Postoperative Biometry and Keratometry after Posterior Chamber Lens Implantation

Abstract

In intraocular lens (IOL) power calculations, the postoperative intraocular distances and corneal curvatures have to be known. Prior to surgery these data are unknown and can only be guessed at from measurements performed preoperatively. Therefore, the relationship between the respective pre- and postoperative data is of utmost importance. For the present study, postoperative biometric and keratometric measurements were performed on 101 eyes at least 6 months after routine cataract extraction and posterior chamber lens (PCL) implantation and were compared to preoperative results. Lens geometry was plano-convex for 96 lenses and convex-concave for five lenses. For corneal curvatures, a linear correlation between pre- and postoperative radii was obtained with a correlation coefficient of 96%. A multiple regression analysis yielded correlation coefficients as high as 70%, if the postoperative ACD (anterior chamber depth) was correlated with the preoperatively measured ACD, the lens thickness and axial length data. The apparent decrease in axial length after surgery was found to be due to a systematic biometric error caused by the IOL, which generally affects pseudophacic ultrasonic measurements. After allowance was made for this effect, no significant difference was found between pre- and postoperative axial lengths.