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I.G. Stillitano, A. Hofling–Lima, P. Schor, C. Lipener, M.M. Lui, E. Maidana; Wavefront–Guided Corneal Reshaping Analysis . Invest. Ophthalmol. Vis. Sci. 2006;47(13):62.
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© ARVO (1962-2015); The Authors (2016-present)
To analyze wavefront–guided changes of lower–order and higher–order optical aberrations (HOA) after corneal reshaping by overnight orthokeratology (ortho–k) for low to moderate myopia and low myopic astigmatism correction.
Twenty randomly eyes (10 patients) exhibiting sphere from wavefront –1.00D to –3.63D and astigmatism up to –1.59D were prospectively analyzed during pre–test and after 1, 8, 30, 90 nights of customized ortho–k lens therapy (Be Free, Mediphacos Ltda, Belo Horizonte, Brazil). Wavefront measurements of lower and HOA derivate into Zernike polynominals were determined for pupil size of 6.5 mm and performed by the LADARWave Shack–Hartmann aberrometer (Alcon Laboratories). Optical aberrations were quantitatively analyzed using RMS (root mean square) coefficient values. Data on sphere, cylinder, defocus, total RMS, HOA RMS, spherical aberration and total coma (T–coma), horizontal (H–coma) and vertical coma (V–coma) were collected.
Ortho–k significantly reduced the mean sphere refraction from wavefront: –2.04±0.76D (baseline) to +0.34±0.74D (180 nights) (P<0.0001, paired t test). The main change occurred between 1 and 8 nights follow–up (–1.17±0.17D). The mean cylinder did not changed. Total RMS and defocus continued decreasing up to 90 nights. HOA RMS increased up to 8 nights from 0.39±0.10µ to 1.04±0.27µ but did not significantly changed between 30 and 90 nights. T–coma increased 2.0–fold. H–coma increased up to 8 nights to the positive direction in the right eyes and to the negative direction in the left eyes and remained unchanged. V–coma fluctuated significantly to the negative direction in both eyes. Spherical aberration increased 10.0–fold up to 8 nights and remained unchanged (p<0.05).
Wavefront–guided ortho–k with Be Free was found to be effective and stable after 8 nights for HOA, particularly coma and spherical aberration. The lower–order optical aberrations continued decreasing during 90 nights follow–up. Wavefront analysis made it possible to map a profile of the whole eye during ortho–k corneal reshaping.
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