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Anterior irregularity characterization by means of new placido-based indices: a preliminary study in keratoconus and subclinical keratoconus patient

Poster Details

First Author: A.Vega-Estrada SPAIN

Co Author(s):    D. Ramos L   A. Martinez Finkelsntein   G. Castro de Luna   N. Burguera Gimenez   D. Pi   J. Alio

Abstract Details


To assess the performance of a set of new topographic indices computed directly from the digitized images of the Placido rings in a sample of normal, keratoconic and keratoconus suspect eyes.


Department of Statistics and Applied Mathematics, Almerķa University, Institute Carlos I of Theoretical and Computational Physics, Vissum Corporation, Almerķa, Keratoconus Unit. Vissum Corporation, Alicante, Departament of Optic, Farmacology and Anatomy, University of Alicante, Division of Ophthalmology, Universidad Miguel Hernįndez, Alicante, Spain.


136 consecutive eyes of 102 patients were divided into three groups depending on the presence or not of keratoconus: control group, 62 eyes, keratoconus group, 50 eyes and keratoconus suspect group, 24 eyes. In all cases, a comprehensive examination was performed including the corneal topography with a Placido-based CSO topography system. Clinical outcomes were compared among groups, along with the discriminating performance of the proposed irregularity indices, which were derived directly from the digitized images of the Placido rings on the cornea.


Significant differences were found when comparing the values of the indices among groups. Statistical methods such as the Witney-Wilcoxon non-parametric test, the Fisher’s test, receiver operating characteristic analysis and the K-fold cross-validation showed the capability of the indices to discriminate between normal (p?0.01), keratoconus (p?0.01) and keratoconus suspect eyes (p?0.01).


Direct analysis of the digitized images of the Placido mires projected on the cornea is a valid and effective tool for keratoconus diagnosis. Although based only on the data from the anterior surface of the cornea, the classifying ability of the new indices turned out to be very good, even in the difficult task of detecting keratoconus suspect eyes. These indices can be used as supplementary criteria for diagnosing and grading keratoconus, to add on to the current keratometric classifications. FINANCIAL DISCLOSURE?: No

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