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First Author: L.Jordao BRAZIL
Co Author(s): I. Ramos F. Faria-Correia B. Lopes B. Valbon M. Salomão R. Ambrósio Jr.
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To test a new combination of pachymetric parameters from corneal tomography to distinguish normal from ectatic corneas.
Instituto de Olhos Renato Ambrósio, Rio de Janeiro-RJ, Brazil; Rio de Janeiro Corneal Tomography and Biomechanics Study Group, Rio de Janeiro-RJ, Brazil.
One eye randomly selected from 204 normal patients (Group N), one eye randomly selected from 177 cases of bilateral keratoconus (Group KC), and 112 eyes with normal front surface topography from cases with keratoconus in the fellow eye (Group Forme Fruste of Keratoconus-FFKC) were included. The Pentacam-HR provided pachymetric parameters: thinnest point (TP), vertical dislocation from apex of the TP, pachymetric progression indexes at maximal meridian (PPI Max) and the average of all meridians (PPI Ave). Fisher linear discriminant analysis was used to optimize a combination of these parameters to provide best possible separation between normal and ectatic corneas.
The combined parameter, named "Advanced Ambrósio"s Relational Thickness" (Adv.ART) obtained 91.07% of sensitivity and 92.65% of specificity to distinguish N and FFKC (AUC = 0.963) and 98.9% of sensitivity and 99.5% of specificity to separate N and KC (AUC=0.999). Considering normal and ectatic corneas (KC + FFKC), Adv.ART had 95.16% of sensitivity, 94.61% of specificity and AUC of 0.985. The AUC from Adv.ART was statistically superior (p<0.005) than AUC from each parameter individually.
Combination of pachymetric parameters effectively distinguish normal and ectatic corneas. Adv.ART provide a virtually perfect separation between normal corneas from keratoconus, and enhances the sensitivity for milder forms of ectasia, such as in cases considered as forme fruste keratoconus.