May 2003
Volume 44, Issue 13
Free
ARVO Annual Meeting Abstract  |   May 2003
Use of Elevation Topography in Rigid Gas Permeable Lens Fitting of Keratoconus
Author Affiliations & Notes
  • S.M. Lee
    Ophthalmology, Univ of CA San Francisco, San Francisco, CA, United States
  • S.D. McLeod
    Ophthalmology, Univ of CA San Francisco, San Francisco, CA, United States
  • D.G. Hwang
    Ophthalmology, Univ of CA San Francisco, San Francisco, CA, United States
  • Footnotes
    Commercial Relationships  S.M. Lee, None; S.D. McLeod, None; D.G. Hwang, None.
Investigative Ophthalmology & Visual Science May 2003, Vol.44, 1309. doi:
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    • Get Citation

      S.M. Lee, S.D. McLeod, D.G. Hwang; Use of Elevation Topography in Rigid Gas Permeable Lens Fitting of Keratoconus . Invest. Ophthalmol. Vis. Sci. 2003;44(13):1309.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Abstract: : Purpose: To determine the utility of scanning-slit elevation topography data for rigid gas permeable contact lens curvature selection in keratoconus. Methods: We obtained scanning-slit elevation data for 17 eyes of 12 patients with clincal keratoconus. We obtained the following values: average sim K, axial apical curvature, tangential apical curvature, and total mean curvature. We compared this data to the base curves of contact lenses fit using a minimal apical clearance philosophy. Results: Mean contact lens base curve for all patients was 48.71 +/- 3.84D. This value was significantly different (p<0.01) from axial apical (54.14 +/- 6.56D), tangential apical (58.37 +/- 7.17D), and mean power (52.68 +/- 6.49D) values. For mild cones (with sim K values <50D, n=9), the mean contact lens base curve was 46.27 +/- 2.21D. There was again a statistically significant difference (p<0.01) between this curvature and the three map-derived curvatures; axial (49.90 +/- 3.86D), tangential (54.04 +/- 3.70D), and mean curvature (49.02 +/- 2.34D). In the subgroup of moderate to advanced cones (any sim K value >50D, n=8), the mean base curve was 51.44 +/- 3.46D. There was some correlation with the mean curvature power (56.79 +/- 7.30, p=0.02), but no significant correlation with axial (58.91 +/- 5.66D) and tangential (62.84 +/- 7.67D) curvatures. Conclusions: Scanning-slit topography provides a representation of corneal surfaces independent of axial biases. Although mean curvature maps, based on scanning-slit data, resembled elevation float maps, the apex curvature derived from these displays were consistently steeper than acutal contact lens base curves. Therefore, scanning-slit topography does not appear to provide direct predictive value in base curve selection for keratoconus patients.

Keywords: contact lens • keratoconus • topography 
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