Predicting the Postoperative Addition Power of a Multifocal Intraocular Lens at the Spectacle Plane

PURPOSE: To establish a simple clinical method of predicting addition power achieved with a multifocal intraocular lens (IOL). METHODS: In this prospective cohort study, 41 patients were bilaterally implanted with the Bi-Flex MY multifocal IOL (Medicontur) with +3.50 diopters (D) near addition power. Monocular defocus curves were plotted for each patient and effective addition power was calculated as the dioptric difference between the distance and near inflection points of the defocus curve. Six biometry formulas (Haigis, Holladay, SRK/T, Hill RBF, Barrett Universal II, and Holladay 2) were used to predict the addition power at the spectacle plane. RESULTS: Mean effective addition power was 2.60 +/- 0.29 D, with significant (P < .01) differences between the prediction methods. Significant differences were found between predicted and effective addition when the Holladay, SRK/T, Hill RBF, and Holladay 2 formulas were used. A moderate but significant correlation (r = 0.342, P = .033) was found with the Barrett formula, and this was also the method to show the least proportional bias with Bland-Altman analysis. CONCLUSIONS: The study demonstrates that the effective addition power can be predicted using the proposed simple clinical method derived using the Barrett Universal II formula. The proposed technique may have significant clinical value in screening for patients where ocular biometry may lead to aberrant addition power.

Automated summary

The study established a simple clinical method to predict effective addition power with a multifocal intraocular lens, using the Barrett Universal II formula. There were significant differences between prediction methods, with the Barrett formula showing the least bias.