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T. Hiraoka, C. Okamoto, F. Okamoto, Y. Ishii, Y. Hirohara, T. Mihashi, T. Oshika; Influence of Decentered Treatment of Orthokeratology on Ocular Higher-Order Wavefront Aberrations. Invest. Ophthalmol. Vis. Sci. 2007;48(13):5383.
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To investigate the relation between decentration of corneal central flattened area after orthokeratology and ocular higher-order wavefront aberrations.
Subjects were 46 eyes of 23 patients undergoing overnight orthokeratology for myopia. Mean age was 24.2 ± 3.3 years (range 21 to 33), and mean spherical equivalent before treatment was -2.38 ± 0.98 D (range -1.00 to -4.00). Decentration of central flattened area was determined by computerized videokeratography (TMS-4, Tomey). On the instantaneous power map at 3-month follow up visit, sixteen points were plotted along an equi-refractive-power line surrounding the central flattened area. On the basis of these plotted points, an approximate ellipse and its center were determined using a data analysis software (MATLAB®, Cybernet systems). The degree of decentration was calculated as the distance between the center of the ellipse and the center of the entrance pupil. Simultaneously, ocular higher-order aberrations for a 4-mm pupil were measured using the Hartmann-Shack aberrometer (KR-9000PW, Topcon), and the relationship between the decentration and higher-order aberrations was analyzed.
The decentration was 0.85 ± 0.51 mm (range 0.17 to 2.05), which significantly correlated with 3rd order aberration (RMS) (Pearson, r=0.662, p<0.0001) and 4th order aberration (RMS) (r=0.566, p<0.0001). The decentration also showed significant correlation with the amount of myopic correction (r=0.332, p=0.0269).
The larger the decentration of orthokeratology treatment was, the greater the induction of ocular higher-order aberrations was. These changes depended on the amount of myopic correction. For better optical quality of the eye, the fitting and centration of the treatment lens should be strictly performed, and large myopic correction should be avoided in orthokeratology practice.
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