Modified Test Protocol Improves Sensitivity of the Stereo Fly Test

A comparative study of stereopsis in term and preterm children with and without retinopathy of prematurity

PURPOSE

To evaluate stereopsis in term-born, preterm, and preterm children with and without retinopathy of prematurity (ROP) and its treatment.

METHODS

The cross-sectional study included 322 children between 3 and 11 years of age born term or preterm, with or without ROP, and with or without treatment for ROP. The ROP treatments were laser therapy, intravitreal injection (IVI) of anti-vascular endothelial growth factor, or their combination. Stereoacuity was measured using the Titmus Stereo Test, and the results among various age groups were analyzed.

RESULTS

Stereopsis was found to improve with increasing age at testing (P < 0.001) across the entire study population. The term group exhibited significantly better stereoacuity than the preterm group (P < 0.001). At 3-5 years and 6-8 years, the preterm children without ROP exhibited significantly better stereoacuity than did those with ROP (P < 0.001 and P = 0.02, respectively); however, at 9-11 years, both groups exhibited similar stereoacuity (P = 0.34). The stereoacuity in the children with untreated ROP was similar to that of the children with treated ROP in all age groups (P > 0.05). No significant differences in stereopsis were identified between children with ROP treated with laser versus with IVI (P > 0.05). From multivariate analysis, younger age at testing (P = 0.001) and younger gestational age (P < 0.001) were associated with poorer stereopsis.

CONCLUSIONS

Stereopsis development gradually improved with age in all groups. The children born preterm exhibited poorer stereoacuity than those born term. Children with ROP treated with laser photocoagulation versus IVI may exhibit similar levels of stereoacuity. Younger age at testing and gestational age were independent risk factors for poorer stereoacuity.

Test retest variability in stereoacuity measurements

Background: A clinician's choice of stereotest is influenced by the robustness of the measurement, in terms of sensitivity, specificity and test-retest variability. In relation to the latter aspect, there are limited data on the test-retest variability of these new tests and how they compare to the more commonly used stereotests. Therefore, the aim of the study was to determine the test-retest variability of four different measures of stereoacuity (TNO, Frisby, Lang Stereopad and Asteroid (Accurate STEReotest On a mobIle Device)) and to compare the stereoacuity measurements between the tests in an adult population. Methods: Stereoacuity was measured twice using TNO, Frisby, Lang Stereopad and Asteroid. Inclusion criteria included adult participants (18 years and older), no known ophthalmic condition and VA (Visual Acuity) equal to or better than 0.3 logMAR (Logarithm of the Minimum Angle of Resolution) with interocular difference of less than 0.2 logMAR. Bland-Altman analysis was used to assess agreement within and between stereotests. Differences in stereo thresholds were compared using signed Wilcoxon tests. Results: Fifty-four adults (male: 23 and female: 31) with VA equal to or better than 0.3 logMAR in either eye and interocular difference less than 0.2 logMAR were assessed (mean age: 38 years, SD: 12.7, range: 18-72). The test-retest variability of all the clinical stereotests, with the exception of the Lang Stereopad (p = .03, Wilcoxon signed-rank test), was clinically insignificant as the mean bias was equal or less than 0.06 log seconds of arc (equivalent to 1.15 seconds of arc). While the Asteroid test had the smallest variation between repeated measures (mean bias: -0.01 log seconds of arc), the Frisby and Lang Stereopad tests had the narrowest and widest limits of agreement respectively. When comparing results between tests, the biggest mean bias was between Frisby and Lang Stereopad (-0.62 log seconds of arc), and 64.8% and 31.5% of differences were in the medium (21-100" of arc) and larger (>100" of arc) ranges respectively. Conclusion: The TNO and Frisby tests have good reliability but measure stereoacuity over a narrower range compared to the Asteroid which shows less variation on repeated testing but has a larger testing range. The data reported here show varying degrees of agreement in a cohort of visually normal participants, and further investigation is required to determine if there is further variability when stereoacuity is reduced.

