April 2010
Volume 51, Issue 13
Free
ARVO Annual Meeting Abstract  |   April 2010
Does the Posterior Corneal Elevation Provide the First Indication of Keratoconus?
Author Affiliations & Notes
  • K. C. Baker
    Wang Vision Institute, Nashville, Tennessee
  • Y.-L. Chen
    Univ of Tennessee Space Inst, Tullahoma, Tennessee
  • L. Shi
    Univ of Tennessee Space Inst, Tullahoma, Tennessee
  • J. W. L. Lewis
    Univ of Tennessee Space Inst, Tullahoma, Tennessee
  • L. Kugler
    Wang Vision Institute, Nashville, Tennessee
  • M. Wang
    Wang Vision Institute, Nashville, Tennessee
  • Footnotes
    Commercial Relationships  K.C. Baker, None; Y.-L. Chen, None; L. Shi, None; J.W.L. Lewis, None; L. Kugler, None; M. Wang, None.
  • Footnotes
    Support  R21EY018385; R21EY018935
Investigative Ophthalmology & Visual Science April 2010, Vol.51, 4963. doi:https://doi.org/
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    • Get Citation

      K. C. Baker, Y.-L. Chen, L. Shi, J. W. L. Lewis, L. Kugler, M. Wang; Does the Posterior Corneal Elevation Provide the First Indication of Keratoconus?. Invest. Ophthalmol. Vis. Sci. 2010;51(13):4963. doi: https://doi.org/.

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

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Abstract

Purpose: : The purpose of this study is to examine optical characteristics of keratoconus (KC) and forme fruste keratoconus (FFKC), and investigate whether an irregular shaped posterior cornea is a better indicator than the anterior surface that is often used in KC screening.

Methods: : We included Pentacam data of 18 KC and 22 astigmatic eyes in this study. Within the KC eyes, 8 are mild with manifest best corrected visual acuity (BCVA) of 20/25 or better. The FFKC diagnosis relied on the other eye's condition from the same subject, other KC indications, and family history. The remaining KC eyes are comprised of 5 moderate with a BCVA of 20/30-20/40, and 5 that are worse than 20/40. The 22 astigmatic eyes all had a BCVA of 20/25 or better. The posterior and anterior elevation maps are decomposed into Zernike polynomials to obtain the root mean squared error (RMSE) above the 2nd order that represents high-order complex patterns. The difference between the 2 RMSE values is used as a third indicator. The extreme RMSE values of the astigmatic eyes are used as the screening criteria (i.e. 100% specificity).

Results: : The 7mm diameter cornea decomposition found that the anterior RMSE missed 7 of the 18 KC eyes (61% sensitivity); 5 in the FFKC, 1 in moderate, and 1 in advanced. Both posterior and the RMSE difference missed 4 of the 18 (78% sensitivity); 3 FFKC and 1 moderate KC. The 6mm result shows that the anterior missed 7 of the 18 (61% sensitivity); 5 FFKC, 1 moderate, and 1 advanced. The posterior and the RMSE difference missed 6 of the 18 (67% sensitivity); 5 FFKC and 1 moderate KC. The 5mm result found that the anterior missed 8 of the 18 (56% sensitivity); 5 FFKC, 2 moderate, and 1 advanced. The posterior missed 6 of the 18 eyes (67% sensitivity) and the RMSE difference missed 5 of the 18 (72% sensitivity).

Conclusions: : 1. The posterior cornea surface alone provides more significant indication of keratoconus than the anterior surface. 2. Analysis with a larger cornea area improves detection sensitivity. 3. Either anterior or posterior cornea irregularity is a sufficient indicator of early KC, but sometimes additional information is required to clinically diagnose FFKC.

Keywords: keratoconus • computational modeling • cornea: basic science 
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