Stereopsis, stereotests, and their relation to vision screening and clinical practice

Evaluation of 3D tablet-based stereoacuity test ASTEROID in children with normal and abnormal visual acuity

PURPOSE

To assess the utility of 3D, tablet-based, glasses-free Accurate STEReotest (ASTEROID) in children compared with the Titmus test.

METHODS

Children aged 5-13 years were enrolled in a single-center, nonrandomized, observational comparison study and analyzed by age (5-7 vs 8-13 years) and visual acuity (20/25 or better in both eyes vs abnormal). Each participant underwent both the ASTEROID and Titmus stereoacuity tests. Stereoacuity was defined as fine (≤60 arcsec), moderate (61-200 arcsec), coarse (201-1199 arcsec), or very coarse to nil (≥1200 arcsec). Agreement between the tests was assessed using a weighted kappa (κ) statistic based on all four categories.

RESULTS

A total of 112 children were included: 28 aged 5-7 with normal visual acuity, 30 aged 5-7 with abnormal visual acuity, 34 aged 8-13 with normal visual acuity, and 20 aged 8-13 with abnormal visual acuity. Mean ASTEROID score was 688 ± 533 arcsec (range, 13-1200 arcsec). Agreement between ASTEROID and Titmus test scores for participants overall was moderate (κ = 0.52). By subgroup, agreement was fair for children 5-7 with abnormal visual acuity (κ = 0.31), moderate for children 5-7 with normal visual acuity (κ = 0.47) and children 8-13 with normal visual acuity (κ = 0.42), and substantial for children 8-13 with abnormal visual acuity (κ = 0.76). Where ASTEROID and Titmus score group varied, ASTEROID score was poorer in 94% (47/50) of cases.

CONCLUSIONS

ASTEROID is a digital, tablet-based test that evaluates global stereopsis, does not require glasses, and provides a continuum of scores. Among children, ASTEROID has good agreement with the Titmus test; however, it may be more sensitive at detecting stereovision deficits. Further study is necessary to determine which test is more accurate.

Binocular Visual Function Changes After Corneal Collagen Cross-linking in Patients With Keratoconus

PURPOSE

High-order aberrations (HOAs) have been demonstrated to profoundly affect both visual acuity and stereoacuity in patients with keratoconus. Corneal collagen cross-linking (CXL) has been proven to significantly lower HOAs in keratoconus. Yet, to the present date, no evaluation of the effect of the procedure on stereopsis has been performed. The purpose of the study was to assess differences in binocular visual performance in patients with keratoconus before and after CXL.

METHODS

Patients with keratoconus undergoing standard Dresden protocol epi-off CXL in the ophthalmology department of Policlinico Universitario Agostino Gemelli Hospital received slitlamp examination, uncorrected distance visual acuity and corrected distance visual acuity assessment, corneal tomography, Lang stereotest, TNO stereoacuity assessment, distance and near cover test, and Irvine test before surgery and 6 months after CXL. Stereopsis tests were performed with spectacle correction.

RESULTS

The analysis included 30 patients (mean age 24.63 ± 3.49 years). The Lang test improved after treatment ( P 0.027), with 6 of 30 patients (20%) showing a positive Lang test before CXL compared with 16 of 30 patients (53.3%) after treatment. Moreover, TNO stereoacuity increased after treatment ( P 0.043), and 14 of 30 patients (46.7%) manifested an improvement of at least 250″ at the TNO test after CXL. In this subgroup of patients, total root mean square values decreased after treatment ( P < 0.001), whereas patients who did not manifest a clinically significant improvement in stereoacuity did not show a reduction in total root mean square values after CXL ( P = 0.11). The results of cover test and Irvine test did not vary after CXL.

CONCLUSIONS

Patients with keratoconus showing a reduction of HOAs after CXL also manifest a significant improvement in stereoacuity after the treatment.

Differences in stereoacuity between crossed and uncrossed disparities reduce with practice

INTRODUCTION

Stereoacuity, like many forms of hyperacuity, improves with practice. We investigated the effects of repeated measurements over multiple visits on stereoacuity using two commonly utilised clinical stereotests, for both crossed and uncrossed disparity stimuli.

