Clear and Single Binocular Vision in Near 3D Displays

Abstract

Significance: Accommodation/convergence mismatch induced by 3D displays can cause discomfort symptoms such as those induced by accommodation/convergence mismatch in clinical vergence testing. We found that the limits of clear and single vision during vergence tests are very different between 3D and clinical tests. Clinical vergences should not be used as substitutes for measures of vergences in 3D displays.

Purpose: The purposes of this study were to determine whether the limits of clear and single binocular vision derived from phoropter prism vergence tests match the limits measured in a 3D display and to determine whether vergence mode, smooth versus jump, affected those limits in the 3D display.

Methods: We tested the phoropter prism vergence limits of clear and single vision at 40 cm in 47 binocular young adults. In separate sessions, we tested, in a 3D display, the analogous 40-cm vergence limits for smooth vergence and jump vergence. The 3D fixation target was a Maltese cross whose visual angle changed congruently with target disparity.

Results: Our mean phoropter vergence blur and break values were similar to those reported in previous studies. The mean smooth divergence limit was less in the 3D display (9.8Δ) than in the phoropter (12.8Δ). Most smooth convergence limits were much larger in the 3D display than in the phoropter, reaching the 35Δ limit of the 3D display without blur or diplopia in 24 subjects. Mean jump vergence limits were significantly smaller than smooth vergence limits in the 3D display.

Conclusions: The limits of clear and single binocular vision derived from phoropter vergence tests were not a good approximation of the analogous limits in our 3D display.

Figure 1.

A schematic of the mirror stereoscope apparatus. The left and right image displays are positioned 40cm from the eyes and viewed through mirrors angled to stimulate 15 prism diopters of convergence when viewing the center of each display. The head was supported by a chin/forehead rest (not shown). A vertical touch surface oriented in the sagittal plane of the head allows for manual entry of blur (single tap) and diplopia (double tap) responses.

Figure 2.

This screen shot of the right eye imaging screen shows the Maltese cross fixation target, the far background building image, and the near surrounding leaves when the cross was at a 40cm distance. The cross’ angular size changed with its binocular disparity. The subject was instructed to fixate the center of the cross during trials.

Figure 3.

3D smooth vergences are plotted as a function of clinical smooth vergences for 47 subjects. The 3D divergences are relatively smaller than clinical divergences, but relatively larger in convergence, and smooth 3D divergences were significantly correlated with smooth clinical divergences (broken line through 3D divergence data points and equation). Some individual data points are not visible because of overlap. The number of values for a point are indicated in parentheses, if more than one. Negative values are divergence. Out-of-range 3D display convergence values are plotted at 36 prism diopters. The diagonal line represents equal 3D and clinical values.

Figure 4.

This Bland-Altman plot shows the differences between smooth clinical divergences and smooth 3D divergences as a function of the average of smooth clinical and 3D divergences. The differences between divergences increase with average divergence. “MD” = the mean of the differences = 2.73∆. The broken lines indicate the upper and lower coefficients of agreement (COA).

Figure 5.

The standard deviations (SD) of three repeated 3D divergences are plotted as a function of the mean of those repeats for each subject. The standard deviations increase with mean divergence up to 10∆, and then decrease thereafter. The curved line and its associated equation are a second order polynomial fit to the data points.

Figure 6.

The standard deviations (SD) of three repeated 3D convergences are plotted as a function of the mean of those repeats for those 23 subjects whose responses stayed within the range of the stereoscope. The standard deviations are much larger than in divergence and increase with mean convergence up to 23∆, and then decrease thereafter. The curved line and its associated equation are a second order polynomial fit to the data points.

Figure 7.

3D smooth vergences are plotted as a function of 3D jump vergences for 47 subjects. Smooth vergences are significantly greater than jump vergences, and are not significantly correlated with jump vergences. Some individual data points are not visible because of overlap. The number of values for a point are indicated in parentheses for more than one value. Negative values are divergence. Out-of-range smooth convergence values are plotted at 36 prism diopters, out-of-range jump convergence values are plotted at 20 prism diopters, and out-of-range jump divergence values are plotted at −12 prism diopters. The diagonal line represents equal smooth and jump values.