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A Quantitative Evaluation of the PowerRef 3 for Measuring Gaze Position.
Jennifer X Haensel1, Kristin E Slinger2, Tyler J Vandiver2
1Spencer Center for Vision Research, Byers Eye Institute at Stanford University, Palo Alto, California, USA. jhaensel@stanford.edu.
Summary
The PowerRef 3 photorefractor accurately measures gaze position within ±8° horizontally and -4° to +10° vertically. Beyond these limits, gaze and refractive measurements may be impacted.
Area of Science:
- Ophthalmology
- Optometry
- Vision Science
Background:
- Accurate gaze position measurement is crucial for reliable refractive error assessment.
- Photorefractors are widely used for non-invasive refractive measurements.
- Understanding the performance limits of photorefractors is essential for clinical application.
Purpose of the Study:
- To evaluate the gaze position measurement quality of the PowerRef 3 photorefractor.
- To assess how gaze position affects refractive measurements obtained with the PowerRef 3.
Main Methods:
- Gaze position was recorded using the PowerRef 3 (50 Hz) in 20 adults at 39 fixation locations.
- Spatial accuracy, precision (RMS-mean, RMS-S2S), and data loss were assessed.
- EyeLink 1000 (500 Hz) was used for reference gaze metrics.
Main Results:
- PowerRef 3 showed spatial accuracy of 1.45° (h) and 1.29° (v) with variable precision.
- Data loss occurred primarily at eccentric horizontal (±20°-±24°) and downward gaze positions.
- Refractive measurements showed hyperopic shifts beyond +10° horizontally and downward, and myopic shifts leftward.
Conclusions:
- The PowerRef 3 reliably records gaze within ±8° horizontally and -4° to +10° vertically.
- Gaze positions outside these ranges may impact both gaze tracking and refractive measurements.
- Clinical use should consider these limitations for optimal accuracy.
