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Introduction: Preoperative cataract assessment may involve multiple biometric instruments and it is important that clinicians are aware of the accuracy, limitations, and interchangeability of keratometry measurements conducted on these instruments.

Purpose: The purpose of the current study was to determine the agreement of keratometry magnitude and axis measurements obtained using three commonly used clinical keratometers.

Design of the study: Prospective, comparative study.

Materials and methods: One-hundred eyes of 100 prospectively enrolled patients listed for cataract phacoemulsification were recruited. Preoperative keratometry magnitude and axis measurements were obtained using the Galilei-G2 Dual Scheimpflug Analyzer (Ziemer Ophthalmic Systems AG, Port, Switzerland), IOLMaster 500, and Takagi ARKM-200 autokeratometer (Takagi Seiko Co., Ltd, Nagano-ken, Japan). Inter-device agreement in corneal spherical equivalent, corneal cylinder vectors, and corneal cylinder magnitude was assessed using the Bland-Altman method.

Results: One participant was excluded because of incomplete data. The Galilei-G2 reported the lowest mean keratometry (43.96 ± 1.71 D) and the IOLMaster reported the highest (43.99 ± 1.65 D). A single statistically significant difference occurred in the corneal cylinder vector analysis between the IOLMaster 500 and the three-instrument pooled mean (mean difference = -0.238 D, P = 0.04). No other statistically significant differences were observed for any instrument for any measured parameter. Excluding the vector difference analysis (range = -0.175 – -0.238 D), mean differences between individual instruments and the three-instrument pooled mean did not exceed 0.025 D (P > 0.05).

Conclusion: The Galilei-G2, IOLMaster 500 (Carl Zeiss Meditec AG, Oberkochen, Germany), and Takagi ARKM-200 autokeratometer produce accurate keratometry and axis measurements that are comparable between instruments. The instruments could be used interchangeably in clinical practice in scenarios where accurate examinations cannot be obtained using one of the instruments.