Pupil size differences between female and male patients after cataract surgery

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.

Intra-Observer and Inter-Observer Variability of Intraocular Lens Measurements Using an Interferometry Metrology Device

The NIMO TEMPO (Lambda-X, Nivelles, Belgium) is a novel, user-friendly and compact device designed for in vitro optical analysis of refractive and diffractive intraocular lenses (IOLs). This device analyzes the IOL wavefront and generates a synthetic eye model for numerical computation. The objective of this study was to evaluate the precision of this innovative device. Intra- and inter-observer variability were calculated using a two-way analysis of variance (ANOVA) after conducting ten measurements of eight different IOL models, with each measurement being repeated by three distinct operators (resulting in a total of 30 measurements for each IOL). The device demonstrated satisfactory intra- and inter-observer variability in evaluating IOL power and modulation transfer function (MTF) profiles, with values of 0.066 and 0.078 diopters for IOL power and 0.018 and 0.019 for MTF measurements, respectively. Furthermore, this hybrid optical and numerical in vitro IOL wavefront analyzer appears to have several advantages over conventional optical bench devices. It reduces the need for operator manipulation, and allows for numerical modeling of various optical environments, including cornea models and apertures. In conclusion, this novel metrology device designed for refractive and diffractive IOLs appears to provide a satisfactory precision, making it a promising tool in the field of IOL metrology.

Agreement between Two Devices for Measuring Pupil Diameter in Patients Implanted with Multifocal Intraocular Lenses

The purpose of this study was to evaluate the agreement between three methods for measuring pupil size in patients implanted with multifocal intraocular lenses (MIOLs): Keratograph 5M (K5M), Pentacam AXL Wave (PW), and a simple hand ruler. Sixty-nine subjects implanted with MIOLs and measured at the three-month follow-up visit were included in this retrospective analysis. K5M and PW were used to measure the photopic (PP) and mesopic (MP) pupil sizes, and a hand ruler was used to measure the pupil under environmental light conditions (135 lux). The Bland-Altman method with its limits (LoAs) was used to assess the agreement. The median PP was 2.8, 2.95, and 3 mm for K5M, PW, and the ruler, respectively (p < 0.05). Differences in PP were statistically significant for all paired comparisons (p < 0.0005) except between PW and the ruler (p = 0.44). The LoAs for the difference in PP between K5M and PW was 0.63 mm. The mean difference for MP between K5M and PW was 0.04 mm (p = 0.34) with LoAs of 0.72 mm. MP measured with K5M and PW could be considered interchangeable, although a correction of -0.3 mm (IC95%: -0.23 to -0.39) should be applied to PP measured with PW to attain the K5M mean.