The Effect of Pupil Dilation on Preoperative Optical Biometry Results for Phacoemulsification: A Meta-analysis

To summarize the effects of pupil dilation on optical biometry results and evaluate its impact on intraocular lens (IOL) power calculations.

A systematic literature search was conducted in PubMed, EMBASE, and Cochrane Library on December 5, 2024. Original studies published from 2010 onward that measured ocular parameters before and after dilation were included. The primary outcome was the change in ocular parameters after dilation; secondary outcomes included the impact of dilation on predicted and postoperative refractive outcomes based on various IOL formulas.

Pupil dilation significantly increased anterior chamber depth (ACD) by 0.08 mm (P < .001), reduced lens thickness (LT) by 0.02 mm (P < .001), and increased white-to-white distance (WTW) by 0.12 mm (P < .001). When compared to using tropicamide, cyclopentolate resulted in a greater increase in ACD (0.03 mm, P = .03) and greater reduction in LT (0.04 mm, P = .001), whereas phenylephrine resulted in less increase in ACD by 0.06 mm (P = .001). There was no significant change in predicted IOL power for third generation formulas, but dilation resulted in a significant increase for the Barrett Universal II and Haigis formulas (both by 0.05 diopters, P = .02 and P < .001, respectively).

Pupil dilation significantly increases ACD and reduces LT, which in turn significantly increases IOL power recommendations by later generation IOL calculation formulas. It would be prudent to consider performing biometry without dilation to avoid its impact on IOL calculation and subsequently final refractive outcome.