Background
The aim of this study was to evaluate the effect of the size of the dots in random-dot stereograms on the results of stereoacuity measurements.
Methods
A stereopsis measurement system was created using a phoropter and two 4K smartphones. Three dot sizes, including 1×1 pixel, 6×6 pixels, and 10×10 pixels (equivalent to decimal acuity 6.0, 1.0, and 0.6, respectively), were used to form random-dot arrays, and each test pattern had one digit hidden within it. The resulting stereograms were tested on 30 subjects with normal acuity and stereoacuity.
Results
Stereoacuity measured with the 1-pixel dots was significantly worse than that measured with the 6-pixel dots (Mann-Whitney U test, Z=-6.531, P<0.001) and the 10-pixel dots (Z=-6.494, P<0.001). No significant difference was found between 6-pixel dot and 10-pixel dot stereograms (Z=-0.443, P=0.658).
Conclusion
The size of the dots in random-dot stereograms affects the test results significantly when the dots are too small for the eye to resolve.