The effect of dot size in random-dot stereograms on the results of stereoacuity measurements

Background This study aimed 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 4 K smartphones. Three dot sizes, including 1 x 1 pixel, 6 x 6 pixels, and 10 x 10 pixels (equivalent to 0.17 min arc, 1 min arc, and 1.68 min arc, respectively), were used to form random-dot arrays, and each test pattern had one Lea symbol 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 (Wilcoxon signed-rank test, Z = -4.903,P < 0.001) and the 10-pixel dots (Z = -4.941,P < 0.001). No significant difference was found between 6-pixel dot and 10-pixel dot stereograms (Z = -1.000,P = 0.317). 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.