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P Soni, T Nguyen; Which Corneal Parameter, Anterior Corneal Curvature, Posterior Corneal Curvature, or Corneal Thickness is Most Sensitive to Acute Changes With Reverse Geometry Orthokeratology Lenses . Invest. Ophthalmol. Vis. Sci. 2002;43(13):3086.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: The purpose of this investigation is to determine which one of the major corneal parameters (anterior corneal curvature, posterior corneal curvature and corneal thickness) is the most sensitive to change under acute application of reverse geometry orthokeratology lenses (OrthoK lenses). Methods: Nineteen, non-selected, eyes were fitted with OrthoK lenses that were on the average 1D flatter than the central horizontal Keratometer reading. The lenses were worn for 60 minutes. Pre and post corneal parameters were evaluated with the Orbscan topographical system and visual acuity was documented using Bailey-Lovie high contrast distance acuity charts. Results: There is significant flattening of central anterior cornea (1.01D, p=0.0003) following lens wear, with a tendency for greater flattening towards the nasal cornea. At 1.5 mm from the center there is no difference between the pre and post corneal curvatures. However significant steepening is noted (nasal -0.95D, p=0.0004; temporal-0.93D, p=0.0077) beyond 2.5 mm both nasally and temporally. In general no significant difference is found in the posterior curvature or corneal thickness following lens wear, except a tendency for cornea to thicken nasally from 1.5 to 3.0 mm (approximately 7µ, P=0.04) is noted. Uncorrected visual acuity on the average improved from 0.603 to 0.428 logMAR units (p=0.0322) following 60 minutes of lens wear. The average reduction in refractive error (0.80D, p, =0.0001) following lens wear correlates well with the anterior corneal curvature change. Conclusion: The anterior corneal curvature is the most sensitive parameter to an acute change induced by a reverse geometry orthokeratology lenses. The refractive error reduction closely parallels the anterior corneal flattening.
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