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Comparison of corneal shape and biomechanical parameters in normal and very asymmetric ectatic eyes with normal topography

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Session Details

Session Title: Presented Poster Session: Cornea III

Venue: Poster Village: Pod 2

First Author: : M.Sakhaee IRAN

Co Author(s): :    H. Momeni-Moghaddam   M. Sedaghat   B. Lopes   R. Ambrosio Jr     

Abstract Details


To compare and test diagnostic accuracy of corneal shape and biomechanical parameters for distinguishing normal corneas from clinical and subclinical ectasia.


Sedaghat Eye Clinic, Mashhad, Iran.


One eye randomly selected from 74 patients with normal corneas, having no signs of keratoconus comprise the control group. This was compared to both eyes from 24 cases with very asymmetric ectatic (VAE), in which one eye had normal topography exam. Ectasia diagnosis was based on slit-lamp findings and abnormal topographic patterns on the sagittal front curvature map. Corneal biomechanical assessments were done using Corvis ST and Oculus Response Analyzer. Data were analyzed using the Kruskal-Wallis test with post-hot Dunn’s test. Receiver operating characteristic (ROC) curves and the areas under the ROC (AUC) were created to assess diagnostic accuracy.


There were significant differences for all parameters except applanation length 2 (p=0.5). Differences were between all paired groups (NxVAE-E, NxVAE-NT and VAE-E x VAE-NT) for CH, CRF, CBI, BAD-D and TBI. AUC for N x VAE-E and N x VAE-NT were respectively 0.894&0.759 for corneal hysteresis (CH), 0.932&0.842 for corneal resistance factor (CRF), 1.0&0.873 for CBI (corneal biomechanical index), 1.0&0.882 for the BAD-D (Belin/Ambrósio Enhanced Ectasia deviation index).Tomograhic/Biomechanical Index (TBI) had highest accuracy, having a virtually perfect separation from N x VAE-E cases and 91.67% sensitivity and 90.79% specificity, when considering N x VAE-NT.


Biomechanical and tomographic parameters are able to very accurately distinguish normal eyes from ectatic eyes. Considering the topographically normal cornea from VAE eyes, the combination of parameters as the TBI is needed. However, some cases are still normal which is consistent with the concept of unilateral ectasia.

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