Relationship between intraocular lens power and ocular refraction variations

Abstract

Purpose: To develop a theoretical method to predict the theoretical ratio between changes in intraocular lens (IOL) power (dP) and induced variations in ocular refraction (dR).

Setting: Rothschild Foundation Hospital, Paris, France.

Design: Theoretical study.

Methods: The theoretical changes in dP required for desired variations in dR and influencing variables were computed using a paraxial pseudophakic eye model. This formulation was subsequently validated against the Haigis formula, using half-diopter power increments for comparison. Various eye models, covering a range of axial lengths, keratometry readings, and effective implant positions, were analyzed. In addition, the impact of keratometry and effective lens position (ELP) on the IOL power-refraction change ratio was evaluated.

Results: The findings highlight the significant roles of keratometric power and ELP in determining the theoretical magnitude of IOL power increment required for a specific dioptric change in refraction. The study extended beyond standard keratometry values to include a wider range of clinical scenarios.

Conclusions: This model provides theoretical trends for guiding clinicians in predicting the necessary IOL power adjustments for desired refractive changes in pseudophakic eyes. This work also suggests potential applications in the fine tuning of adjustable IOLs and more customized IOL power selection for a range of refractive surgeries.