Technologies supporting vision screening: a protocol for a scoping review

INTRODUCTION

Vision problems affect academic performance, social and mental health. Most traditional vision screening methods rely on human expert assessments based on a set of vision tests. As technology advances, new instruments and computerised tools are available for complementing vision screening. The scoping review based on this protocol aims to investigate current technologies for vision screening, what vision tests can be complemented by technologies, and how these can support vision screening by providing measurements.

METHODS AND ANALYSIS

The planned review will utilise the PRISMA extension for Scoping Reviews (PRISMA-ScR) tool. Electronic search will be performed in databases, including Web of Science, MEDLINE (Ovid), Scopus, Engineering Village, Cochrane and Embase. We will perform a systematic search in selected reference databases without the limitation on publications dates, or country of studies. Reference management software, like EndNote and DistillerSR, will be used to remove duplicate entries. Two authors will independently analyse the studies for inclusion eligibility. Conflicts will be resolved by discussion. We will extract the types of technologies, types of vision tests they complement and the measurements for the included studies. Overall findings will be synthesised by thematic analysis and mapping to the logic model.

ETHICS AND DISSEMINATION

Ethical approval is not required for this review, as it will only summarise existing published data. We will publish the findings in an open access, peer-reviewed journal. We expect that the review results will be useful for vision screening experts, developers, researchers, and policymakers.

Perceptual Coupling Based on Depth and Motion Cues in Stereovision-Impaired Subjects

When an object is partially occluded, the different parts of the object have to be perceptually coupled. Cues that can be used for perceptual coupling are, for instance, depth ordering and visual motion information. In subjects with impaired stereovision, the brain is less able to use stereoscopic depth cues, making them more reliant on other cues. Therefore, our hypothesis is that stereovision-impaired subjects have stronger motion coupling than stereoscopic subjects. We compared perceptual coupling in 8 stereoscopic and 10 stereovision-impaired subjects, using random moving dot patterns that defined an ambiguous rotating cylinder and a coaxially presented nonambiguous half cylinder. Our results show that, whereas stereoscopic subjects exhibit significant coupling in the far plane, stereovision-impaired subjects show no coupling and under our conditions also no stronger motion coupling than stereoscopic subjects.

The difference of distance stereoacuity measured with different separating methods

Background

The majority of tests to evaluate stereopsis should separate two eyes first. Whether different binocular separating manner may affect the test result of stereopsis is the main purpose of this study. Red-green anaglyphs, polarized light technology, active shutter 3D system, and auto-stereoscopic technique were chosen to evaluate distance stereoacuity.

Methods

Red-green anaglyphs test system was established with an ASUS laptop with the aid of TNO Stereotest glasses. Active shutter 3D system was set up with the same ASUS laptop with the aid of NVidia 3D Vision 2 Wireless Glasses Kit. The polarized 3D system adopted the AOC display. A Samsung naked-eye 3D laptop was used to set up an auto-stereoscopic system. Thirty subjects were recruited. Distance stereoacuity was measured with those computer systems.

Results

The auto-stereoscopic system was failed to measure distance stereopsis. A significant difference was found among red-green anaglyphs, polarized 3D system, and active shutter 3D system (Friedman Test, Chi-square =48.713, P<0.001). No significant difference was found between the polarized 3D system and an active shutter 3D system (Z=-1.134, P=0.257). The stereoacuity of the red-green glasses test was significantly worse than those of the other two test systems (versus shutter 3D test, Z=-4.553, P<0.001; versus polarized 3D test, Z=-4.618, P<0.001).

Conclusions

Different separating methods may affect the test result of distance stereopsis.

