Stereoacuity Research Articles

Effect of orthoptic procedures on stereoscopic acuities.

Ten stereophotogrammetry students and three graduate photogrammetrists were given 7 weeks of nonspecific orthoptic exercises. The visual systems of these 13 experimental subjects were matched to those of 13 control subjects chosen from the students and staff of the Ferris State College of Optometry. Stereoscopic acuities were determined before and after the training period on both groups using a Wild Stereoplotter, a Howard-Dolman apparatus, and the Keystone Multi-Stereo Test. Stereoscopic acuities as determined on the stereoplotter and the Howard-Dolman apparatus were improved at better than a 0.05 significance level as computed on the Wilcoxon signed rank test and Student's t-test for the difference between two dependent means.

A Precision Instrument for the Clinical Measurement of Stereoscopic Acuity

When tested by different methods, a patient's stereoscopic acuity is sel­dom the same. This raises the ques­tion as to which one gives the true stereoscopic acuity. To answer this, a programmable test for stereoscopic acuity was designed to serve as a test­ing standard. This is described and a comparative study with it and four other tests is reported.

Stereoscopic Acuity with the New Stereo Test (S. Awaya)

Stereoscopic Acuity with the New Stereo Test (S. Awaya)

Stereoscopic vision with central scotomata (author's transl)

Thirty-nine patients with convergent microstrabismus and 24 patients with central organic scotoma underwent measurements of stereo acuity. Stereopsis at distance was measured by means of a polarization haploscope using "plane-tests" and random dot tests respectively. For near stereopsis were used commercially available tests (Titmus Test, TNO-Test). Organic scotomata can be divided into "circumscribed central scotomata" and "sievelike scotomata", the latter leading to poorer performance in random dot tests. Large plane tests yielded better results than small ones. In microstrabism we found stereo acuities similar to those of patients with "sievelike scotoma". The results support the theory of displacement of fusion within Panum's area in microstrabismus leading to decreased local stereopsis due to decreased concentration of stereo units at the border of Panum's area.

Relationship Between Stereoscopic Acuity and Illumminance

Relationship Between Stereoscopic Acuity and Illumminance

Stereoscopic acuity with defocused and spatially filtered retinal images

Spectacle blur decreases stereoacuity more than ordinary visual acuity, and this cannot be accounted for by contrast reduction or by accommodation and/or convergence instability. Stereoscopic acuity was measured over a range of defocus exceeding 2 D in normal subjects with a 3-mm artificial pupil. Blur of one eye leads to a decrement in stereoacuity that is at least as high and usually higher than blur of both eyes; blurring only the disparate element of the pattern while keeping the rest clear is nearly as detrimental as blurring the whole pattern. In a separate experiment, the individual line elements of the pattern were subjected to spatial frequency filtering in the horizontal direction. For best stereoacuity values, representation of the whole spatial frequency spectrum is required. Patterns with diminished high-frequency content (> 10 cycles/deg) show lowered stereoacuity and those utilizing predominantly a spatial frequency band centered on 22 cycles/deg even more so.

Stereopsis and fixation disparity following prolonged monocular occlusion.

The effects of 12 days of continuous monocular occlusion on the stereoscopic acuity and the magnitude of the fixation disparity associated with a given amount of prism-forced vergence were investigated in six adult subjects with normal binocular vision. After the period of occlusion, all six subjects were able to perceive stereopsis, although four of the six subjects demonstrated a slight but reversible elevation in stereothresholds. The general shape of the fixation disparity curve for a given individual was not altered by occlusion, but changes in the magnitude of the fixation disparity were observed for some subjects.

Cooperative neural processes involved in stereoscopic acuity.

Results of psychophysical experiments are reported showing that synchrony, appropriate relative placement, and absence of standing disparity are important conditions to be met by members of a target configuration if they are to participate in the cooperative neural processes leading to the best disparity discrimination. Consecutive binocular presentation of the members of a stereo target decreases stereoacuity by a factor of about 10, and a step disparity displacement of a single line target needs to be larger still to be detected as a depth stimulus. A standing disaprity of even one minute of arc at least doubles the disaprity disxrimination threshold. It is postulated that a differencing mechanism operates on the depth signal of individual features; the temporal and spatial optima of target presentation for stereoscopic acuity outline the character of the concerned operations.

