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KMID : 1011420120170020223
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Journal of Korean Ophthalmic Optics Society
2012 Volume.17 No. 2 p.223 ~ p.232
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Validating a New Approach to Quantify Posterior Corneal Curvature in Vivo
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Yoon Jeong-Ho
Kodikullam Avudainayagam
Chitralekha Avudainayagam
Helen A Swarbrick
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Abstract
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Purpose: Validating a new research method to determine posterior corneal curvature and asphericity(Q) in vivo,
based on measurements of anterior corneal topography and corneal thickness.
Methods: Anterior corneal topographic data, derived from the Medmont E300 corneal topographer, and total corneal thickness data measured along the horizontal corneal meridian using the Holden-Payor optical pachometer, were used to calculate the anterior and posterior corneal apical radii of curvature and Q. To calculate accurate total corneal thickness the local radius of anterior corneal curvature, and an exact solution for the relationship between real and apparent thickness were taken into consideration. This method differs from previous approach.[18,27-30] An elliptical curve for anterior and posterior cornea were calculated by using best fit algorism of the anterior corneal topographic data and derived coordinates of the posterior cornea respectively. For validation of the calculations of the posterior corneal
topography, ten polymethyl methacrylate (PMMA) lenses and right eyes of five adult subjects were examined.
Results: The mean absolute accuracy (±standard deviation(SD)) of calculated posterior apical radius and Q of
ten PMMA lenses was 0.053±0.044 mm (95% confidence interval (CI) ?0.033 to 0.139), and 0.10±0.10 (95% CI ?0.10 to 0.31) respectively. The mean absolute repeatability coefficient (±SD) of the calculated posterior apical radius and Q of five human eyes was 0.07±0.06 mm (95% CI ?0.05 to 0.19) and 0.09±0.07 (95% CI ?0.05 to 0.23), respectively.
Conclusions: The result shows that acceptable accuracy in calculations of posterior apical radius and Q was achieved. This new method shows promise for application to the living human cornea.
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KEYWORD
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Anterior corneal topography, Corneal thickness, Posterior corneal apical radii, Posterior corneal asphericity
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