Prediction of intraocular lens position after cataract extraction

A formula is presented for calculating the postoperative position of an anterior chamber intraocular lens (IOL) from preoperative data on chamber depth, lens thickness, corneal curvature and diameter. The formula was arrived at by regression analysis of preoperative and postoperative data on 80 patients receiving an anterior chamber lens after intracapsular cataract extraction. The significant predictors, in order of importance, were the height of the cornea, regarded as a section of a sphere (P less than 0.001), the preoperative chamber depth (P less than 0.01), and the preoperative lens thickness (P less than 0.05). The axial length did not show a significant correlation with postoperative chamber depth (P greater than 0.05). Using the regression formula, the postoperative chamber depth could be predicted a posteriori with an accuracy of +/- 0.22 mm (SD) and a correlation coefficient of 0.58. The method described may be applied to other types of IOLs and may increase the accuracy of IOL power calculations.