Estimation of Corneal Spherical Aberration from Topography

ABSTRACT

PURPOSE: To formulate an equation to estimate corneal spherical aberration using Orbscan (Bausch & Lomb Surgical, Rochester, NY, USA) parameters. METHODS: The study was carried out retrospectively. The participants were 76 eyes of 76 senile cataract patients with the mean age of 57.37 +/- 17.63 years. Both Orbscan and KR-1W (Topcon Corp, Tokyo, Japan) were taken as preoperative examinations. Correlation analysis between various parameters from Orbscan and corneal spherical aberrations for a 6 mm pupil by KR-1W was performed. And multivariable linear regression was performed with the significantly correlated Orbscan parameters from the correlation analysis. RESULTS: The mean corneal spherical aberration from KR-1W system was 0.25 +/- 0.08 microm. As a result of the multivariable linear regression, we could generate following equations. If the Q-value was available, estimated corneal spherical aberration = 0.389 x Q-value + (0.022 x Axial power 3 mm) - 0.633 (R2 = 0.436). If the Q-value was not available, estimated corneal spherical aberration = 0.184 x (Mean power 5 mm - Mean power 3 mm) + (0.02 x Axial power 3 mm) - 0.563 (R2 = 0.429). By using the equations, 93.4-94.7% of subjects were in the error range of 0.10 microm. CONCLUSIONS: Even when equipped with Orbscan only, an appropriate aspheric intraocular lens can be selected using the estimated corneal apherical aberration by the equations.