Influence Of Optional Biometric Variables On Refractive Outcomes Predicted Through The Barrett Uii Formula
Published 2023 - 41st Congress of the ESCRS
Reference: PP22.10 | Type: Free paper | DOI: 10.82333/s5ts-sa29
Authors: Telmo Cortinhal* 1 , Pedro Nuno Pereira 1 , Nuno Gouveia 1 , Inês Figueiredo 1 , Miguel Raimundo 2 , Conceição Lobo 2 , Joaquim Murta 2
1Department of Ophthalmology,Centro Hospitalar e Universitário de Coimbra - CHUC,Coimbra,Portugal, 2Department of Ophthalmology,Centro Hospitalar e Universitário de Coimbra - CHUC,Coimbra,Portugal;Faculty of Medicine,University of Coimbra,Coimbra,Portugal;Clinical Academic Center of Coimbra,CACC,Coimbra,Portugal
Purpose
Modern intraocular lens (IOL) calculation formulas depend on a set of mandatory biometric parameters – axial length (AL), keratometry, anterior chamber depth (ACD) – as well as optional biometric parameters. The Barrett Universal II (BUII) formula considers two optional parameters - lens thickness (LT) and white-to-white distance (WTW). Such parameters may not be measurable using older optical biometry devices. Currently there is a lack of evidence regarding their effect on refractive outcomes. We compare refractive outcomes of uncomplicated cataract surgery with and without the use of optional parameters.
Setting
Academic university hospital
Methods
Retrospective consecutive case study of eyes that underwent uncomplicated cataract surgery with single-piece monofocal intraocular lens implantation (Alcon SN60AT). We compared the predicted spherical equivalent (SE) for the implanted lens obtained by the BUII formula, with and without optional parameters, to the postoperative SE obtained by subjective refraction 6-12 weeks post-operatively. The primary outcome variable was the absolute prediction error (AE) evaluated by median (MedAE) and interquartile range (IQR). A multivariate logistic regression model for the odds of improving the predictions was fitted with biometric variables.
Results
We included 1346 eyes with mean AL of 23.36±1.08 mm (20.87-29.73), ACD of 3.32±0.39 mm (2.12-4.36), LT of 4.59±0.42 mm (3.12-6.00) and WTW of 11.85±0.41 mm (10.51-13.36). After optimization, the median AE with optional parameters was significantly lower than without (with optional parameters: MedAE 0.283D, IQR 0.310; without: 0.289, IQR 0.326; p=0.005). The post-operative SE prediction changed by more than 0.1D (absolute values) in 26.15% (n=352). In this subset, a more accurate prediction was seen in 44.9% of cases (n=158), notably with lower LT (LT < 4.17 mm, 1SD cutoff, OR 1.96. p=0.013) and more extreme WTW (WTW > 12.67 or < 11.03, 2SD cutoff, OR 3.00, p=0.015).
Conclusions
In our sample, the inclusion of optional biometric variables in the Barrett UII significantly improved outcomes, changing predictions by more than 0.1D in approximately one-fourth of cases. Improved predictions were mainly seen in eyes with lower-than-average pre-operative LT and more extreme pre-operative WTW (both lower and higher).