Secondary IOL power calculations: a comparison of regression formula and refraction method in accurate prediction of emmetropia.

A retrospective review of 51 secondary intraocular lens (IOL) implantations was made to determine the relative accuracy of the SRK regression formula and the refraction method described by Holladay in preoperative prediction of emmetropic IOL power. The regression formula accurately predicted emmetropia within 1 diopter (D) in 63% of patients; the refraction method accurately predicted within 1 D in only 26% of cases. The emmetropic power predicted by the two formulas differed by at least 1 D in 76% of patients. Precise measurement of preoperative variables is imperative to ensure accurate prediction of emmetropic IOL power in the patient considered for secondary implantation.