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T. Hiraoka, C. Okamoto, Y. Ishii, F. Okamoto, T. Oshika; Recovery of Corneal Irregular Astigmatism, Ocular Higher-Order Aberrations, and Contrast Sensitivity After Discontinuation of Overnight Orthokeratology. Invest. Ophthalmol. Vis. Sci. 2008;49(13):4845.
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Overnight orthokeratology has been reported to increase corneal irregular astigmatism and ocular higher-order aberrations, and reduce contrast sensitivity function. It remains unknown, however, whether these changes completely recover after discontinuation of orthokeratology. We conducted the current 13-month prospective study to address this question.
Thirty-four eyes of 17 subjects who underwent overnight orthokeratology for 12 months were included in the study. Their mean age was 23.9 ± 3.5 years (mean ± standard deviation). Manifest refraction, corneal topography, wavefront aberrometry, high-contrast visual acuity test, and contrast sensitivity test were performed at baseline, 12-month after commencement of the procedure, and 1 week and 1 month after discontinuation of the treatment. Asymmetry and higher order irregularity components were calculated in the central 3-mm zone by using Fourier analysis of the corneal topography data. Ocular higher-order aberrations for a 4-mm pupil were measured, and the root-mean-square (RMS) of the third- and fourth-order aberrations was determined. Contrast sensitivity was assessed at four spatial frequencies, and the area under the log contrast sensitivity function (AULCSF) was calculated.
Overnight orthokeratology significantly reduced manifest spherical equivalent refraction (P < 0.0001, paired t-test), and significantly improved uncorrected visual acuity (UCVA) at 12 months after commencement of the procedure (P < 0.0001). Asymmetry and higher order irregularity components significantly increased (P < 0.0001, P = 0.0045, respectively), and third- and fourth-order RMS of wavefront aberration also significantly increased after the procedure (P < 0.0001). The treatment resulted in significant decreases in AULCSF (P = 0.0033). After discontinuing lens wear, asymmetry component, higher order irregularity component, third-order RMS, fourth-order RMS, and AULCSF fully returned to the baseline level within 1 week. Spherical equivalent and UCVA recovered to the pre-treatment level at 1 month after ceasing orthokeratology.
The current study confirmed that the effect of overnight orthokeratology is completely reversible in light of optical quality of the eye and quality of vision as well as refraction and visual acuity. The full recovery of corneal irregular astigmatism, ocular higher-order aberrations, and contrast sensitivity was faster than that of refraction and UCVA.
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