# Interdevice Agreement of Keratometry, Astigmatism Vectors, and Ocular Biometry in Cataract Candidates: SS-OCT (Argos) vs. OLCI (Aladdin) vs. Scheimpflug–Placido (Sirius)

## TL;DR

This study compares three eye-measuring devices for accuracy in cataract surgery planning, finding significant differences in some measurements.

## Contribution

The study provides empirical evidence on the interchangeability of keratometric and biometric measurements across three optical devices used in cataract surgery.

## Key findings

- Significant inter-device differences were found in K1, K2, and cylinder measurements.
- Vector astigmatism components (J0 and J45) showed no significant differences across devices.
- Argos reported higher anterior chamber depth and white-to-white distance than Aladdin.

## Abstract

Background and Objectives: Accurate anterior segment measurements are central to intraocular lens (IOL) power calculation and toric planning, yet different optical platforms may yield non-interchangeable values. This study compared keratometry, astigmatism metrics, and ocular biometry obtained with a swept-source OCT biometer (Argos), an optical low-coherence interferometry biometer (Aladdin), and a combined Scheimpflug–Placido topographer (Schwind Sirius). Methods: This is a retrospective observational study (January 2022–June 2024) including eyes undergoing uncomplicated cataract surgery. All eyes were measured in a single session by one examiner. Outcomes included K1, K2, cylinder, astigmatism axis (degrees; device-reported corneal cylinder axis, labeled “Powerful Angle” in the Sirius export), vector components (J0 and J45), and—where available—lens thickness (LT), axial length (AL), anterior chamber depth (ACD), white-to-white (WTW) distance, and central corneal thickness (CCT). Friedman tests assessed 3-device differences, and pairwise comparisons were evaluated using Wilcoxon signed-rank tests (paired data). Results: A total of 170 eyes (102 patients) were analyzed (mean age: 69.12 ± 10.26 years). Significant inter-device differences were detected for K1 (Argos: 43.45 ± 1.64 D; Aladdin: 43.41 ± 1.70 D; overall: p < 0.001; Argos vs. Aladdin: p = 0.019), K2 (Argos: 44.45 ± 1.67 D; Aladdin: 44.34 ± 1.71 D; overall and pairwise: p < 0.001), and cylinder (Argos: −0.83 ± 0.74 D, Aladdin: −0.77 ± 0.76 D; Sirius: −0.68 ± 0.75 D; overall: p < 0.001). “Powerful Angle” differed across devices (p = 0.003) but not between Argos and Aladdin (p = 0.512). J0 (p = 0.277) and J45 (p = 0.084) did not differ significantly. Argos reported higher ACD (3.19 ± 0.42 vs. 3.13 ± 0.41 mm, p < 0.001) and WTW (11.95 ± 0.42 vs. 11.65 ± 0.39 mm, p < 0.001) values than Aladdin. CCT was similar between Aladdin and Sirius (540.27 ± 33.44 vs. 540.47 ± 33.78 µm, p = 0.169). Conclusions: Several keratometric and biometric parameters differed significantly by device, indicating limited interchangeability—particularly relevant for toric and premium IOL planning—while vector astigmatism components and CCT showed better agreement.