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Ocular residual astigmatism and topographic disparity vector indexes in normal healthy eyes

Poster Details

First Author: D.Piñero Llorens SPAIN

Co Author(s):    V. Mateo   R. Pérez-Cambrodi   P. Ruiz-Fortes   A. Artola     

Abstract Details


To define a range of normality for the vectorial parameters Ocular Residual Astigmatism (ORA) and topography disparity (TD) and to evaluate their relationship with visual, refractive, anterior and posterior corneal curvature, pachymetric and corneal volume data in normal healthy eyes


Oftalmar, Medimar International Hospital, Alicante, Spain


This study comprised a total of 101 consecutive normal healthy eyes of 101 patients ranging in age from 15 to 64 years old. In all cases, a complete corneal analysis was performed using a Scheimpflug photography-based topography system (Pentacam system Oculus Optikgeräte GmbH). Anterior corneal topographic data was imported from the Pentacam system to the iASSORT software (ASSORT Pty. Ltd), which allowed the calculation of the ocular residual astigmatism (ORA) and topography disparity (TD). Linear regression analysis was used for obtaining a linear expression relating ORA and posterior corneal astigmatism (PCA)


Mean magnitude of ORA was 0.79 D (SD: 0.43), with a normality range from 0 to 1.63 D. 90 eyes (89.1%) showed against-the-rule ORA. A weak although statistically significant correlation was found between the magnitudes of posterior corneal astigmatism and ORA (r=0.34, p<0.01). Regression analysis showed the presence of a linear relationship between these two variables, although with a very limited predictability (R2: 0.08). Mean magnitude of TD was 0.89 D (SD: 0.50), with a normality range from 0 to 1.87 D


Values below 1.9 D for the vector parameters ORA and TD are present in the healthy human eye. The potential diagnostic value of these parameters for the detection of some ocular pathological conditions should be evaluated in future studies

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