Improving interpupillary distance accuracy in the plusoptix A12R: A distance-dependent correction.

Area of Science:

• Ophthalmology
• Optometry
• Biomedical Engineering

Background:

• Handheld photorefractors are widely used for paediatric vision screening.
• Limited patient cooperation and examination time in children necessitate accurate and efficient measurement tools.
• Understanding sources of measurement error in devices like the Plusoptix A12R is crucial for clinical reliability.

Purpose of the Study:

• To investigate the relationship between interpupillary distance (IPD) measurements and measurement distance (MD) using the Plusoptix A12R handheld photorefractor.
• To characterize potential measurement errors in paediatric populations.
• To develop and validate a method to improve the accuracy of IPD measurements.

Main Methods:

• Observed variability in IPD measurements during a paediatric vision screening (n=67).
• Developed a theoretical model predicting a linear IPD-MD relationship with a correction factor.
• Validated the model using bench testing (n=3) and a pilot clinical study (n=8), comparing Plusoptix measurements with a pupilometer using Bland-Altman analysis.

Main Results:

• Significant variability in IPD measurements was noted in children, with 9% showing fluctuations over 4 mm.
• Bench testing confirmed a strong linear dependence of IPD on MD (slope=0.99), with shorter distances yielding larger IPD values.
• The correction factor successfully reduced IPD variability and improved agreement with pupilometer measurements in the pilot study.

Conclusions:

• Measurement distance significantly affects Plusoptix A12R interpupillary distance measurements, introducing systematic error.
• A proposed correction factor effectively compensates for this distance-dependent error.
• Applying the correction factor enhances the clinical reliability of handheld photorefractors for paediatric IPD assessment.