Influence Of The Axial Length–To–Corneal Radius Ratio On Iol Power Calculation Accuracy: A Comparative Analysis Of Nine Formulas
Published 2026 - 44th Congress of the ESCRS
Reference: POCAT590 | Type: Free paper | DOI: 10.82333/mwr6-xn04
Authors: Dr Joao Pedro Antunes* 1 , Dr Miguel Lopes 1 , Dr Nuno Rodrigues Alves 1 , Dr Pedro Gil 1 , Dr Vítor Maduro 1 , Dr Nuno Alves 1 , Dr João Feijão 1 , Dr Diogo Hipólito-Fernandes 1
1Ophthalmology,ULS São José,Lisbon,Portugal
Purpose
To characterize the distribution of the AL/CR ratio in cataract patients and to assess the performance of different IOL power calculation formulas according to AL and AL/CR subgroups.
Setting
Ophthalmology department, ULS São José Lisbon
Methods
Retrospective observational study included 804 eyes who underwent phacoemulsification with in-the-bag implantation of a single-model monofocal IOL. Using optimized lens constants, refractive prediction errors (PE) were calculated for the following formulas: Barrett Universal II, EVO, SRK/T, Holladay 1, Hoffer Q, Haigis, Hill-RBF v2.0, Kane, and PEARL-DGS. Subgroup analyses were performed according to AL/CR ratio (≤2.98, 2.98–3.11, >3.11) and axial length categories (AL ≤22 mm; 22 < AL < 26 mm; AL ≥26 mm). Primary outcome measures included: mean prediction error (ME), standard deviation (SD) of ME, mean absolute error (MAE), median absolute error (MedAE), and percentage of eyes within ±0.25 D, ±0.50 D, and ±1.00 D.
Results
The mean AL/CR ratio was 3.07 ± 0.16. After lens constant optimization, mean prediction error was near zero for all formulas, indicating no systematic bias. The Kane formula achieved the lowest absolute errors and the highest percentage of eyes within ±0.50 D, whereas SRK/T and Hoffer Q showed higher errors. A significant negative correlation was found between postoperative spherical equivalent and axial length, and between spherical equivalent and AL/CR ratio (p < 0.05), but not with corneal radius alone. Subgroup analysis showed reduced accuracy of SRK/T in medium AL with high AL/CR, and of Holladay 1 and Hoffer Q in long AL with high AL/CR, while Kane remained consistent across subgroups.
Conclusions
The AL/CR ratio appears to influence the accuracy of IOL power calculations and may partly explain residual refractive error across different biometric profiles. While the Kane formula demonstrated consistent performance, SRK/T, Holladay 1, and Hoffer Q showed reduced reliability in specific AL and AL/CR subgroups. Consideration of the AL/CR ratio may enhance the understanding of formula behavior and contribute to more individualized IOL power selection.