Improvement of intraocular lens power calculation using empirical data.

A simple lens power calculation formula of the form: Predicted implant power = A + B X axial length + C X keratometry, can be produced with different constants (A, B, and C) for each type of lens implant and each manufacturer. We have determined the constants for iris-fixated, anterior chamber and posterior chamber lens implants, based on data from 923 cases. The results have been more accurate than those from presently available theoretical formulas, and the well-known phenomenon of predicting too much dioptric power in eyes with short axial lengths has been avoided. Only 1% of the cases had a predicted lens power more than 3 diopters in error.