Binocular non-stereoscopic cues can deceive clinical tests of stereopsis

Stereoscopic vision plays a critical role in visual perception; however, it is difficult to assess. In clinical settings, stereoacuity is assessed with clinical stereotests. Observers can use monocular cues to deceive some of the most common stereotests, such as the Titmus test. The Randot test has been found free of monocular cues, and here we confirm that result by testing observers under monocular viewing. However, there is a common misconception that only monocular cues can be used to deceive stereotests. Here we demonstrate that binocular non-stereoscopic cues can also be used to pass the Randot, by testing participants with the test rotated, a condition that abolishes stereopsis, and comparing the performance to a monocular viewing condition. We also assessed the Random Dot Butterfly test and discovered considerable amounts of non-stereoscopic cues, including binocular cues in the Circles that can be used to deceive the test. Participants with amblyopia had more difficulty using non-stereoscopic cues than neurotypical observers. We gathered normal-viewing Randot stereoacuities for 110 participants (90 neurotypical and 20 with amblyopia) and compared them to psychophysical stereoacuities (our gold standard). The Randot test showed low positive normalized predictive values for detecting stereoblindness. It could perfectly detect stereo-impairment but with a low sensitivity.

The prevalence and diagnosis of 'stereoblindness' in adults less than 60 years of age: a best evidence synthesis

PURPOSE

Stereoscopic vision (or stereopsis) is the ability to perceive depth from binocular disparity - the difference of viewpoints between the two eyes. Interestingly, there are large individual differences as to how well one can appreciate depth from such a cue. The total absence of stereoscopic vision, called 'stereoblindness', has been associated with negative behavioural outcomes such as poor distance estimation. Surprisingly, the prevalence of stereoblindness remains unclear, as it appears highly dependent on the way in which stereopsis is measured.

RECENT FINDINGS

This review highlights the fact that stereopsis is not a unitary construct, but rather implies different systems. The optimal conditions for measuring these varieties of stereoscopic information processing are discussed given the goal of detecting stereoblindness, using either psychophysical or clinical stereotests. In that light, we then discuss the estimates of stereoblindness prevalence of past studies.

SUMMARY

We identify four different approaches that all converge toward a prevalence of stereoblindness of 7% (median approach: 7%; unambiguous-stereoblindness-criteria approach: 7%; visual-defect-included approach: 7%; multiple-criteria approach: 7%). We note that these estimates were derived considering adults of age <60 years old. Older adults may have a higher prevalence. Finally, we make recommendations for a new ecological definition of stereoblindness and for efficient clinical methods for determining stereoblindness by adapting existing tools.

Stereopsis: are we assessing it in enough depth?

The assessment of stereoacuity is an integral part of the ophthalmic assessment, with the responses used to inform clinical management decisions. Stereoacuity impacts on many aspects of life, but there are discrepancies reported where people without measurable stereoacuity report appreciating 3-D vision. This could be due, in part, to the presentation of the stimuli. A literature review was undertaken to evaluate current assessment techniques, how they relate to patient outcomes, identify the limitations of current tests and discuss how they could be improved. Recent evidence has been collated on currently available tests, used commonly within vision clinics, with normative data provided allowing responses to the tests to be interpreted. The relevance of the results is evaluated in relation to a range of outcomes, where a reduced level of stereopsis has a negative impact on the ability of an individual to perform many tasks, and can lead to an increase in difficulty interacting in the world. Current tests are limited in the aspects of stereoacuity they assess and their ability to precisely measure stereopsis. The world is not static, yet clinical tests are limited to measuring static stereoacuity, even though higher grades of depth perception can be identified in the presence of changing depth. Presentation methods of stereoacuity tests have remained similar over time, with a limited number of disparity levels assessed. New assessment methods are becoming available that include automated staircase testing to present multiple levels of disparity using digital technology. Current clinical tests are limited in their presentation, and are poor at detecting/measuring stereoacuity in those with limited stereopsis. Given the relevance of the stereoacuity measurement to management choices and functional outcomes, new testing methods would be beneficial to fully assess stereoacuity, both static and dynamic.