Distribution of corneal spherical aberration in a comprehensive ophthalmology practice and whether keratometry can predict aberration values

PURPOSE: To determine the spherical aberration of the cornea in the general population and whether keratometry readings are predictive of corneal spherical aberration values. SETTING: Private comprehensive ophthalmology practice. METHODS: Corneal spherical aberration and keratometry readings were measured in 696 normal eyes of patients presenting for ocular examination to a comprehensive ophthalmologist. The Easygraph (Oculus) was used to measure the corneal topography and keratometry readings in patients with healthy corneas. The analysis was performed using software in the Easygraph to determine the Zernike coefficients for each cornea. The keratometry and spherical aberration (Zernike coefficient Z(4)(0)) were then statistically analyzed. RESULTS: The corneal spherical aberration, analyzed by the Kolmogorov-Smirnov test for normality, fit a normal Gaussian distribution. The spherical aberration value was (+0.274 +/- 0.089) x 10(-3), measured at an optical zone of 6.0 mm. A very weak correlation was found between corneal spherical aberration and central keratometry readings of the cornea: Corneal spherical aberration = {0.017 x (mean keratometry) - 0.457} x 10(-3). CONCLUSIONS: The corneal spherical aberration distribution was a normal Gaussian curve. However, the mean value was significantly different when the sex of the patient was considered. Corneal keratometry readings could not be reliably used to predict corneal spherical aberration.