Individual A-constant determination in IOL power calculation with the SRK-formula

Abstract

The accuracy of all implant calculations is dependent on the implant manufacturer, implant style, measuring equipment, measuring methods and the surgeon’s technique. Main error sources are to be found in individual biometric methods and surgical techniques. They can only be detected and eliminated by a postoperative refraction control. In most of the cases it is not possible to determine whether a systematic prediction error is caused by a systematic error of biometry, by surgical technique or by both of them. Since the SRK-formula (1) is linear, every constant systematic measurement error is expected to cause a constant systematic deviation from the desired postoperative refraction. On the other hand every kind of systematic postoperative prediction error can simply be corrected in future calculations by a changed A-constant.