PMID: 8587767Nov 1, 1995Paper

Accuracy of videokeratography for instantaneous radius in keratoconus

Optometry and Vision Science : Official Publication of the American Academy of Optometry
J S ChanR E Fusaro

Abstract

Present videokeratographs provide corneal radius of curvature measurements in terms of axial (sagittal) radius and, for some instruments, instantaneous (tangential) radius. The EyeSys videokeratograph allows conversion from axial to instantaneous radius based on an algorithm, which assumes a basic corneal shape of elliptical form. We tested the accuracy of the EyeSys instantaneous radius algorithm for 29 keratoconic corneas using the criterion that instantaneous radius of the cone apex could be determined accurately by aligning the cone apex with the optic axis of the videokeratoscope. There was a close relation between the instantaneous values obtained from the regular and apex alignments for the 17 eyes with cone apices below 55 D (95% limits of agreement -0.39 to 1.49 D), but not for the 12 eyes above 55 D (95% limits of agreement -4.87 to 6.61 D). The mean distance of the cone position from the center of the map was 1.16 mm for the instantaneous map and 1.59 mm for the axial map. Assuming the criterion for accuracy to be the corneal radii found when the videokeratograph was aligned with the cone apex, the instantaneous map for the EyeSys videokeratograph at regular alignment provided reasonably valid measurements for cornea...Continue Reading

Citations

Nov 15, 2005·Eye & Contact Lens·Loretta Szczotka-Flynn, Binoy R Jani
Aug 17, 2012·Journal of Biomedical Optics·Jinglu YingMingguang Shi
Feb 23, 2000·Journal of Cataract and Refractive Surgery·G U AuffarthH E Völcker
Feb 24, 2016·Eye and Vision·F Cavas-MartínezD G Fernández-Pacheco
Oct 31, 2012·Journal of Cataract and Refractive Surgery·Shyam Sunder TummanapalliVirender S Sangwan
Dec 1, 2012·Journal of Cataract and Refractive Surgery·David P PiñeroAlberto Lopez-Miguel
Feb 5, 2010·Contact Lens & Anterior Eye : the Journal of the British Contact Lens Association·Luigina Sorbara, Kristine Dalton
Dec 26, 2015·Journal of Cataract and Refractive Surgery·Shyam Sunder TummanapalliVirender S Sangwan
Nov 4, 2006·Journal of Cataract and Refractive Surgery·William J Dupps
May 13, 2017·Contact Lens & Anterior Eye : the Journal of the British Contact Lens Association·Stefan BandlitzJames Wolffsohn
Aug 29, 1997·Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences·A Pentland
Jan 15, 2003·Current Eye Research·Achim LangenbucherBerthold Seitz

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