Can Autorefractometer and Digital Pupillometer Readings of Interpupillary Distance Be Used Interchangeably?: A Cross-Sectional Study

Accurate measurement of interpupillary distance (IPD) is critical for spectacle prescription and binocular vision assessment. This cross-sectional study evaluated the agreement between IPD measurements obtained using an autorefractometer and a handheld digital pupillometer. A total of 88 participants (aged 8–64 years, including 14 aged <18 years) underwent IPD assessment with both instruments under standardized conditions. Agreement was assessed using Bland–Altman analysis with 95% confidence intervals (CIs) for the limits of agreement (LOA), the intraclass correlation coefficient (ICC) for absolute agreement, and a clinical tolerance of ±2.5 mm based on ANSI Z80.1-2020. The mean difference between devices was small and not statistically significant (0.27 mm; 95% CI −0.09 to 0.64 mm; p = 0.14), and the ICC was 0.84 (95% CI 0.77–0.89). However, the 95% LOA were wide (−3.10 to +3.64 mm) and exceeded the clinical tolerance, and 12.5% of participants had between-device differences greater than 2.5 mm. The differences were not associated with age or sex. Although both devices agree well on average, they should not be considered interchangeable for individual patients, particularly where high-precision fitting is required, such as for multifocal lenses and virtual reality systems. Consistent use of the same device across patient encounters is recommended.