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Stereopsis assessment at multiple distances with an iPad application

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Abstract

We present a new application for iPad for screening stereopsis at multiple distances that allows testing up to ten levels of stereoacuity at each distance. Our approach is based on a random dot stereogram viewable with anaglyph spectacles. Sixty-five subjects with no ocular diseases, wearing their habitual correction were measured at 3 m and 0.5 m. Results were compared with a standard stereoscopic test (TNO). We found not statistically significant differences between both tests, but our method achieved higher reproducibility. Applications in visual screening programs and to design and use of 3D displays, are suggested.

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... Handheld mobile terminals have been used as effective instruments for evaluating stereopsis. Rodríguez-Vallejo et al. established a stereoacuity test called TST, performed on an iPad application [24]. Bonfanti et al. presented a "stereo acuity test using a smartphone inserted into a Google Cardboard" [25]. ...
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Owing to the limitations of printed stereoacuity tests, the effects of luminance and contrast on stereopsis have not yet been sufficiently investigated, despite its important implications in designing stereoacuity measuring instruments, particularly for electronic devices. A stereopsis measurement system was established using two 4 K smartphones and a phoropter to evaluate the effects of luminance and contrast variations on the stereoacuity test. Seventeen young subjects with normal visual acuity and stereopsis were recruited. Two types of test symbols, contour-based and random-dot-based, were used in the experiment. Four series tests were established with different maximum brightness values, including 240 lux, 120 lux, 60 lux, and 30 lux. Each series test contained 19 pages with different contrasts between 95% and 5% and was calculated using the Michelson contrast formula. No significant difference was found for both contour-based and random-dot-based stereograms in any of the contrast groups with different maximum brightness. Similarly, no significant difference was found between contour-based and random-dot-based patterns under different contrasts of above 35%. As the contrast decreased below 30%, the stereopsis was significantly better in the contour-based pattern than in the random-dot-based pattern for some degrees of contrast. The luminance and contrast of the digital display are not critical factors for stereoacuity under normal circumstances. This implies that a standard monitor with a certain 3D technology can be used to measure the stereoacuity threshold without calibrating the luminance and contrast.
... La espectrofotometría es una técnica con un gran potencial de aplicación que ha permitido un fuerte desarrollo en los ámbitos industrial e I+D+i, pero su presencia en el ámbito docente, estudiantil, personal y amateur se ve limitada por su elevado coste, la especificidad de los equipos comerciales y la baja accesibilidad. Esta técnica tiene aplicaciones muy diversas que van desde la caracterización de cuerpos celestes en astronomía (Sterken, 1992) (Itoh, 2017) hasta la detección de componentes químicos en un laboratorio (Schwedt, 1997) (Binks, 2017), pasando por la caracterización y calibrado de pantallas led (Rodríguez-Vallejo, 2017). ...
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Resumen En este trabajo se detalla el proceso de diseño, desarrollo y prototipado de un sistema de medida del espectro visible. El objetivo que hay que cumplir es la obtención de un dis-positivo reproducible, competitivo en el aspecto técnico con modelos comerciales de docencia actuales, y económico. El dispositivo resultante reúne las características de ser por-tátil, versátil, compacto, económico y con alta conectividad. El centro del proyecto es el software, que como caracterís-tica clave permite ser utilizado prácticamente con cualquier cámara comercial y ser ejecutado desde distintos sistemas operativos. El prototipado se ha realizado con una cáma-ra comercial con conexión USB con el fin de encontrar un equilibrio entre asequibilidad y resolución del producto final. Tiene un precio 20 veces más económico y una resolución similar al espectrofotómetro comercial utilizado como refe-rencia. Palabras clave Espectrofotómetro, red de difracción, impresión 3D. Abstract In this work, the processes of designing, developing and prototyping an instrument to measure the visible spectrum is shown in detail. The objective is to obtain a low-cost device, reproducible and technically competitive with the commercial docent models. The obtained device is portable, adaptable, compact, economic and with high connectivi-ty. The core of the project is the software, and its key point is the compatibility with any commercial camera and it can be run in different operative systems. For this prototype a commercial camera with USB connection has been considered in order to find a balance between price and resolution for the resulting device.
