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Errors associated with keratoconus grading using systems based on corneal power

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Session Details

Session Title: Presented Poster Session: Corneal Biomechanics

Session Date/Time: Sunday 06/09/2015 | 09:30-11:00

Paper Time: 10:10

Venue: Poster Village: Pod 4

First Author: : V.Camps Sanchis SPAIN

Co Author(s): :    D. Pinero   E. Caravaca-Arens   A. Artola        

Abstract Details


To analyze and define the possible errors that may be introduced in keratoconus classification when the keratometric corneal power is used in such classification.


University of Alicante


Retrospective study including a total of 44 keratoconus eyes. A comprehensive ophthalmologic examination was performed in all cases, which included a corneal analysis with the Pentacam system (Oculus). Classical keratometric corneal power (Pk), Gaussian corneal power (PcGauss), True Net Power (TNP) (Gaussian power neglecting the corneal thickness effect), and an adjusted keratometric corneal power (Pkadj) (keratometric power considering a variable keratometric index) were calculated. All cases included in the study were classified according to five different classification systems: Alió-Shabayek, Amsler-Krumeich, Rabinowitz-McDonnell, Collaborative Longitudinal Evaluation of Keratoconus (CLEK), and McMahon.


When Pk and Pkadj were compared, differences in the type of grading of keratoconus cases were found in 13.6% of eyes when the Alió-Shabayek or the Amsler-Krumeich systems were used. Likewise, grading differences were observed in 22.7% of eyes with the Rabinowitz-McDonnell and McMahon classification systems and in 31.8% of eyes with the CLEK classification system. All reclassified cases using Pkadj were done in a less severe stage, indicating that the use of Pk may lead to the classification of a cornea as keratoconus, being normal. In general, the results obtained using Pkadj, PcGauss or the TNP were equivalent. Differences between Pkadj and Pc^Gauss were within ±0.7 D.


The use of classical keratometric corneal power may lead to incorrect grading of the severity of keratoconus, with a trend to a more severe grading. The authors have no proprietary or commercial interest in the medical devices that are involved in this manuscript.

Financial Interest:


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