Eccentricity, asphericity and shape factor values of the normal cornea

Purpose

To measure the mean corneal eccentricity, asphericity and shape factor values of normal anterior corneal surface using Orbscan IIz device and to evaluate their relationship with central corneal curvature.


Material and methods

There were analyzed 174 corneal topography records of 87 patients for refractive surgery. Eccentricity, asphericity and shape factor values calculation were performed by Orbscan IIz topography system in zones of 6.0 and 8.0 mm diameters.


Results

The mean values of corneal eccentricity, asphericity and shape factor were obtained: 0.24±0.18; —0.09±0.11; 0.91±0.11 for a 6.0 mm measurement zone and 0.51±0.08; —0.26±0.10 and 0.74±0.10 for a 8.0 mm diameter zone respectively.


Conclusion

More homogenous results were obtained in the 8.0 mm measurement zone. There was no correlation between obtained values and corneal curvature.