PURPOSE: To investigate how the refractive outcomes of pairs of eyes are related. Previous evidence suggests altering intraocular lens (IOL) power for the second eye based on the refractive outcomes of the first eye following cataract surgery, which may not be the correct approach to improve second-eye outcome. METHODS: Retrospective chart review of patients who underwent bilateral cataract surgery during the preceding 12 months was performed, from which 81 patients were recruited. The difference between postoperative refractive error and preoperative target refraction for both eyes was established. The relationship between pairs of eyes was analyzed. RESULTS: The difference from target refraction and post-operative refractive error was statistically significantly correlated between pairs of eyes (t=3.02; P=.003); however, only 10% of the variability in the difference from target refraction for the second eye could be accounted for by the first eye. Even if only the direction of this difference was considered (more myopic or hypermetropic than target refraction), there was concordance between pairs of eyes 63% of the time. This relationship was not modified by age, sex, keratometry, biometry (anterior chamber depth or axial length), or IOL type. CONCLUSIONS: The data suggest that each eye of an individual patient be considered independently when selecting IOL power as part of cataract surgery.