September 2016
Volume 57, Issue 12
Open Access
ARVO Annual Meeting Abstract  |   September 2016
New dynamic corneal biomechanical parameters derived from curvature versus pressure analysis of Ocular Response Analyzer (ORA) data.
Author Affiliations & Notes
  • David Luce
    Ophthalmology, Luce Technical Consulting, Clarence Center, New York, United States
  • Footnotes
    Commercial Relationships   David Luce, Reichert Inc. (P), Reiichert Inc. (C)
  • Footnotes
    Support  none
Investigative Ophthalmology & Visual Science September 2016, Vol.57, 2397. doi:
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      David Luce; New dynamic corneal biomechanical parameters derived from curvature versus pressure analysis of Ocular Response Analyzer (ORA) data.. Invest. Ophthalmol. Vis. Sci. 2016;57(12):2397.

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      © 2017 Association for Research in Vision and Ophthalmology.

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Abstract

Purpose : To present calculation and visualization methods for new and existing corneal biomechanical properties using curvature versus pressure analysis of Ocular Response deformation data.

Methods : Corneal deformation, induced by the ORA air jet, is detected optically, This signal undergoes sign changes, inversion and calibration to provide corneal curvature that is then plotted versus the applied eye pressure.. Energy conversion (to heat) and the dynamic viscoelastic moduli during the 30 msec deformation are explicitly visible in the "hysteresis" loop that is created. Numerical results are calculated from the loop's geometric properties, especially areas of the sub-loops of positive and negative curvature. A Corneal Bending Modulus (CBM) is determined from the slope of the initial curvature following first applanation (zero curvature).
Retrospective ORA data from 34 eyes of 17 subjects from a regular clinical practice and with varied ocular conditions were analyzed.

Results : We report here on statistics for a single parameter, the Corneal Bending Modulus (CBM), the average slope of the pressure/curvature function in a region starting at first applanation and ending before peak pressure and any iris interference. The KC and 4 norm.diverse population's mean/std dev / age is 47 ± 9 yrs. and includes normal, keratoconus, LASIK, INTACS, PRK, PKP subjects. The CV for the CBM between right and left eyes is 26% and 9.`% for unaltered eyes, normal and KC, N=7.

Conclusions : In all cases in the 34 diverse eyes normal eyes have lower compliance than the KC eyes (N=7). In all cases the populations examined here are small. Despite ourconclusions are that there are indications that the technique at using curvature shows significant promise. Muc that justifies continued work. It should be pointed out that the mathematical treatment taken here differs fom the current ORA in that the inversion of the raw ORA data emphasizes the low signal levels regions, the opposite of the current ORA data, The new biomechanical method method extracts informartion during the initinal negative curvature, a unique balance point. In addition any significant interference/with the iris\lens is cleaarly visible and detected.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.

 

Diverse CBM images

Diverse CBM images

 

Figure 2 - Summary of CBM trial results

Figure 2 - Summary of CBM trial results

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