Using The First Eye Back-Calculated Effective Lens Position To Improve Refractive Outcome Of The Second Eye.

The present study is a retrospective, mono-centric case series that aims to compare second-eye IOL power calculation precision using back-calculated lens position (LP) as a lens position predictor versus using a predetermined correction factor (CF) for thin and thick lens IOL calculation formulas. 

Retrospective data extraction of all patients who benefited from sequential bilateral cataract surgery and implnatation of Finevision IOLs (BVI PhysIOL, Liège, Belgium) from April 2017 to December 2019 by cataract surgeons of our team (15 surgeons in total).

A set of 878 eyes from 439 patients with both operated eyes was used as a training set to create Haigis-LP and PEARL-LP formulas, using the back-calculated lens position of the contralateral eye as an effective lens position (ELP) predictor. Haigis-CF, Barrett-CF, and PEARL-CF formulas using an optimized correction factor based on the prediction error of the first eye were also designed. A different set of 1500 eyes from 1500 patients operated in the same center was used to compare the basal and enhanced formula performances.

IOL power calculation for the second eye were significantly enhanced by adapting the formulas using back-calculated ELP of the first eye or by using a correction factor based on the prediction error of the first eye, the latter giving substantially higher precision. A decrease in a mean absolute error of 0.132 D was observed between the basal PEARL and the PEARL-CF formula (p<0.0001). The optimal correction factor was close to 80% of the first eye prediction error for every formula. 

Fixed correction factor of 80% of the postoperative refractive error improves second eye refractive outcome better than IOL formulas' adjustment by predicting effective lens position. Significant inter-ocular biometric dissimilarity precludes enhancement of the second eye IOL power calculation according to first eye results.