Effect of cataract-induced refractive change on intraocular lens power formula predictions.

Cataract-induced refractive change (CIRC) is the change in refraction induced by a cataract. It can amount to several diopters (D). It alters predicted errors in refraction following cataract surgery through changes in axial length measurement. This study determined the effect of CIRC on the accuracy of intraocular lens power formula predictions of refraction in 872 eyes of 662 patients. Regression of results gave -0.030 D prediction error per 1 D of CIRC, i.e. cataract-induced myopia and hyperopia tended to yield postoperative hyperopia and myopia, respectively. Theoretical determinations with a model eye supported this result. There was significant correlation of nuclear cataract opalescence with CIRC. Although these effects are difficult to identify based on changes in refraction, if biometers were able to identify cataract density and automatically adjust axial length measurement, IOL power predictions might improve.