Distance Stereotest Research Articles

A New Distance Stereotest by Autostereoscopic Display Using an Eye-Tracking Method.

Objectives: This research aimed to present a novel glasses-free distance random-dot stereotest system (GFDRDSS) using an eye-tracking method. Methods: A single-view autostereoscopic display applying a backlight control system combined with an eye-tracking method and the corresponding random-dot stereotest software were developed to create a GFDRDSS with a viewing distance of 5 m. The stereoacuity of 12 subjects with normal eye position was evaluated using the Randot Stereotest, Stereoscopic Test Charts vol. 3 (Yan’s Charts), Distance Randot® Stereotest, and GFDRDSS. Results: The GFDRDSS could provide distinct and stable glasses-free stereoscopic perception even while the subject was moving their head. It could evaluate binocular disparities of 40–2,400 arcsec. Eleven subjects with normal near visual acuity had fine near stereovision (20–60 arcsec) using the Randot stereotest and Yan’s Charts. Under refractive correction, 10 subjects had fine stereovision (≤60 arcsec) using the GFDRDSS at a distance of 5 m, and 9 had fine stereovision using the Distance Randot® Stereotest at 3 m. Other subjects described the 100 arcsec-level stereograms correctly. The results exhibited a concordance of stereoacuity within one degrade between the two distance stereotests. Conclusion: The proposed GFDRDSS can alternately project a couple of random-dot stereograms to the subjects’ eyes and provide a glasses-free distance stereotest, which showed good concordance with the Distance Randot® Stereotest. More data are needed for statistical studies.

Correlation between Frisby-Davis Distance Stereoacuity Scores and Long-term Surgical Outcomes in Intermittent Exotropia

Purpose: We analyzed postoperative Frisby-Davis distance (FD2) stereotest scores and changes in the angle of deviation, and the correlation between postoperative FD2 stereotest scores and long-term surgical outcomes, in patients with intermittent exotropia.Methods: This retrospective study included patients aged less than 12 years with intermittent exotropia who underwent at least 28 months of postoperative follow-up. We analyzed the changes in the postoperative angle of deviation and preoperative and postoperative Titmus and FD2 stereotest scores. Surgical success rates at 28 months postoperatively were compared between the good (FD2 at 10 months postoperatively ≤ 10 arcsec) and bad (FD2 at 10 months postoperatively ≥ 15 arcsec) stereotest groups. Surgical success was defined as a horizontal deviation on distance measurement of 5 prism diopter (PD) esodeviation to 10 PD exodeviation at 1 year postoperatively.Results: This study included 101 patients. No significant difference was identified between preoperative and postoperative Titmus test scores. However, the FD2 stereotest scores were significantly improved at 10 months postoperatively (p = 0.001). A significant, positive correlation was observed between FD2 stereotest scores at 10 months postoperatively and the angles of deviation at distance at 10, 16, 22, and 28 months postoperatively (p ≤ 0.001 for all). The surgical success rates at 28 months postoperatively were 73.1% and 43.5% in the good and bad stereotest groups, respectively (p = 0.008).Conclusions: Distance stereoacuity within 1 year postoperatively correlated with the postoperative angle of deviation at distance. Good distance stereoacuity (i.e., < 10 arcsec) within 1 year postoperatively correlated with a higher surgical success rate compared to bad distance stereoacuity.

Validity and repeatability of contour-based visotec distance stereoacuity test

ABSTRACTClinical RelevanceThe clinical assessment of distance stereoacuity is important in some ocular conditions. Given the different neurophysiological mechanism for crossed and uncrossed stereoacuities, evaluation of both may provide additional insight into binocular vision disorders.BackgroundClinical devices measuring distance crossed and uncrossed stereopsis are not readily available. Visotec Distance Stereo Test (VDST) is a contour-based device designed to measure both forms of distance stereoacuity. This study assesses the validity and test–retest reliability of the device in comparison to the random dot-based Randot Distance Stereo Test (RDST).MethodVDST and RDST were administered to a total of 107 children, that included 51 ‘normal’ and 56 ‘abnormal’ (37 intermittent exotropia and 19 amblyopia) between the ages of 5 and 15 years. Two examiners retested stereoacuities in a sub-set of 62 randomly selected subjects. Stereoacuity was transformed to log scale. 95% limits of agreement were calculated for test–retest reliability. The Bland–Altman plot was used to demonstrate the agreement between the tests and the examiners.ResultsThe mean ± SD crossed distance stereoacuities using VDST in normal, intermittent exotropia and amblyopic children were 93.1 ± 43.8, 161.9 ± 89.8 and 236.3 ± 122.4 arcseconds, respectively. For uncrossed stereoacuity, these were 104.7 ± 54.0, 187.6 ± 89.6 and 265.5 ± 144.0 arcseconds, respectively. Crossed stereoacuity was significantly better than uncrossed stereoacuity. 95% limits of test–retest agreement for crossed and uncrossed stereoacuities using the VDST were 0.27 and 0.30, respectively. An exact test–retest match using VDST was 84% in normals and 77% in abnormals for crossed and 83% in normal and 74% in abnormal for uncrossed stereoacuities.ConclusionVDST is a reliable, valid and easy-to-administer distance crossed and uncrossed stereoacuity measuring device. Further studies are required to establish the clinical importance of assessing these two forms stereoacuities in relation to various binocular vision disorders.

