Analysis of intraocular lens power calculation

We performed an analysis of ocular biometry and intraocular lens (IOL) power calculation on 100 eyes that had anterior chamber IOL implantation during 1981 and 1982. Various methods of calculating the IOL power were used, including the standard lens power, presurgical basic refraction, Fyodorov's formula, Colenbrander's formula, Binkhorst's formula, and the SRK formula. In addition, we took the median value of these calculated results as the median power in selecting an appropriate IOL power. The postoperative refraction and actually implanted IOL power were used to determine the IOL power needed for emmetropia. Our regression analysis of the predicted IOL power and power actually needed for emmetropia showed that the methods of standard power and presurgical basic refraction were unreliable while the rest were of satisfactory accuracy. Among the latter, all the predicted IOL powers based on the biometric data had almost the same coefficient of determination and standard error of estimate. However, with the SRK formula and the median power the values of the regression line were closest to the ideal value. With the regression analysis, the accuracy of predicted IOL power from theoretical formulas was comparable to that of the SRK regression formula.