... Psychophysical tests have been carried out on mobile devices with custom applications that implement specific tests such the assessment of visual acuity (Black et al., 2013), contrast sensitivity (Dorr, Lesmes, Lu, & Bex, 2013;Rodríguez-Vallejo, Remón, Monsoriu, & Furlan, 2015;Kollbaum, Jansen, Kollbaum, & Bullimore, 2014), chromatic contrast sensitivity (Bodduluri, Boon, Ryan, & Dain, 2018) or stereoacuity (Rodríguez-Vallejo, Ferrando, Montagud, Monsoriu, & Furlan, 2017), or using an application that allows the sequential presentation of images created offline (Turpin, Lawson, & McKendrick, 2014;McKendrick et al., 2018;Nguyen et al., 2018). To our knowledge, there are no software applications for mobile devices that allow the flexible generation of stimuli to create a wide range of psychophysical tests, and this motivated us to create StimuliApp, an open-source application developed natively for iPadOS and iOS, in which the user can create psychophysical tests by means of a system of menus. ...
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Psychophysical tests are commonly carried out using software applications running on desktop or laptop computers, but running the software on mobile handheld devices such as smartphones or tablets could have advantages in some situations. Here, we present StimuliApp, an open-source application in which the user can create psychophysical tests on the iPad and the iPhone by means of a system of menus. A wide number of templates for creating stimuli are available including patches, gradients, gratings, checkerboards, random-dots, texts, tones or auditory noise. Images, videos and audios stored in files could also be presented. The application was developed natively for iPadOS and iOS using the low-level interface Metal for accessing the graphics processing unit, which results in high timing performance.
... The present work is timely, as a number of other tabletbased tests have recently been reported, designed to measure various more basic aspects of visual function, such as visual acuity, 15,41,43,44 contrast sensitivity, 45-49 visual fields, 12,50-56 stereopsis, 57 and colour vision. 58,59 What distinguishes the tests described in the present study is that they are intended to measure 'high-level' function on everyday tasks. ...
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Purpose: To describe, refine, evaluate, and provide normative control data for two freely available tablet-based tests of real-world visual function, using a cohort of young, normally-sighted adults. Methods: Fifty young (18-40 years), normally-sighted adults completed tablet-based assessments of (1) face discrimination and (2) visual search. Each test was performed twice, to assess test-retest repeatability. Post-hoc analyses were performed to determine the number of trials required to obtain stable estimates of performance. Distributions were fitted to the normative data to determine the 99% population-boundary for normally sighted observers. Participants were also asked to rate their comprehension of each test. Results: Both tests provided stable estimates in around 20 trials (~1-4 min), with only a further reduction of 14%-17% in the 95% Coefficient of Repeatability (CoR95 ) when an additional 40 trials were included. When using only ~20 trials: median durations for the first run of each test were 191 s (Faces) and 51 s (Search); test-retest CoR95 were 0.27 d (Faces) and 0.84 s (Search); and normative 99% population-limits were 3.50 d (Faces) and 3.1 s (Search). No participants exhibited any difficulties completing either test (100% completion rate), and ratings of task-understanding were high (Faces: 9.6 out of 10; Search: 9.7 out of 10). Conclusions: This preliminary assessment indicated that both tablet-based tests are able to provide simple, quick, and easy-to-administer measures of real-world visual function in normally-sighted young adults. Further work is required to assess their accuracy and utility in older people and individuals with visual impairment. Potential applications are discussed, including their use in clinic waiting rooms, and as an objective complement to Patient Reported Outcome Measures (PROMs).
