Impact of pupil dilation on IOL power calculation based on biometric measurements with Heidelberg Anterion

To evaluate the impact of pharmacologic pupil dilation (PD) on biometric measurements and intraocular lens (IOL) power calculation using different generation formulas in patients undergoing cataract surgery.

This prospective study included 126 eyes from 75 patients. Biometric data were obtained before and after pharmacologic dilation using the Anterion Swept-Source OCT biometer (Heidelberg Engineering). Parameters recorded included axial length (AL), mean keratometry (Km), anterior chamber depth (ACD), lens thickness (LT), and white-to-white (WTW) distance. IOL power was calculated using six formulas: SRK/T, Haigis, Barrett Universal II (BUII), Kane, Hoffer QST, and Okulix. Statistical comparisons of biometric values and predicted IOL power before and after dilation were conducted using mixed-effects models.

No significant changes were observed in AL, CCT, LT or Km after dilation. However, ACD, WTW distance and PD showed statistically significant increases (both p < 0.01). IOL power estimations based on SRK/T, Haigis, Hoffer QST, BUII and Kane were not significantly affected after dilation. In contrast, Okulix formulas demonstrated statistically significant variations in calculated IOL power post-dilation (p < 0.0001).

Pharmacologic pupil dilation induces changes in ACD and WTW measurements obtained using the Anterion Swept-Source biometer, thereby influencing IOL power estimation in formulas incorporating these parameters. Ray-tracing Okulix formula is more sensitive to dilation, whereas third-generation formulas remain more stable. Consistency in pupil status during biometry acquisition is essential to ensure refractive predictability.