BackgroundTo determine the stereoacuity threshold with a 3D laptop equipped with 3D shutter glasses, and to evaluate the effect of different shape and size of test symbols and different type of disparities to stereoacuity.MethodsThirty subjects with a visual acuity in each eye of at least 0 logMAR and a stereoacuity of at least 32 arcsec (as assessed in Fly Stereo Acuity Test) were recruited. Three target symbols—tumbling "E", tumbling "C", and "□"—were displayed, each with six different sizes representing a visual acuity ranging from 0.5 to 0 logMAR when tested at 4.1 m, and with both crossed and uncrossed disparities. Two test systems were designed - fixed distance of 4.1 m and one for variable distance. The former has disparities ranging from 10 to 1000 arcsec. Each subject completed 36 trials to investigate the effect of different symbol sizes and shapes, and disparity types on stereoacuity. In the variable distance system, each subject was tested 12 times for the same purposes, both proximally and distally (the point where the 3D effect just appears and where it just disappears respectively), and the mean value was calculated from the mean proximal and distal distances.ResultsNo significant difference was found among the groups in the fixed distance test system (Kruskal-Wallis test; Chi-square = 29.844, P = 0.715). Similarly, no significant difference was found in the variable distance system (Kruskal-Wallis test; proximal: Chi-square = 5.687, P = 0.338; distal: Chi-square = 5.898, P = 0.316; mean: Chi-square = 6.152, P = 0.292).ConclusionsEvaluating stereoacuity using this measurement system was convenient and effective. Changes in target shape and size and disparity types had no significant effect on stereoacuity. It would be helpful to choose optimal targets according to different purposes using computer-assisted 3D measurements.Electronic supplementary materialThe online version of this article (doi:10.1186/s12886-016-0223-3) contains supplementary material, which is available to authorized users.

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The closely spaced pixels of a 4K smartphone display enable measurement of stereoacuity at a relatively short distance. The flexibility and versatility of the mobile test system are likely to be useful in clinical practice.

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Background: The purpose of having a naked eye 3D glasses-free smartphone is to achieve 3D effects without the need for glasses. The purpose of this study was to evaluate whether this technology could be utilized to measure stereoacuity. Methods: A 2K auto-stereoscopic smartphone was used to imitate the quantitative section of Random Dot Stereo Acuity Test (contour based symbol) and Random Dot 3 Stereo Acuity Test (random dot based symbol) to measure the stereopsis of subjects. Results: There was a high level of agreement between the two methods using Bland-Altman statistical analysis (vs. Random Dot Stereo Acuity Test, 95% limits of agreement ±1.29 arcseconds; vs. Random Dot 3 Stereo Acuity Test, 95% limits of the agreement also ±1.29 arcseconds). Conclusions: The auto-stereoscopic smartphone is a useful tool to evaluate stereopsis.

PurposeTo investigate the influence of induced aniseikonia on stereopsis measured by contour-based and random-dot-based stereograms using a new method.MethodsUnlike previous studies in which aniseikonia was induced using magnifiers, which potentially influenced the position of the test symbols in the half-view, here the image was magnified while maintaining each test symbol’s central position within the half-view. A phoropter and two 4K smartphones were used to measure stereopsis in seventeen young adults aged 20–28 years old. Stereopsis was tested using both contour-based and random-dot-based stereograms under overall or meridional aniseikonia with magnifications ranging from 2.5 to 30%. Repeated measures ANOVA was used to evaluate the effect of aniseikonia on stereopsis.ResultsStereopsis decreased with an increase in aniseikonia magnification in the overall, horizontal, and vertical directions. Stereopsis values (log arcsec) increased from 1.29 ± 0.14 at baseline to 2.38 ± 0.16 with 30% overall aniseikonia of contour-based stereograms. In random-dot based stereograms, stereopsis values increased from 1.29 ± 0.16 at baseline to 2.24 ± 0.23 with 22.5% overall aniseikonia. Overall aniseikonia caused a significantly greater impairment on stereopsis as compared with the changes in meridional directions. In contour-based stereograms, vertical aniseikonia had significantly less impact on stereopsis than horizontal aniseikonia of identical magnification. The opposite phenomenon was found in random-dot-based stereograms.ConclusionStereopsis decreased with an increase of magnification of induced aniseikonia. Magnifying patterns (overall, horizontal, or vertical) also significantly affected stereopsis. The conflicting impact of meridional aniseikonia on stereopsis measured by contour-based and random-dot-based stereograms may be associated with the uniqueness of the two test systems.

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 × 1 pixel, 6 × 6 pixels, and 10 × 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.

Several studies have revealed that results of the TNO stereo test may overestimate the stereoacuity value (the less the better) compared with other testing measurements. The manner in which vision is divided among two eyes of a person wearing anaglyph glasses may play an important role. This study aimed to examine the effect of anaglyph glasses on stereopsis measurements. A stereopsis measurement system using a phoropter and two Sony smartphones was established. Four types of test patterns, including the original TNO stereo test pictures, isoluminant red-green pictures, grayscale pictures, and black and white dots pictures, were designed. A total of 32 participants were recruited for this study. A significant difference was found among the four groups (Friedman test, chi-square = 50.985, P < 0.001 ). The Wilcoxon signed-rank test was used to detect differences between the groups. The stereoacuity of the original TNO group was significantly worse than those of the isoluminant, grayscale, and black-white groups. However, no significant difference was found between the isoluminant and grayscale groups. The correlation coefficient between the original TNO and isoluminant groups was 0.952 (Spearman’s rho, P < 0.001 ; 95% confidence interval (CI), 0.901–0.988), while that between the original and grayscale groups was 0.771 (Spearman’s rho, P < 0.001 ; 95% CI, 0.550–0.916). Anaglyph glasses played an important role in determining the stereoacuity values with the TNO stereo test, and the results were overestimated when compared with that of the other testing methods. The imbalance of chroma and luminance between the two eyes caused by the anaglyph glasses was indicated as one of the reasons for the overestimation of stereo thresholds.