July 2019
Volume 60, Issue 9
Open Access
ARVO Annual Meeting Abstract  |   July 2019
Clinical Measurement of Posterior Corneal Astigmatism in Normal Corneas
Author Affiliations & Notes
  • George Asimellis
    Kentucky College of Optometry, University of Pikeville, Pikeville, Kentucky, United States
  • Footnotes
    Commercial Relationships   George Asimellis, None
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Investigative Ophthalmology & Visual Science July 2019, Vol.60, 593. doi:
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      George Asimellis; Clinical Measurement of Posterior Corneal Astigmatism in Normal Corneas. Invest. Ophthalmol. Vis. Sci. 2019;60(9):593.

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

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Purpose : Clinical evaluation of total and posterior corneal astigmatism in healthy eyes using a Scheimpflug imaging device and a novel, color-coded Light-Emission-Diode corneal topographer.

Methods : Data analysis of 60 healthy, unoperated, non-contact lens wearer eyes. A Scheimpflug imaging device (Pentacam HR, Oculus Optikgeräte GmbH, Wetzlar, Germany) and a novel, color-coded Light-Emission-Diode (LED) spot reflection corneal topographer (Cassini, iOptics, Netherlands) were employed in this study. The Cassini is employing a non-rotationally symmetric projection pattern emanating from nearly seven hundred distinct LED color-coded (red, yellow and green) spots. Facilitated by Purkinje imaging and specular reflection-based shape reconstruction of both the anterior (1st Purkinje image) and the posterior (2nd Purkinje image) corneal surface, the Cassini also produces posterior astigmatism measurements. Repeatability of posterior keratometry measurements was evaluated between pairs of devices with Bland-Altman plots and 95% confidence intervals. Repeatability was defined as the difference between the upper/lower limits of agreement and the mean.

Results : The repeatability of measurement of the posterior keratometry was for the Pentacam device 0.27 D, and for the Cassini 0.39 D. The mean difference in average posterior keratometry, between the Cassini and the Pentacam was -0.15 D (p=0.006). Bland-Altman plot is provided in Figure 1.

Conclusions : The clinical diagnostics available to the cornea investigator today that produce total cornea power calculation may not be fully optimized. Current anterior-segment imaging provides clinical options that appear to produce similar readings and acceptable repeatability, under proper acquisition protocols.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.



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