... IPad application was used to evaluate stereopsis at multiple distance. Rodríguez-Vallejo et al. presented a new stereoacuity test, called TST, performed on an iPad (2048-by-1536-pixel resolution and 264 ppi) [27]. e identified mission was almost the same with the TNO test. ...
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Background: The advantage of using an autostereoscopic smartphone is that it can achieve 3D effects without the need for glasses. The purpose of this study was to evaluate whether this technology could be utilized to detect stereoacuity. Methods: An autostereoscopic smartphone was used to imitate Lang stereotest I & II, Pass Test 3, Dinosaur Stereoacuity Test, and the Random Dot Stereo Acuity Test to screen the stereopsis of children from 3-6 years old. Results: No significant difference was found between each pair of groups (autostereoscopic smartphone vs. Lang stereotest I, Lang stereotest II, Pass Test 3, Dinosaur Stereoacuity Test, and Random Dot Stereo Acuity Test, respectively; Wilcoxon signed-rank test, P value all >0.05). All of the weighted kappa were higher than 0.84. Therefore, all of the comparisons between measurements showed a high level of agreement. Conclusions: The autostereoscopic smartphone is an effective tool when used for the screening of deficiency in stereopsis.
... 18,19 Thus, a number of tablet-based apps have recently been developed for measuring visual field loss, 20-26 as well as other aspects of visual function such as visual acuity (VA), [27][28][29][30] contrast sensitivity (CS), [31][32][33][34][35] foveal defects, 36 and stereopsis. 37 The hope is that these tests could be used as an alternative to traditional, more expensive tests, or could allow patients to be monitored more regularly from the comfort of their own homes. This could bring considerable benefits in terms of reduced healthcare costs, an improved patient experience, and the ability to detect high-risk individuals more quickly than traditional (i.e., annual or biannual) monitoring regimens. ...
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Purpose: Visual field (VF) examination by standard automated perimetry (SAP) is an important method of clinical assessment. However, the complexity of the test, and its use of bulky, expensive equipment makes it impractical for case-finding. We propose and evaluate a new approach to paracentral VF assessment that combines an inexpensive eye-tracker with a portable tablet computer ("Eyecatcher"). Methods: Twenty-four eyes from 12 glaucoma patients, and 12 eyes from six age-similar controls were examined. Participants were tested monocularly (once per eye), with both the novel Eyecatcher test and traditional SAP (HFA SITA standard 24-2). For Eyecatcher, the participant's task was to simply to look at a sequence of fixed-luminance dots, presented relative to the current point of fixation. Start and end fixations were used to determine locations where stimuli were seen/unseen, and to build a continuous map of sensitivity loss across a VF of approximately 20°. Results: Eyecatcher was able to clearly separate patients from controls, and the results were consistent with those from traditional SAP. In particular, mean Eyecatcher scores were strongly correlated with mean deviation scores (r2 = 0.64, P < 0.001), and there was good concordance between corresponding VF locations (∼84%). Participants reported that Eyecatcher was more enjoyable, easier to perform, and less tiring than SAP (all P < 0.001). Conclusions: Portable perimetry using an inexpensive eye-tracker and a tablet computer is feasible, although possible means of improvement are suggested. Translational relevance: Such a test could have significant utility as a case finding device.
... Random dot stereograms are thought to be a more robust clinical technique as the object seen if stereopsis is present cannot be determined from changes in head position and other monocular cues (Heron and Lages, 2012). Stereopsis is more precise at near and therefore is generally assessed at close distance (Rodríguez-Vallejo et al., 2017). ...