Model of a Support Vector Machine to Assess the Functional Cure for Surgery of Intermittent Exotropia

In this paper the optimum timing for the postoperative functional cure of basic intermittent exotropia is explored based on support vector machine (SVM). One hundred and thirty-two patients were recruited in this prospective cross-sectional study with 6 months of follow-up. Examinations included angle of deviation, central and peripheral fusion, controllability, and near and distance stereopsis. Influencing factors of postoperative alignment and stereopsis were analyzed with a chi-squared test and univariate and multivariate logistic regression analyses. At 6 months post-operation, there were 84 successful procedures for the angle of deviation, with 4 overcorrections and 44 undercorrections. The success rate was 63.6%. The angle of deviation on postoperative day 1 was the only significant associated factor. One hundred and thirty patients had normal near stereoacuity, 60 had normal distance stereoacuity according to a Functional Visual Analyzer assessment, and 108 had normal stereoacuity as assessed by the Frisby Davis Distance (FD2) stereotest. The age of onset and preoperative distance stereoacuity with FD2 were the influencing factors of postoperative distance stereopsis restoration. The accuracy of this method of SVM was 82.1%. The angle of deviation for distance on postoperative day 1 was the only significant factor that correlated with alignment at 6 months post-operation, and the model of SVM was useful to determine the optimal time of the postoperative functional cure.

The pursuit of stereopsis

Pediatric ophthalmologists are increasingly expected to promote, preserve, and restore binocular vision. Clinical studies on restoring alignment and stereopsis in the management of amblyopia, esotropia, exotropia, and complex strabismus are reviewed from the perspective of the author's published work and personal experiences. Treatment of amblyopia by means of optical rehabilitation, occlusion, or penalization has been reinforced by medical treatment and perceptual training with monocular or binocular video games. Studies indicate that early management of esotropia and alignment within 8Δ is required for regaining stereopsis. In the surgical management of intermittent exotropia, distance stereopsis by Frisby Davis Distance stereotest can predict better stereopsis, with patients having preoperative distance stereopsis of <70 arcsec less likely to improve after surgery. The surgeon's armamentarium for correcting alignment and restoring binocular vision include procedures such as adjustable, partial vertical rectus muscle transposition in cases of exotropic Duane syndrome and lateral rectus palsy, periosteal fixation of the globe or of the lateral rectus muscle, and medial transposition of the split lateral rectus muscle. The goal for present-day strabismologists is not merely to correct strabismus but also to achieve alignment of eyes in time to ensure normal development of stereopsis in children and to restore alignment and stereopsis in adults.

Evaluation of FD2 (Frisby Davis distance) stereotest in surgical management of intermittent exotropia

AimTo evaluate Frisby Davis distance (FD2) stereotest for determining the timing of surgical intervention in intermittent exotropia (X(T)).MethodsA prospective case–control study was conducted including 30 patients with X(T) and 30...

Effects of interpupillary distance on stereoacuity: the Frisby Davis distance stereotest versus a 3-dimensional distance stereotest

To evaluate the effect of interpupillary distance (IPD) on stereoacuity using 2 kinds of stereoacuity tests in a normal population. The distance stereoacuities of 33 healthy volunteers with no evidence of ocular diseases were measured with the Frisby Davis distance (FD2) stereotest and a 3-dimensional monitor-based distance stereotest (distance 3-D stereotest). These 2 kinds of stereotests were repeated using horizontal periscopes to increase the IPD 2- and 3-fold in order to investigate the effect of IPD increase on stereoacuity. The mean age of the participants was 28.5 years (range 20-41 years). The mean logarithms of the individual minimum angle of stereodiscrimination (logMAS) were 1.04 ± 0.23 (range 0.70-1.48 logMAS) with the FD2 stereotest and 1.52 ± 0.19 (range 1.00-1.85 logMAS) with the distance 3-D stereotest. As the IPD increased 2- and 3-fold, the logMAS measured with the FD2 stereotest improved from 1.04 to 0.98 and 0.91 (P = 0.061 and P = 0.003), respectively, and those measured with the distance 3-D stereotest worsened from 1.52 to 1.73 and 1.85 (P < 0.001 and P < 0.001), respectively. Changes in IPD measured with the FD2 stereotest exhibited opposite effects to those measured with the distance 3-D stereotest. This reflects what is known to happen in the real world, i.e., that stereoacuity improves as IPD increases.