METHODS

Participants were adults with normal binocular vision (n = 17) aged between 18 and 50 years. Stereoacuity was measured using the Randot and TNO stereotests on five separate occasions over a six week period. We utilised both crossed and uncrossed stimuli to separately evaluate stereoacuity in both disparity directions. A subset of the subject group also completed a further five visits over an additional six week period. Threshold stereoacuity was determined by the lowest disparity level at which the subjects could correctly identify both the position and disparity direction (crossed or uncrossed) of the stimulus. Data were analysed by repeated measures analysis of variance.

RESULTS

Stereoacuity for crossed and uncrossed stimuli improved significantly across the first five visits (F1,21  = 4.24, p = 0.05). The main effect of disparity direction on stereoacuity was not significant (F1  = 0.02, p = 0.91). However, a significant interaction between disparity direction and stereotest was identified (F1  = 7.92, p = 0.01).

CONCLUSIONS

Stereoacuity measured with both the TNO and Randot stereotests improved significantly over the course of five repetitions. Although differences between crossed and uncrossed stereoacuity were evident, they depended on the stereotest used and reduced or disappeared after repeated measurements. A single measure of stereoacuity is inadequate for properly evaluating adult stereopsis clinically.

Pattern-Induced Visual Discomfort and Anxiety in Migraineurs: Their Relationship and the Effect of Colour

In migraineurs, coloured lenses were found to reduce the visual stress caused by an aversive pattern known to trigger migraines by 70%, but do such patterns also produce a low-level anxiety/fear response? Is this response lessened by colour? We sought to investigate this in a study comprising a broad screening component followed by a dot-probe experiment to elicit attentional biases (AB) to aversive patterns. Undergraduate psychology students completed headache and visual discomfort (VD) questionnaires (N = 358), thereby forming a subject pool from which 13 migraineurs with high visual discomfort and 13 no-headache controls with low visual discomfort, matched on age and sex, completed a dot-probe experiment. Paired stimuli were presented for 500 ms: aversive achromatic 3 cpd square wave gratings vs control, scrambled patterns. These conditions were repeated using the colour that was most comfortable for each participant. VD was greater in the more severe headache groups. On all measures, the migraineurs were more anxious than the controls, and a positive relationship was found between VD and trait anxiety. The 3 cpd gratings elicited an aversive AB in the migraine group which was somewhat reduced by the use of colour, and this was not seen in the controls. The results suggest a new role for colour in reducing visual stress via anxiety/fear reduction.

Exploring the effects of degraded vision on sensorimotor performance

PURPOSE

Many people experience unilateral degraded vision, usually owing to a developmental or age-related disorder. There are unresolved questions regarding the extent to which such unilateral visual deficits impact on sensorimotor performance; an important issue as sensorimotor limitations can constrain quality of life by restricting 'activities of daily living'. Examination of the relationship between visual deficit and sensorimotor performance is essential for determining the functional implications of ophthalmic conditions. This study attempts to explore the effect of unilaterally degraded vision on sensorimotor performance.

METHODS

In Experiment 1 we simulated visual deficits in 30 participants using unilateral and bilateral Bangerter filters to explore whether motor performance was affected in water pouring, peg placing, and aiming tasks. Experiment 2 (n = 74) tested the hypothesis that kinematic measures are associated with visuomotor deficits by measuring the impact of small visual sensitivity decrements created by monocular viewing on sensorimotor interactions with targets presented on a planar surface in aiming, tracking and steering tasks.

RESULTS

In Experiment 1, the filters caused decreased task performance-confirming that unilateral (and bilateral) visual loss has functional implications. In Experiment 2, kinematic measures were affected by monocular viewing in two of three tasks requiring rapid online visual feedback (aiming and steering).

CONCLUSIONS

Unilateral visual loss has a measurable impact on sensorimotor performance. The benefits of binocular vision may be particularly important for some groups (e.g. older adults) where an inability to complete sensorimotor tasks may necessitate assisted living. There is an urgent need to develop rigorous kinematic approaches to the quantification of the functional impact of unilaterally degraded vision and of the benefits associated with treatments for unilateral ophthalmic conditions to enable informed decisions around treatment.