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To evaluate fusion stereopsis in patients with intermittent exotropia before and after strabismus surgery. Fifty-three patients (mean age: 11.8 years, range: 5 to 25 years) with intermittent exotropia were enrolled. Fusion was measured with the Worth 4-dot test. Near stereopsis was examined with Titmus and stereoscopic test charts (created in China by Shao-Ming Yan). Distance stereopsis was tested with random-dot stereograms produced by Tianjin Eye Hospital. All patients completed the tests preoperatively and 2 and 6 weeks postoperatively. There were no statistically significant differences in stereoscopic test charts among groups preoperatively (P > .05) and postoperatively (P > .05) or on Titmus tests preoperatively (P > .05) and postoperatively (P > .05). Among 53 patients, the percentage of distance stereoscopic improvement was 49% after 2 weeks and 77% after 6 weeks compared to 13% preoperatively. Six weeks postoperatively, random-dot stereograms were significantly different in those younger than 7 years and older than 13 years (P < .05), as well as those 7 to 13 years and older than 13 years (P < .05). Fifty (94%) demonstrated peripheral fusion and only 21 (40%) demonstrated central fusion preoperatively. Six weeks postoperatively, all patients exhibited peripheral fusion and 52 (98%) demonstrated central fusion. Central fusion in patients with intermittent exotropia significantly increased after 6 weeks (chi-square = 42.29, P < .01). Patients with intermittent exotropia have good near stereoacuity preoperatively and postoperatively. Even if surgery is postponed until adolescence, distance stereopsis can still be recovered. Surgical intervention can restore central fusion and stereoacuity in patients with intermittent exotropia. [J Pediatr Ophthalmol Strabismus. 2015;52(1):52-57.]. Copyright 2015, SLACK Incorporated.
Article
This study measured aniseikonia before and after the first and second cataract surgeries in ametropic adults. The relationship of aniseikonia to anisometropia and its effect on stereopsis, ocular alignment, and clinical symptoms were determined. Seventeen patients scheduled to have bilateral cataract surgery with 2 diopters or more ametropia participated. Patients were evaluated before cataract surgery and 4 weeks (±1 week) after the first and second surgery. Visual acuity, refractive error, aniseikonia, stereopsis, ocular alignment, and visual symptoms were determined at each visit. Aniseikonia increased after the first cataract surgery. The increase in aniseikonia occurred in concert with increased anisometropia and resulted in poorer stereopsis overall. Aniseikonia and anisometropia 1 month (±1 week) after the second cataract surgery returned to near baseline and were associated with better stereopsis. The amount of aniseikonia showed substantial variance and could not be predicted by the amount of induced anisometropia. Changes in ocular alignment were minimal. Statistically significant changes in patient symptoms between study visits were infrequent. Aniseikonia induced by cataract surgery may not be a substantial problem for ametropic adults with normal binocular vision, at least in the short term.
Article
Recent literatures related to the evaluations of visual fatigue induced by stereoscopic images (VFSI) are reviewed with the short introduction of cortical mechanisms related to early visual processing, vergence eye movement and lens accommodation. Based on this knowledge, the requirements to prevent visual fatigue and discomfort induced by viewing stereoscopic images were sought. Firstly, the careful alignment in the right/left eye images is required for the stereoscopic vision without discomfort. Secondly, the conflict between the demands for vergence eye movement and lens accommodation in the near response should be avoided, by using modest binocular disparity. Thirdly, the frequency of changes in binocular disparity should be restricted. Finally, the appropriate viewing distance is also recommended to avoid visual fatigue.
Article
Principles of the design and administration of clinical stereopsis tests are outlined. Once the presence of the distinct sense of the third dimension by binocular vision alone and without help from monocular cues has been established in a patient, the examination can proceed to the measurement of stereoscopic acuity. Best results are obtained with high-contrast, sharp, well-articulated and uncrowded elements from easily-recognized target sets, displayed with no time constraints. Polarization is the preferred method of right/left eye separation; time-sharing at a minimum of 60 Hz on computer displays with counterphase occluding goggles is a feasible procedure. Random-dot stereograms are problematic because not all observers can disentangle the coherent global disparity on a first view.
