# Effect of pupil dilation on spherical and toric IOL calculations using a swept source OCT ocular biometer

## TL;DR

This study finds that pupil dilation has minimal impact on IOL power calculations for most eyes, though some cases may see clinically relevant changes.

## Contribution

The study evaluates the effect of pupil dilation on spherical and toric IOL calculations using multiple formulas and vector analysis.

## Key findings

- Pupil dilation increased central corneal thickness but did not significantly affect IOL power calculations.
- Most eyes showed minimal changes in IOL power, but some experienced clinically relevant differences.
- Vector analysis showed small differences in corneal astigmatism and toric IOL parameters post-dilation.

## Abstract

We aim to evaluate the effect of pharmacological pupil dilation on spherical and toric intraocular lens (IOL) power calculations using biometric measurements from the Anterion optical biometer.

This was a prospective observational study of adults undergoing cataract surgery. Pre- and post-dilation biometric measurements were obtained using the Anterion biometer. IOL power calculations, including both spherical and toric values, were performed using the following formulas: Barrett Universal II, Cooke K6, EVO, Hill-RBF, Hoffer® QST, Kane, and Pearl-DGS. Vector analysis was used to compare pre- and post-dilation corneal astigmatism and toric IOL magnitude and axis.

A total of 74 eyes from 37 patients (17 male, 20 female; mean age 52.4 ± 7.8 years) were analysed. Pupil dilation resulted in a statistically significant increase in reported central corneal thickness (CCT, p < 0.05), while other biometric parameters remained unaffected. Both spherical and toric IOL power calculations showed no significant changes across formulas following dilation. Vector analysis revealed that the centroid difference in corneal astigmatism and toric IOL magnitude ranged from 0.09 D to 0.05, and axis orientation differences ranged from 3° to 6°, indicating no systematic bias due to dilation.

Approximately 75% of eyes showed changes of < 0.50 D in spherical IOL power, while ~ 25% exceeded 0.50 D. For toric IOL power, ~ 90% of eyes showed changes < 0.50 D, with ~ 25% reaching or exceeding 0.50 D.

Most eyes show minimal IOL power variation with pupil dilation; however, a subset may experience clinically relevant differences, particularly in toric IOL calculations.

The online version contains supplementary material available at 10.1007/s10792-026-03939-6.