Associations Between Binocular Depth Perception and Performance Gains in Laparoscopic Skill Acquisition

The ability to perceive differences in depth is important in many daily life situations. It is also of relevance in laparoscopic surgical procedures that require the extrapolation of three-dimensional visual information from two-dimensional planar images. Besides visual-motor coordination, laparoscopic skills and binocular depth perception are demanding visual tasks for which learning is important. This study explored potential relations between binocular depth perception and individual variations in performance gains during laparoscopic skill acquisition in medical students naïve of such procedures. Individual differences in perceptual learning of binocular depth discrimination when performing a random dot stereogram (RDS) task were measured as variations in the slope changes of the logistic disparity psychometric curves from the first to the last blocks of the experiment. The results showed that not only did the individuals differ in their depth discrimination; the extent with which this performance changed across blocks also differed substantially between individuals. Of note, individual differences in perceptual learning of depth discrimination are associated with performance gains from laparoscopic skill training, both with respect to movement speed and an efficiency score that considered both speed and precision. These results indicate that learning-related benefits for enhancing demanding visual processes are, in part, shared between these two tasks. Future studies that include a broader selection of task-varying monocular and binocular cues as well as visual-motor coordination are needed to further investigate potential mechanistic relations between depth perceptual learning and laparoscopic skill acquisition. A deeper understanding of these mechanisms would be important for applied research that aims at designing behavioral interventions for enhancing technology-assisted laparoscopic skills.

Binocular Vision and Stereopsis Across the Animal Kingdom

Most animals have at least some binocular overlap, i.e., a region of space that is viewed by both eyes. This reduces the overall visual field and raises the problem of combining two views of the world, seen from different vantage points, into a coherent whole. However, binocular vision also offers many potential advantages, including increased ability to see around obstacles and increased contrast sensitivity. One particularly interesting use for binocular vision is comparing information from both eyes to derive information about depth. There are many different ways in which this might be done, but in this review, I refer to them all under the general heading of stereopsis. This review examines the different possible uses of binocular vision and stereopsis and compares what is currently known about the neural basis of stereopsis in different taxa. Studying different animals helps us break free of preconceptions stemming from the way that stereopsis operates in human vision and provides new insights into the different possible forms of stereopsis. Expected final online publication date for the Annual Review of Vision Science, Volume 7 is September 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Role of improved distance and near visual acuity with low vision aids to enhance stereopsis in retinal diseases

Purpose:

The purpose of this study was to examine role of improved distance and near best-corrected visual acuity (DBCVA and NBCVA) with use of magnification devices to enhance stereopsis in low vision (LV) subjects having retinal diseases.

Methods:

In a cross-sectional observational study without control, 84 subjects having LV due to retinal diseases were examined for an improvement of BCVA with use of magnifying low vision aids (LVAs) (2X for DBCVA and 3X for NBCVA). The stereopsis scores on titmus fly test were recorded with near refractive correction “on” and then with 3X magnification. The improvement in stereopsis for distance was however estimated through statistical correlation values.

Results:

The DBCVA (P < 0.001), NBCVA (P < 0.001) and stereopsis (P < 0.001) improved statistically significantly (SS) following magnifying LVA. There was no correlation between pre-LVA stereopsis and pre-LVA DBCVA (r = 0.059; P = 0.444;NSS) and post-LVA DBCVA (r = 0.054; P = 0.487;NSS); and no correlation between post-LVA stereopsis and pre-LVA DBCVA (r = 0.042; P = 0.592;NSS) and post-LVA DBCVA (r = 0.08; P = 0.920;NSS). There was no correlation between pre-LVA stereopsis and pre-LVA NBCVA (r = 0.044; P = 0.572;NSS) and no correlation between post-LVA stereopsis and pre-LVA NBCVA (r = 0.108; P = 0.165;NSS). But positive correlation between pre-LVA stereopsis and post-LVA NBCVA (r = 0.347; P < 0.001) and between post-LVA stereopsis and post-LVA NBCVA (r = 0.445; P < 0.001) was SS.

Conclusion:

The use of magnification as LVA improves both the BCVA and stereopsis. The increase in DBCVA with LVA improves the stereopsis for distance though it may not be SS while improvement in NBCVA with LVA enhances stereopsis for near objects in SS manner.

Reduced macular thickness and macular vessel density in early-treated adult patients with PKU

Purpose

Macular structure is poorly evaluated in early-treated phenylketonuria (ETPKU). To evaluate potential changes, we aimed to examine retinas of PKU patients using optical coherence tomography (OCT) with additional OCT angiography (OCTA) and compare the results to healthy controls.