Article
Tests of stereopsis have many uses in ophthalmic practice, especially in the examination of children. Stereotests are recommended as a way to improve paediatric vision screening programs, to provide an overall indication of binocularity and to monitor binocularity in amblyopia therapy or contact lens monovision. There are currently many stereotests available to practitioners and careful consideration must be given to the applicability of a particular test. The correct stereotest for a particular task is critically dependent on the perceptual age of the patient and the type of information the clinician wants to gather from the test.
Article
Reports of dissimilar stereothresholds for contour and random-dot (RD) targets may reflect differences in stimulus properties or differences between local and global stereoscopic processing mechanisms. In this study, we evaluated whether the stereothresholds obtained using low- and high-density RD stimuli are consistent with a distinction between local and global disparity processing. Stereothresholds were measured in eight normal subjects for a small disparate line segment superimposed on RD surrounds with densities that ranged between 0.07 and 28.3%. Stereothresholds averaged 0.23 arc min for an RD density of 0.39% and approximately doubled for lower and higher densities. The increase in stereothresholds at low densities is likely because of the increased spacing between elements, which reduces their usefulness as a reference for relative disparity judgments. The increase in stereothresholds at high densities is attributed to a crowding effect. Because the stereothresholds measured with RD stimuli of low and high density are limited by different constraints, they can be considered to be different types of stereotargets. However, because the stereothresholds measured for RD targets of varying densities are similar to those determined previously for a local, two-rod stereotarget, it is likely that all these stimuli are processed by a single disparity-processing mechanism.
Article
Measurement of distance stereoacuity may be useful in assessing strabismic patients, especially those with intermittent exotropia. We developed the Distance Randot Stereotest as an easily administered quantitative test for distance stereoacuity in children. By using a prototype, we reported testability, validity, and normative data. Here we report normative and validity data for the final, commercially available version of the test. We administered both the Prototype and the Final Version Distance Randot Stereotest to 156 normal volunteers (2-40 years of age) and 77 strabismic patients (4-62 years of age). Test-retest data were collected for the Final Version. Normative Final Version scores were similar to those obtained with the Prototype; 96% were < or = 100 arcsec. Test-retests were identical in 82% and within one disparity level in 100%. Final Version scores were correlated with Prototype scores (rs = 0.64, p < 0.001). Among strabismic patients, 62.3% had abnormal stereoacuity; those with normal scores had incomitant or intermittent deviations. Nil stereoacuity was found in 27 patients, confirmed in 90.9% of retests; 17 had measurable stereoacuity, confirmed in 96.3% of retests. Patients with constant strabismus were more likely to have nil stereoacuity than patients who had intermittent strabismus (95% vs 12.2%). Distance Randot scores from normal subjects have low variability within each age group and high test-retest reliability. There is little overlap between Distance Randot scores from normal control and strabismic patients. The Distance Randot Stereotest is a sensitive measurement of binocular sensory status that may be useful in monitoring progression of strabismus and/or recovery after strabismus surgery.
Article
This paper presents a general statistical methodology for the analysis of multivariate categorical data arising from observer reliability studies. The procedure essentially involves the construction of functions of the observed proportions which are directed at the extent to which the observers agree among themselves and the construction of test statistics for hypotheses involving these functions. Tests for interobserver bias are presented in terms of first-order marginal homogeneity and measures of interobserver agreement are developed as generalized kappa-type statistics. These procedures are illustrated with a clinical diagnosis example from the epidemiological literature.
