Chord mu and chord alpha as postoperative predictors in multifocal intraocular lens implantation.

Purpose: With the aging population, the prevalence of presbyopia and the popularity of multifocal intraocular lenses is also growing worldwide. Unfortunately, in some cases, they are still associated with postoperative visual disturbances. Recent literature started to evaluate angle kappa- and angle alpha-derived metrics of chord mu and chord alpha as possible predictive values for visual outcomes after multifocal intraocular lens implantation but the published results are inconsistent between studies. Thus, this article aims to review the role of chord mu and chord alpha as postoperative predictors after multifocal intraocular lens implantation and lay the foundation for further research.

Methods: Relevant articles were identified using the following keywords: "presbyopia," "multifocal intraocular lens," "angle kappa," "angle alpha," "Chord mu," and "Chord alpha" up to June 2022. An attempt was made to present the majority of publications that addressed the topic.

Conclusions: Chord mu and chord alpha have a predictive role on the outcomes after multifocal intraocular lens implantation but to a different extent. Cataract surgeons should take them into consideration and avoid implanting a multifocal intraocular lens for patients with speculated critical values of chord mu and alpha above 0.5-0.6 mm, depending on the device used for measurement and the multifocal intraocular lens implanted. Currently, chord alpha seems to be a more stable, more widely applicable, and reliable determinant in predicting postoperative outcomes and in patient selection prior to multifocal intraocular lens implantation when compared to chord mu. To draw conclusions on the topic, a controlled study is needed.