Precalculated artificial lens implantation with refractive balance

The two main possibilities of error of the generally used methods for artificial lens implantation after preoperative ultrasound measurements and calculations are discussed. By using our additional special calibration to the ultrasonic equipment we can predict the postoperative refraction with an error of +/- 0.5 D corresponding to an uncorrected vision of about 20/40 and better. Procedures based on the validity of Knapp's law may lead to optical pitfalls, since Knapp's law is only valid for eyes with variable eye length, while it is known that human phakic, pseudophakic and aphakic eyes have a constant eye length. Three principles for the precalculated artificial lens implantation are published and results of refractive balances are given.