Effect Of Pupil Size On Biometry Measurements And Intraocular Lens Power In Hyperopic And Myopic Eyes

The purpose of this research was to evaluate the effects of pupil dilation on ocular parameter measurements and intraocular lens (IOL) power calculation using IOLMaster 700 in myopic and hyperopic patients.

This study was conducted at University Department of Ophthalmology, University Hospital Center "Sestre milosrdnice“ Zagreb, Croatia, in the period from December 2022 to March 2023.

A total of 400 eyes were included in this prospective study. Axial length (AL), central corneal thickness (CCT), anterior chamber depth (ACD), lens thickness (LT), flat keratometry (K), steep K, astigmatism, white-to-white (WTW), and pupil width were measured, before and after administration of topical tropicamide. The corresponding IOL powers were calculated using Sanders–Retzlaff–Kraff/theoretical (SRK/T), Haigis, Hoffer Q and Barrett Universal II formulas.

Variations in AL, K1 and K2 following dilation were not significant. The results showed that ACD increased significantly after dilation in both hyperopic and myopic patients whereas LT decreased significantly after dilation. Post-dilation WtW increased significantly as well. When IOL power was calculated as a discrete variable, significant differences were observed between pre- and post-dilation IOL power.

Pupil dilation in myopic and farsighted eyes does not cause significant changes in AL and K. However, it significantly increases the ACD as well as the WtW values ​​and significantly decreases the LT value. Surgeons must estimate pupil width when working with third-generation IOL power calculation formulas (SRK/T, Haigis, Hoffer Q) considering extreme cases. The Barrett Universal II formula had the best match between different pupil conditions in myopic and hyperopic eyes.