Researchers identify measurement distance as source of IPD variability

Interpupillary distance (IPD) measurements from the Plusoptix A12R handheld photorefractor can be affected by how far the device is held from the patient, according to a study, which suggests this may be creating a predictable source of error during pediatric vision screening.

Investigators observed variability in IPD readings during a pediatric vision screening program, prompting further evaluation of how measurement distance (MD) affected results.

To investigate, the team developed a model showing a linear relationship between IPD and MD. Bench testing confirmed that shorter measurement distances led to larger IPD values, with a strong correlation between the 2 factors.

The researchers then tested a correction factor designed to adjust for this error. In a small pilot study of 8 participants, applying the correction reduced IPD variability and improved agreement with standard pupilometer measurements.

The authors concluded that measurement distance introduces a systematic error in Plusoptix A12R IPD readings, but this can be effectively corrected to improve clinical reliability.

Reference
Rendo-González S, Garcia-Porta N, Arines J. Improving interpupillary distance accuracy in the plusoptix A12R: A distance-dependent correction. J Optom. 2026;19(3):100613. doi: 10.1016/j.optom.2026.100613. Epub ahead of print. PMID: 42001780.