CL was significantly correlated to that of bare eye (r=0.63, p=0.001).
The results suggest that surface shape of on-eye RGP CL is not rigid, and its change depends on irregularity of the anterior corneal surface.
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