Using the first eye prediction error in cataract surgery to refine the refractive outcome of the second eye: a comparison of two methods in a paired-eye dataset of 605 patients

Session Details

Session Title: IOL Power Calculations, Post-LASIK & Extreme Eyes

Session Date/Time: Tuesday 25/09/2018 | 14:00-16:00

Paper Time: 14:06

Venue: Room A2

First Author: : A.Turnbull UK

Co Author(s): :    G. Barrett                    

Abstract Details

Purpose:

To derive adjustment coefficients for intraocular lens (IOL) power selection based on the prediction error (PE) of the first eye having cataract surgery, in order to refine the refractive outcome for the second eye. To investigate whether the optimum adjustment coefficient differs among commonly used IOL power formulae. To establish whether optimising the IOL constant for an individual patient based on the first eye PE and using this to inform IOL selection in the second eye has advantages over an IOL formula-specific adjustment coefficient.

Setting:

1. University Hospital Southampton, Southampton, UK 2. Sir Charles Gairdner Hospital, Perth, Australia

Methods:

75 patients who underwent bilateral sequential cataract surgery by a single surgeon in Australia were retrospectively analysed. Only eyes with postoperative BCVA ≥6/12 were included. Postoperative subjective refraction was compared with predicted postoperative refraction (PPOR) calculated by the Barrett Universal II (BUII), Haigis, Hoffer Q, Holladay and SRK/T formulae, to determine PE. PPOR adjustment coefficients derived from this dataset were compared with a different paired-eye dataset of 605 UK patients. Additionally, patient-specific IOL adjustment coefficients were derived from optimised IOL constants based on the first eye. Ability of these methods to improve second eye PE was compared.

Results:

Formula-specific adjustment coefficients based on PE ranged from 0.5 to 0.6 for Haigis, Hoffer Q, Holladay and SRK/T, and 0.33 for BUII. After applying these adjustment coefficients, the percentage of patients within 0.5D of predicted postoperative refraction in the second eye improved from 65.9%, 65.3%, 69.1%, 67.8% and 70.7% with Haigis, Hoffer Q, Holladay, SRK/T and BUII respectively, to 69.1%, 68.4%, 71.4%, 72.2% and 73.6%. An optimum adjustment coefficient derived via regression analysis from patient-specific optimised IOL constants improved the error in predicted outcome, but was less effective and more complex than using a formula-specific adjustment coefficient.

Conclusions:

IOL formula-specific adjustment coefficients can improve the percentage of patients achieving the refractive target with their second eye. This method has value across all the investigated formulae, but the improvement is greater with earlier generation formulae in which the prediction of effective lens position is less accurate. Using an individually optimised IOL constant derived from the first eye PE offers an alternative approach, but in this series was slightly less beneficial than using a formula-specific adjustment coefficient. Second eye refinement necessitates waiting one month to achieve refractive stability, before determining the first eye PE and proceeding with the second eye.

Financial Disclosure:

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