Validity of pachymetric measurements by manipulating the acoustic factor of Orbscan II

Eye & Contact Lens
Fenghe LuLyndon Jones

Abstract

To assess the validity of pachymetric measurements by examining the constancy of the acoustic factor (AF) of the Orbscan II (Orbtek, Bausch & Lomb, Rochester, NY) after overnight rigid gas-permeable (RGP) contact lens wear. Twenty participants wore CRT (Paragon Vision Sciences, Mesa, AZ) HDS 100 contact lenses on one eye and control lenses on the contralateral eye for one night while sleeping. Another 24 participants wore CRT lenses on both eyes for one night. Central corneal thickness was measured using optical coherence tomography and Orbscan II on the night before lens use, immediately after lens removal on the following morning, and 1, 3, 6, and 12 hours later. By using optical coherence tomography as a reference, the adjusted AF was calculated by using a least squares method over time. The adjusted AF depended on the corneal thickness in normally hydrated corneas. The adjusted AF and the percentage change of the adjusted AF varied before and after overnight lens wear. There was a strong and significant correlation between the corneal swelling and the percentage change of the adjusted AF (all r at least 0.91, P<0.05). The adjusted AF is a variable, not a constant. The AF is a function of the corneal thickness and its altera...Continue Reading

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Feb 28, 2007·Ophthalmic & Physiological Optics : the Journal of the British College of Ophthalmic Opticians (Optometrists)·Sven JonuscheitNorman F Button
Aug 20, 2009·Ophthalmic & Physiological Optics : the Journal of the British College of Ophthalmic Opticians (Optometrists)·Marten F FortuinHenri Kiers
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Jan 16, 2007·Optometry and Vision Science : Official Publication of the American Academy of Optometry·Sven Jonuscheit, Michael J Doughty

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