Methods

A total of 100 adults were recruited in this monocentric, case-control study: 50 patients with ETPKU (mean age: 30.66 ± 8.00 years) and 50 healthy controls (mean age: 30.45 ± 7.18 years). Macular thickness, vessel density and flow area of the right eye was assessed with spectral domain OCT angiography SD-OCT(A). Macular microstructural data between the ETPKU and control group was compared. In the ETPKU group, the relationship between visual functional parameters (best corrected visual acuity [VA], spherical equivalent [SE], contrast sensitivity [CS] and near stereoacuity) and microstructural alterations was examined. The dependency of OCT(A) values on serum phenylalanine (Phe) level was analysed.

Results

There was significant average parafoveal and perifoveal total retinal layer thinning in ETPKU patients compared to healthy controls (p < 0.016 and p < 0.001, respectively), while the foveal region remained unchanged in the ETPKU group. Whole macular and parafoveal superficial capillary plexus density was significantly decreased in ETPKU compared to controls (p < 0.001). There were no significant differences in the foveal avascular zone, nonflow area, macular superficial and deep capillary plexus between the groups. The temporal parafoveal inner retinal layer thickness was found to negatively correlate with individual Phe levels (r = -0.35, p = 0.042). There was no difference in vascular density and retinal thickness in the subgroup analysis of patients with good therapy adherence compared to patients on a relaxed diet.

Conclusions

Durable elevation in Phe levels are only partially associated with macular retinal structural changes. However, therapy adherence might not influence these ophthalmological complications.

Clinical Usefulness of a Computerized Vision Chart for Distance Stereoacuity Assessment in Children with Intermittent Exotropia

INTRODUCTION

The aim of this study is to evaluate distance stereoacuity in children with intermittent exotropia (IXT) using a computerized vision chart (CVC), to compare the results to the normal subjects, and to determine if any correlation between stereoacuity and IXT severity exits.

METHODS

A prospective case-control study was conducted including 24 children with IXT and 25 age-matched normal subjects. The mean age was 8.9 ± 4.5 in IXT group and 9.4 ± 4.2 in control group. The majority of patients (n = 17) had basic type IXT. Full ophthalmic examinations, deviations and stereoacuity tests were evaluated. Stereoacuity was measured with the CVC for distance stereoacuity and Randot stereotest book for near stereoacuity. Level of fusional control in patients with IXT was assessed using Newcastle Control Score (NCS). Seven of the patients with IXT were also reevaluated postoperatively.

RESULTS

Near stereoacuity was good in both IXT and control groups, and there was no significant difference between groups. There was a poor correlation between near stereoacuity and NCS (r_s = 0.15, p = .48). Distance stereoacuity in the IXT group was significantly reduced compared to controls (p = .004). There was a positive correlation between distance stereoacuity values and NCS in patients with IXT (r_s = 0.73, p < .001).

CONCLUSION

Diminished distance stereoacuity in children with IXT can be detected with the CVC and this test may be useful for deciding the timing of surgical intervention and postoperative evaluation.

Unimpaired perception of relative depth from perspective cues in strabismus

Strabismus is a relatively common ophthalmological condition where the coordination of eye muscles to binocularly fixate a single point in space is impaired. This leads to deficits in vision and particularly in three-dimensional (3D) space perception. The exact nature of the deficits in 3D perception is poorly understood as much of understanding has relied on anecdotal reports or conjecture. Here, we investigated, for the first time, the perception of relative depth comparing strabismic and typically developed binocular observers. Specifically, we assessed the susceptibility to the depth cue of perspective convergence as well as the capacity to use this cue to make accurate judgements of relative depth. Susceptibility was measured by examining a 3D bias in making two-dimensional (2D) interval equidistance judgements and accuracy was measured by examining 3D interval equidistance judgements. We tested both monocular and binocular viewing of images of perspective scenes under two different psychophysical methods: two-alternative forced-choice (2AFC) and the method of adjustment. The biasing effect of perspective information on the 2D judgements (3D cue susceptibility) was highly significant and comparable for both subject groups in both the psychophysical tasks (all ps < 0.001) with no statistically significant difference found between the two groups. Both groups showed an underestimation in the 3D task with no significant difference between the group's judgements in the 2AFC task, but a small statistically significant difference (ratio difference of approx. 10%, p = 0.016) in the method of adjustment task. A small but significant effect of viewing condition (monocular versus binocular) was revealed only in the non-strabismic group (ratio difference of approx. 6%, p = 0.002). Our results show that both the automatic susceptibility to, and accuracy in the use of, the perspective convergence cue in strabismus is largely comparable to that found in typically developed binocular vision, and have implications on the nature of the encoding of depth in the human visual system.