Distance Stereoacuity by Frisby Davis Distance Stereotest after Surgery in Intermittent Exotropic Patients

Distance Stereoacuity by Frisby Davis Distance Stereotest after Surgery in Intermittent Exotropic Patients

Distance Stereotest Using a 3-Dimensional Monitor for Adult Subjects

To evaluate the validity and test-retest reliability of a contour-based 3-dimensional (3-D) monitor distance stereotest (distance 3-D stereotest) and to measure the maximum horizontal disparity that can be fused with disparity vergence for determining the largest measurable disparity of true stereopsis. Observational case series. Sixty-four normal adult subjects (age range, 23 to 39 years) were recruited. Contour-based circles (crossed disparity, 5000 to 20 seconds of arc; Microsoft Visual Studio C(++) 6.0; Microsoft, Inc, Seattle, Washington, USA) were generated on a 3-D monitor (46-inch stereoscopic display) using polarization glasses and were presented to subjects with normal binocularity at 3 m. While the position of the stimulus changed among 4 possible locations, the subjects were instructed to press the corresponding position of the stimulus on a keypad. The results with the new distance 3-D stereotest were compared with those from the distance Randot stereotest. The results of the distance 3-D stereotest and the distance Randot stereotests were identical in 64% and within 1 disparity level in 97% of normal adults. Scores obtained with the 2 tests showed a statistically significant correlation (r = 0.324, P = .009). The half-width of the 95% limit of agreement was 0.47 log seconds of arc (1.55 octaves) using the distance 3-D stereotest--similar to or better than that obtained with conventional distance stereotests. The maximum binocular disparity that can be fused with vergence was 1828 ± 794 seconds of arc (range, 4000 to 500). The distance 3-D stereotest showed good concordance with the distance Randot stereotest and relatively good test-retest reliability, supporting the validity of the distance 3-D stereotest. The normative data set obtained from the present study can serve as a useful reference for quantitative assessment of a wide range of binocular sensory abnormalities.

The use of distance stereoacuity assessment in determining the effectiveness of minus lenses in intermittent exotropia

Minus lens treatment has been advocated for intermittent exotropia to prevent progression and has been found to be effective in improving the control of the deviation in the distance. However, the effectiveness of this treatment is difficult to ascertain because of the lack of standardized outcome measures. Distance stereoacuity has been reported to be a reliable assessment of control of intermittent exotropia. In this study, its role as an outcome measure in the efficacy of minus lens treatment was examined by the use of the Frisby-Davis Distance stereotest. Patients (n = 24) with intermittent exotropia participated. Their distance stereoacuity was tested with the Frisby-Davis Distance stereotest at baseline and with varying minus lens powers (of -1, -2 and -3 D) that were tested randomly, as were the distance binocular visual acuity and angle of deviation. Varying minus lens powers had a significant effect on the angle of deviation and binocular visual acuity but not distance stereoacuity. However, both measures of binocularity, distance stereoacuity, and binocular visual acuity tended to diminish with the stronger minus lens power of -3 D. Participants actually demonstrated difficulty in accommodating through the stronger lenses. Distance stereoacuity (and binocular visual acuity) cannot reliably be used to determine the optimum minus lens strength that could be used in these patients to reduce the angle of deviation and regain binocularity in the distance. An additional observation was made that stronger lenses should perhaps be avoided to prevent binocular and visual discomfort.

Evaluation of factors influencing distance stereoacuity on Frisby–Davis Distance Test (FD2) in intermittent exotropia

AimTo evaluate the factors affecting the restoration of stereoacuity after surgery in cases of intermittent exotropia.MethodsThirty consecutive patients of intermittent exotropia X (T) scheduled for surgical intervention underwent preoperative evaluation,...

Development of distant stereoacuity in visually normal children as measured by the Frisby–Davis distance stereotest

Aims:To establish the range of normal distance stereoacuity and evaluate its development in visually normal children by using the Frisby–Davis distance stereotest (FD2).Methods:The distance stereoacuity of visually normal children aged...

Normal Distance Stereoacuity by Age Assessed by the Frisby Davis Distance Stereotest

Purpose: To determine the range of normal distance stereoacuity in populations with normal vision and the change of distance stereoacuity with age using the Frisby Davis Distance (FD2) stereotest and to evaluate the influence of monocular cues on the FD2 test. Methods: Ninety-eight subjects between 4 and 73 years old who had no ocular or neurologic diseases were examined. Distance stereoacuity was measured binocularly and monocularly with the FD2 test. Results: According to the results of the FD2 test, the mean distance stereoacuity of patients was 14.74±6.02 sec of arc. The monocular threshold with the dominant eye was 182.09±58.13 sec of arc. Subjects between 21 and 30 years old showed the best distance stereoacuity of 10.67±3.20 sec of arc. A significant decline in distance stereoacuity and monocular threshold were seen in subjects older than 61 (p

Real Depth vs Randot Stereotests

To compare the performance of real depth and Randot stereotests in strabismic and nonstrabismic patients. Observational case series. Stereoacuity was tested in 182 patients with a variety of strabismic conditions, using the Frisby-Davis 2 (FD2) distance stereotest, the near Frisby (nF) (both real depth tests), the Preschool Randot (nR), and Distance Randot (dR) tests (both based on Polaroid vectographs). Patients appreciated finer disparities with the nF test than the nR test at near and with the FD2 test than the dR test at distance. The type of stereotest influences measurable thresholds, and the results from different tests are not interchangeable. The choice of test should depend on the question being asked; nF and FD2 would be appropriate for determining presence or absence of stereopsis and best measurable stereopsis. The more rigorous Randot tests would be appropriate for determining subtle changes.