Abstract
BackgroundThe aim of this study was to investigate the changes in corneal epithelial thickness along the principle meridians of astigmatic corneas after six months of overnight spherical myopic orthokeratology (OK) lens wear.MethodsThis is a prospective study. Fifty-seven subjects with up to 1.50 diopters (D) of corneal toricity wore spherical OK lenses for 6 months. Evaluations of OK lens fit, visual acuity, refractions and corneal toricity (CT) were performed. Fourier-domain optical coherence tomography (FD-OCT) was conducted to measure the corneal epithelial thickness (ET) along the principle meridians of corneal toricity over a diameter of 6 mm. The means of △ET of the same diameter at individual meridians (△ETSm and △ETFm) were calculated and compared.ResultsVisual acuity and refraction improved significantly after OK lens wear. △ETFm thinned more than △ETSm (P = 0.027) at 1.5 mm in radius. △ETSm thickened more than △ETFm at 2.5 mm (P = 0.019) and 3.0 mm (P = 0.036).∣△ETSm - △ETFm∣ were significantly correlated with the baseline central CT at 2.0 mm, 2.5 mm and 3.0 mm. ∣△ETSm - △ETFm∣was significantly correlated with the baseline peripheral CT at 2.5 mm.ConclusionsOvernight wear of spherical OK lenses resulted in differential changes in the thickness profiles of the corneal epithelium between the steep and flat meridians in eyes with corneal toricity.
Highlights
The aim of this study was to investigate the changes in corneal epithelial thickness along the principle meridians of astigmatic corneas after six months of overnight spherical myopic orthokeratology (OK) lens wear
Orthokeratology (OK) is a contact lens technology that results in the temporary correction of myopia using specially designed reverse geometry rigid-gas-permeable (RGP) contact lenses that are worn during sleep
The mean spectacle plane spherical error changed from − 2.77 ± 1.34 Diopters of sphere (DS) at baseline to 0.13 ± 0.50 DS and the mean refractive astigmatism changed from − 0.45 ± 0.32 diopters of cylinder (DC) to − 0.49 ± 0.35 DC
Summary
The aim of this study was to investigate the changes in corneal epithelial thickness along the principle meridians of astigmatic corneas after six months of overnight spherical myopic orthokeratology (OK) lens wear. Orthokeratology (OK) is a contact lens technology that results in the temporary correction of myopia using specially designed reverse geometry rigid-gas-permeable (RGP) contact lenses that are worn during sleep. Modern OK lenses are designed to apply positive pressure over the central cornea and negative pressure in the mid-periphery under the steeper secondary “reverse” curve of the contact lens. In doing so, it produces a flattening of the central corneal treatment zone that corrects the myopic refractive error by reducing the corneal power, and a steepening of the mid-peripheral cornea stabilizing the lens. OK lenses appear to produce their biomechanical changes through thinning of the central corneal
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