Altered visual functions, macular ganglion cell and papillary retinal nerve fiber layer thickness in early-treated adult PKU patients

Purpose

Retinal changes are poorly described in early treated phenylketonuria (ETPKU). We aimed to investigate possible visual functional and ocular microstructural changes in adult patients with ETPKU. Optical coherence tomography (OCT) and its angiography (OCTA) data from patients with PKU were compared to healthy controls.

Methods

In this prospective, monocentric, cross-sectional, case-control study 50 patients with ETPKU and 50 healthy subjects were evaluated with OCT and OCTA. Measurements were performed on right eyes. The following visual function parameters were studied: best corrected visual acuity (BCVA), spherical equivalent (SE), contrast sensitivity and near stereoacuity; microstructural parameters: retinal nerve fiber layer thickness (RNFLT), ganglion cell layer (GCC) thickness, focal loss of volume (FLV), global loss of volume (GLV), peripapillary, papillary vessel density (VD), ocular axial length (AL) and intraocular pressure (IOP).

Results

Among functional tests there were significant differences in contrast sensitivity at 1.5 (p < 0.001), 6 (p < 0.013), 12 (p < 0.001), 18 (p < 0.003) cycles per degree, in near stereoacuity (Titmus Wirt circles, p < 0.001) and in best corrected visual acuity (BCVA, p < 0.001). A statistically significant, moderate positive linear correlation was observed between BCVA and average Phe levels over the last ten years (β = 0.49, p < 0.001). The average (p < 0.001), superior (p < 0.001) inferior GCC (p < 0.001), the FLV (p < 0.003), GLV (p < 0.001) and the average RNFLT (p < 0.004) values of the PKU group were significantly lower than the controls. The serum phenylalanine level (Phe) in the PKU group negatively correlated with inferior (−0.32, p < 0.007), superior (r = −0.26, p < 0.028) and average (−0.29 p < 0.014) RNFL and with AL (−0.32, p < 0.026). In AL we detected a significant difference (p < 0.04) between the good and suboptimal dietary controlled group. There was no significant difference between the ETPKU and control group in the measured vessel density parameters and in IOP.

Conclusions

Our results suggest that functional and ocular microstructural defects are present in patients with PKU, and some of them may depend on dietary control. The mechanism is unclear, but the correlation indicates the importance of strict dietary control in terms of preservation of retinal functions.

Development of stereo vision in young infants

In this study, infants' visual processing of depth-inducing stimuli was tested using a new method suitable for experimental settings. Stereograms of the Lang-Stereopad^® were presented in a timed preferential-looking paradigm to determine infants' preference for a stereogram as compared to a stimulus not inducing an impression of depth. A total of 80 infants were tested at 7 months of age; of these, a sub-sample of 41 infants were tested longitudinally at 4 and 7 months to characterize the developmental trajectory of their preference. Infants were simultaneously presented with a card showing a random-dot stereogram (800" disparity) and a similar looking dummy card without stereogram. In the total sample, 7-month-olds showed a clear preference for the stereogram regardless of sex. In the longitudinal sample, 7-month-olds but not 4-month-olds looked significantly longer to the stereogram as compared to the dummy card. On individual level, 56% of the 4-month-olds and 85% of the 7-month-olds predominantly looked at the stereogram. The findings yield evidence for a clear developmental progression and show that the test cards of the Lang-Stereopad^® prototype provide a viable instrument to determine the preference for depth-inducing stimuli in young infants when used in a controlled experimental setting.

Correlations between clinical measures and symptoms: Report 1: Stereoacuity with accommodative, vergence measures, and symptoms

AIM

The aim of this study was to explore associations between reduced stereoacuity and clinical measures of accommodation, vergences, and symptoms which could facilitate the development of quick and reliable screening tools.

METHODS

Using a multi-stage random cluster sampling, 1211 high school students (481 males and 730 females) between 13 and 18 years of age, were selected and examined. Visual acuity, stereoacuity and suppression, refractive errors, near point of convergence, heterophoria and fusional vergences, as well as, amplitude of accommodation, accommodative response, facility and relative accommodation were evaluated. Correlations among variables and the validity of Randot stereoacuity to distinguish between children with and without defective clinical measures as well as symptomatic versus asymptomatic children were characterized by the sensitivity and specificity of the tests.