Stereoscopic Acuity Measurement in Aphakia

We performed a variety of tests to assess binocular function on monocular aphakic patients wearing contact lenses, monocular pseudophakic patients, bilateral spectacle-wearing aphakic patients, bilateral aphakic contact lens wearers, and bilateral pseudophakic patients. Stereoscopic acuity levels at distance and near when visual acuity was at least 6/12 (20/40) provided the most useful data. Pseudophakic patients and contact lens wearers performed equally well and outperformed spectacle wearers. Implant patients did not have superior stereoscopic acuity.

Steroscopic acuity for moving retinal images.

Stereoscopic acuity in the human fovea remains unimpaired with retinal image motions of up to 2 deg/s. These findings apply to lateral motion of the test target alone, and to simultaneous lateral motion of both test and comparison targets. For good steroscopic acuity, depth motion can be tolerated only so long as the configuration does not move outside the disparity zone for optimal stereoscopic acuity, within 2-3 arc min of either side of the fixation plane. The presence during a short exposure of some stimulus components lying outside this zone leads to an overall reduction of stereoscopic acuity, either by dilution through summation, or by active inhibition of the best achievable depth resolution.

Disparity sensitivity and receptive field incongruity of units in the cat striate cortex.

1. Receptive field correspondence and binocular interaction were studied in the cat striate cortex using fundus photography for correction of residual eye drifts. 2. The scatter of incongruities (frequently called receptive field disparities) was found to be equal in horizontal and vertical direction (S.D. 0.5 °, N = 96). Incongruity was not correlated with field orientation. 3. Using binocular stimulation, disparity tuning and binocular facilitation were analysed quantitatively in 46 cells. Seven of these were disparity specific, i.e. showed marked facilitation critically dependent on disparity. 4. With monocular stimulation, three of the seven disparity specific cells could be driven only from one eye; one gave weak responses to both left and right monocular stimulation, and one no monocular responses at all. 5. The disparity specific cells preferred vertical or oblique orientations, and vertical disparity was less critical than horizontal disparity. The disparity tuning curves, plotted with reference to the experimentally determined horopter, showed peaks within 0.5 ° crossed and 0.2 ° uncrossed disparity. The smallest half-widths at half-amplitude were 0.25 °. Some of the curves were asymmetric, or step-like, with a steep slope at zero disparity. 6. It is concluded that stereoscopic depth may be signalled by disparity specific cells in area 17. These cells could account for stereoscopic acuity of a few min arc, if one assumes that depth is encoded in the amount of activity of single units, or in the graded imbalance of activity of antagonistic units. 7. It is argued that the distribution of incongruities does not reflect stereoscopic function because the disparity specific cells often cannot be plotted in both eyes, and most of the units that can be plotted are not disparity selective.

Interference with stereoscopic acuity: Spatial, temporal, and disparity tuning

Stereoscopic acuity in normal human subjects is conspicuously reduced by the presence of contours contiguous to the test pattern. Flanking contours interfere maximally when they are placed about 2.5′ from a test line. and less when this distance is increased or decreased. The largest interference effect is obtained when the flanks are presented 100 msec after the onset of the test pattern. The interference has a quite narrow depth tuning: to halve the threshold elevation the flanks must be presented only 12″. 17″. and 40″ out of fixation plane for the three subjects, respectively. Because a companion experiment shows no such disparity specificity for interference with vernier acuity, the effects described here must operate in the stereo domain.

Rotation and translation effects on stereoscopic acuity

This study examined the effects of rotation or translation on the detectability of a dotted target plane embedded in a dotted masking cube. Julesz-type stereograms were generated in real time, using a small laboratory computer. Subjects displayed an excellent ability to compensate for x-y projected density variations produced by changes in the angle of rotation of the target plane so that performance was equal at all rotations. This finding indicates that dot density is being processed in a three- rather than a two-dimensional manner. Translation of a frontoparallel plane from the back of the stereoscopically defined cube to its front produced systematic changes in performance. Performance was best at the central fixation distance and decreased as either crossed or uncrossed disparity increased. Thus, it appears that stereo acuity decreases symmetrically with increases in disparity in either direction.

Monocular occlusion impairs stereoscopic acuity, but total visual deprivation does not

Wallach and Karsh (1963) reported that 24 h of monocular occlusion leads to a significant deterioration of stereoscopic depth estimates and attributed this phenomenon to “disuse.” We designed an apparatus for testing stereoscopic accuracy which eliminated all cues to depth save binocular disparity. With it, we tested the relative effect of 8 h of monocular—;as opposed to binocular—;occlusion on subsequent stereoscopic performance. Monocular patching led to significant increases in mean standard deviation and in mean absolute error as compared to baseline testing. Binocular patching led to no such impairment. Thus, truedisuse (such as occurs during binocular deprivation) did not impair stereopsis, whereas monocular occlusion, which may involve temporarymisuse of the stereoscopic system, did.