Article
In this investigation, carried out under a Youth Health Care postgraduate course in Nijmegen, the stereopsis of a school population of 730 children, aged 4-18 years, was recorded and clinically evaluated. Stereopsis was measured using the TNO test, a random-dot stereo test especially designed for the early detection of amblyopia. The main aims of this study were to establish the validity of the TNO test as a screening test for amblyopia, obtain information about the variability and age dependence of stereopsis, and to evaluate the efficacy of amblyopia prevention. The most important findings can be summarized as follows: 1. All amblyopes are detected by the TNO test's recommended referral criterion of 240 sec arc (binocular threshold parallax in sec arc). 2. The red-green anaglyphs used in the test do not pose problems for individuals with a colour vision deficiency. 3. The ability to discriminate depth improves by a factor of two over the age interval 4-12 years. 4. A stereoacuity of < or = 120 sec arc is a good predictor of normal or correctable normal vision, and may therefore help in evaluating the often incomplete results of eye tests of young children. 5. Where there is an increased perinatal risk, there is a greater chance of disturbed binocular vision. 6. It is estimated that 75% of amblyopes remain amblyopic, possibly because of delayed detection; 60% of the amblyopes in the population examined were not identified before the age of 5 years.
Article
To determine the efficacy of distance stereotesting as a screening device. Distance stereoacuity using the global Random Dot and contour Circle test of the Mentor BVAT II-SG computerized testing system was measured for 216 patients, ages 6 to 18 years, before the clinical examination. Patients were classified into pass/fail groups in the areas of refractive error change (REC), ocular deviation (DEV), visual acuity (VA), and all three together (EXAM). Legitimate cutoff scores were obtained when patients were classified as 'pass' as follows: REC if the change was 0.50 D or less in sphere or cylinder relative to the habitual correction or to emmetropia if no habitual correction; DEV if there was no heterophoria or strabismus at distance (criteria of heterophoria of < 6 prism diopters and heterophorias of any magnitude were also tested); VA if the acuity at distance was better than or equal to 20/25 in the poorer eye and better than or equal to 20/20 in the better eye; EXAM if they were pass in REC, DEV, and VA. Optimal pass/fail cutoff values for the stereopsis measurements were determined by finding the maximum chi2 value from contingency tables constructed using pass/fail levels for the screening test at each of the observed levels. The pass rates for REC, DEV, VA, and EXAM were 45%, 72%, 42%, and 24%, respectively. Patients passed the BVAT at the analytically determined optimal cutoff values of less than or equal to 120 sec arc for global and less than or equal to 30 sec arc for contour stereopsis. The sensitivity and specificity for global stereopsis were 0.90 and 0.40 for REC, 0.89 and 0.30 for DEV, 0.93 and 0.51 for VA, and 0.87 and 0.63 for EXAM. For contour stereopsis, the corresponding values were 0.85 and 0.42, 0.89 and 0.34, 0.91 and 0.53, and 0.84 and 0.62. Distance stereotesting is highly sensitive to small refractive error changes, heterophorias and strabismus, visual acuities < 20/25, or any of the three. Global stereopsis is only slightly better than contour stereopsis at classifying patients. Distance stereotesting has potential as an effective screening test.
Article
To examine how stereoacuity changes with age as measured by a variety of stereotests. Stereoacuity has been measured in 60 normal subjects aged 17-83 years by a single observer using TNO, Titmus, Frisby near, and Frisby-Davis distance stereotests. Motor fusion was measured at (1/3) metre and 6 metres. Overall stereoacuity measured by all tests showed a mild decline with age (p<0.001 for all tests; Spearman rank correlation). A marked reduction to screening or absent levels of stereoacuity was seen in five subjects aged over 55, but only with the TNO stereotest. All these subjects were able to achieve a stereoacuity of 200 seconds of arc or better with the Titmus test and 340 seconds of arc or better using the Frisby near stereotest. There was a small decline with age in the base out motor fusion range measured at 6 metres (p<0.05; Spearman rank correlation). No subject described difficulty in judging distances for everyday tasks. Although subjects showed some decline in stereoacuity with age by all tests, the large drop in stereoacuity seen in some older subjects using the TNO test was probably due to difficulty overcoming the dissociative effect of the test rather than a true reduction in cortical disparity detection. Results of random dot stereotests should be interpreted with caution in older patients, particularly with respect to their ability to perform everyday visual tasks.
