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J.T. Barr, P.A. Kusy; Central and Peripheral Keratoconic Corneal Curvature and Depth Changes Induced by Gas Permeable Contact Lenses in Keratoconus . Invest. Ophthalmol. Vis. Sci. 2006;47(13):104.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate the presence and amplitude of curvature and depth changes by GP contact lenses in keratoconus.
The fitting characteristics of KC patients wearing standard design RGP lenses were analyzed with fluorescein and photographed. The subject’s corneal topography was then recorded by the Bausch & Lomb Orbscan II and Medmont E300 topographers. The subjects were then re–fitted with a reverse geometry (XLT) contact lens designed with a wide tertiary curve to align the cornea. The optic zone is elevated above the apex of the cone by a reverse geometry secondary curve. After the subjects had worn the XLT lenses for 1–2 weeks, the fit and topography characteristics were again recorded. The subjects were refitted with an XLT lens if necessary, and characteristics were again analyzed after 1–2 weeks of lens wear. After a stable fit of the KC corneas had been obtained comparative analyses of the data collected was performed.
Topographies, lens curvature, depth, and fitting characteristics were noted. Significant corneal changes were observed in both the central and peripheral corneal areas. The peripheral cornea covered by the wide peripheral curve of the XLT lens generally flattened (0.4–0.2 PCR), and the height of the corneal apex increased (100–150µ) over the 1–2 weeks of lens wear.
Clinicians have long believed that the cornea increases in depth and curvature when a central clearance or vaulting fit is applied to a previously flat fitted keratoconus cornea. These measurements further support this contention.
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