Effects of knowledge of results on dynamic stereo acuity in males and females.

One static and two speed stereo-acuity thresholds were obtained from 8 males and 8 females in both knowledge of results and no-knowledge conditions. There were progressively larger average displacement errors for both males and females as speed of rotation increased. At all speeds, males showed fewer discrimination errors in the knowledge than in no-knowledge conditions. Females showed no consistent differences between these two conditions.

Variation of stereoscopic acuity with observation distance and eye movement characteristics

It has puzzled research workers in perception that stereoscopic acuity decreases with decreasing observation distance, or, equivalently, increasing angle of convergence. Experimental results presented in this paper, as well as evidence published previously, show that the reduction in acuity might be due to rotation of the eyes around their visual axes during convergence which would introduce a disparity for the test lines. Stereoscopic acuity is known to be worse for disparate images. It was proved experimentally that cyclodisparity did lead to a decrease of stereoscopic acuity, supporting this explanation.

Stereoscopic acuity for photometrically matched background wavelengths at scotopic and photopic levels

Two Ss made equidistance settings in a two-rod apparatus using white and four chromatic (red, yellow, Feen, and blue) backgrounds, photometrically matched at each of eight or nine teat levels within a total retinal-illuminance range of 4 log units. The binocular depth setting were analyzed in terms of the angular magnitude of both the Yariable error, ηAD, and the constant error, ηΔR When ηAD is plotted as a function of retinal illuminance, the curves for each of the four chromatic IIIId white backlfound coditions show that at low retinal illuminances, ηAD, is initially large, and with increasing background illumination, ηAD progressively decreases to approach a final low asymptotic value. As predicted by the duplicity theory of vision, each experimental curve shows a dircontinulty at about −1.0 lot td (corresponding to a background luminance value of about 0.0069 fL with the 2.5-mm artificial pupil used) reflecting the transition from rod to cone functioning. The curves representing the different wavelengths essentially overlap throughout the total illumination range, indicating that, for both rod and cone vision, wavelength has no differential effect on the variability of depth settings. The data for ηΔR are less regular than those for ηAD and the rod-cone discontinuities appear less pronounced. The data are analyzed in terms of the relative contribution of the rod and cone mechanisms to performance level.

Stereoscopic Acuity and Retinal Eccentricity

Stereoacuity was measured at various angles from the fovea along horizontal, oblique and vertical meridians. The acuity falls with eccentricity in a nonlinear fashion, and there is a significantly hig

Visual acuity with brief stimuli.

AbstractVernier acuity, stereoscopic acuity and resolving power (“resolution”) have been determined for eight different exposure times, ranging from 4 sec to 0.025 sec, at two levels of luminance with a technique which permits examination under identical conditions for the three visual functions. The results of this study can be summarized as follows. If the exposure time is longer than 0.8 sec, a four‐fold decrease of the luminance of the retinal image influences the three kinds of acuity differently. Vernier and stereoscopic acuities seem to be independent of a reduction of luminance within this restricted range, contrary to the resolution thresholds, which are significantly increased. For exposure times shorter than 0.8 sec, however, also vernier and stereoscopic thresholds are increased by a reduction of the luminance level. For resolution there is a reciprocal relationship between intensity and time according to the formula I × t = Constant, when the exposure time is 0.8 sec or shorter. This relation between intensity and time could not be shown for vernier and stereoscopic acuities. Decreasing exposure time influences stereoscopic acuity more than vernier acuity and resolution. There exists a simple, approximately quadratic relationship between vernier and stereoscopic thresholds, which can be expressed by a straight line if the two acuities are plotted against each other in a log‐log scale. The same relationship is found for both levels of luminance. Stereoscopic acuity is deteriorated more than vernier acuity, if a low degree of heterophoria is introduced under conditions of short exposure times. This is in contrast to performances with long exposure times, where neither of the acuities were influenced by an induced heterophoria.

Automatic determination of the resolving power of the eye.

AbstractA luminous test object, randomly presented either as two parallel lines or as a rectangular band, has been used as the stimulus pattern for an automatic determination of the resolving power of the eye.The effect of blurring of the test object on the resolving power has been investigated in a group of six experimentees.The relation between resolving power, vernier acuity, and stereoscopic acuity, determined under the same conditions, are discussed with special reference to the retinal light distribution.