Article
Poor control of intermittent exotropia has been considered an indication for surgical intervention, and poor distance stereoacuity may be an indicator of poor control. Two new measures of distance stereoacuity, the Frisby-Davis Distance test (FD2) and Distance Randot test (DR), both of which have been validated in normal and strabismic subjects, were evaluated, and we compared stereoacuity with scores on a recently described control scale. Prospective case series. Twenty-five consecutive patients with intermittent exotropia. Office-based control was graded at distance and near on a 0 to 5 scale, and distance control ranged from 1 (recovery in 1-5 seconds after monocular occlusion) to 4 (>50% spontaneously tropic). Stereoacuity was measured using the FD2 and DR at distance and the Preschool Randot and Frisby tests at near. Distance stereoacuity measured using the FD2 and DR. Measurable distance stereoacuity thresholds in intermittent exotropia were poor with the DR and excellent with the FD2 (medians, nil and 40''; P<0.0001). Near stereoacuity was excellent with both the Preschool Randot and Frisby (medians, 60'' and 60''; P = 0.99). There was poor correlation between distance control score and either FD2 (r(s) = 0.1, P = 0.6) or DR (r(s) = 0.3, P = 0.2). Control scores correlated with magnitude of deviation at distance (r(s) = 0.5, P = 0.02) and near (r(s) = 0.5, P = 0.01). The real-world contour-based targets of the new distance FD2 appear to stimulate fusion in intermittent exotropia, even when distance control is poor. In contrast, the new Polaroid vectograph-based DR is very sensitive to disturbances of binocularity. Two new distance stereoacuity tests appear sensitive to opposite ends of the intermittent exotropia spectrum; FD2 performance deteriorates when the patient is constantly tropic, whereas DR performance deteriorates at the earliest stages of intermittency.
Pediatric eye and vision examination Optometric Clinical Practice Guideline TNO stereopsis test as an aid to the prevention of amblyopia
  • J American Optometric Association
  • P Walraven
  • Janzen
American Optometric Association. Pediatric eye and vision examination. Optometric Clinical Practice Guideline. 1994. [8] J. Walraven, P. Janzen, TNO stereopsis test as an aid to the prevention of amblyopia, Ophthal. Physiol. Optics 13 (1993) 350–356. [9] S. Heron, M. Lages, Screening and sampling in studies of binocular vision, Vision Res. 62 (2012) 228–234.
Westheimer, Clinical evaluation of stereopsis
[10] G. Westheimer, Clinical evaluation of stereopsis, Vision Res. 90 (2013) 38–42.
Inter-Display Reproducibility of Contrast Sensitivity Measurement with iPad A pilot trial of the iPad tablet computer as a portable device for visual acuity testing
  • M Rodríguez-Vallejo
  • J A Monsoriu
  • W D Furlan
[16] M. Rodríguez-Vallejo, J.A. Monsoriu, W.D. Furlan, Inter-Display Reproducibility of Contrast Sensitivity Measurement with iPad. Optom. & Vis. Sci., 93(12) (2016) 1532-1536. [17] Z.T Zhang, S.C Zhang, X.G. Huang, L.Y. Liang, A pilot trial of the iPad tablet computer as a portable device for visual acuity testing. J Telemed Telecare, 19 (1) (2013) 55–59.
Visual acuity and contrast sensitivity screening with a new iPad application Crosstalk in stereoscopic displays: a review
  • W D Quintana
  • J A Furlan
  • Monsoriu
[20] M. Rodríguez-Vallejo, C. Llorens-Quintana, W.D. Furlan, J.A. Monsoriu, Visual acuity and contrast sensitivity screening with a new iPad application. Displays 44 (2016) 15-20. [21] A. J. Woods, Crosstalk in stereoscopic displays: a review. J. Electron. Imag., 21 (2012), 040902-040902.