RESULTS

The overall mean stereoacuity was 43.9 ± 25.23 s arc, and 18.9% [95% Confidence Interval, 16.6-21.4%)] of the participants had reduced stereoacuity (defined as ≥60). Stereoacuity values and symptoms scores were worse in children with defective clinical measures. The Receiver Operation Curve showed that maximum sensitivity and specificity was obtained with near point of convergence break (≥10 cm) of (0.70 95% confidence interval: 0.63-0.77) with Randot stereoacuity test (defined as ≥60 s arc). The correlations between reduced stereoacuity and symptoms scores was moderately strong and statistically significant (Pearson's, r = 0.507, p = 0.01). The Receiver Operation Curve showed that maximum sensitivity and specificity obtained with the Convergence Insufficiency Symptoms Survey was 0.57 (95% Confidence interval = 0.53-0.62, p = 0.001), sensitivity of 90.26%, and specificity 15.26% with the Randot stereoacuity test.

CONCLUSION

Reduced stereoacuity, defective clinical measures and symptoms of asthenopia were prevalent among sample of school children studied. Randot stereoacuity test could fairly distinguish between defective and normal clinical measures; though the accuracy to differentiate between symptomatic and asymptomatic school children is poor. These findings highlight the need for validation of a simple and fast screening tool in school settings. Further studies to confirm above findings will be needed.

The tolerance of anisometropia

PURPOSE

This study examines aniseikonia, Aniseikonia tolerance range (ATR), anisometropia and patient-reported outcomes (PRO) in an anisometropic population compared with a non-anisometropic population. The relationship between anisometropia and aniseikonia is determined, and the correlations between aniseikonia, anisometropia and ATR versus PRO are described.

METHODS

One hundred and twenty-three patients with IOL-induced anisometropia ≥1 dioptre (D) (the anisometropic group) and 17 patients who had IOL-induced anisometropia <1 D (the control group) were included. Best corrected visual acuity, aniseikonia, ATR and stereoacuity were examined, and two questionnaires were completed: convergence insufficiency symptom survey (CISS) and Visual Function Questionnaire (VFQ-39).

RESULTS

One hundred and thirteen patients had anisometropia >1 and <3 D, and 10 patients had anisometropia >3 D. There was no difference in PRO between the control group and the anisometropic group (Mann-Whitney, p-values VFQ: 0.96, CISS: 0.06). There was no correlation between anisometropia and PRO (Spearman's rank correlation test p-values: VFQ: 0.54, CISS: 0.57). Patients with low ATR were more sensitive towards anisometropia and had lower PRO than patients with high ATR (Mann-Whitney, p-values: VFQ: 0.0008, CISS: 0.11). A large tolerance of aniseikonia was observed.

CONCLUSION

No correlation between PRO and anisometropia or aniseikonia was found. Patients with low ATR are at risk of visual complaints if they are exposed to IOL-induced anisometropia. ATR might be a future screening tool in cataract patients.

Comparison of a New, Filter-Free Stereopsis Test (BEST) With the Randot Stereotest in a Pediatric Cohort

PURPOSE

To evaluate the Bernell Evaluation of Stereopsis Test (BEST) (Bernell Corporation, Mishawaka, IN), a new lenticular technology and filter-free test to measure stereopsis in children, and compare it to the Randot Stereotest (Randot) (Stereo Optical, Inc., Chicago, IL).

METHODS

This was a retrospective review of the medical records of children examined at the Center for Pediatric Ophthalmology at Hadassah-Hebrew University Medical Center from July to November 2018. All children were evaluated with the Randot and BEST in a random order.

RESULTS

The study included 100 children (53% female, 64% orthophoric) with a mean age of 8.52 ± 3.18 years (range: 3.3 to 17.8 years) and mean best corrected visual acuity of 0.178 ± 0.16 logMAR (range: 0 to 0.7 logMAR). The mean BEST stereoacuity was 1.772 ± 0.27 log seconds of arc (arcsec), whereas the mean Randot stereo-acuity was 1.778 ± 0.39 log arcsec (P = .835). The Bland- Altman analysis revealed an overall bias of 0.0073 log arcsec (95% confidence interval: 0.04219 to 0.05679 log arcsec), with limits of agreement of -0.4816 to 0.4962 log arcsec (0.3299 to 3.1347 arcsec). A significant proportional bias was noted because the difference between the tests was significantly larger in higher log arcsec values (t = 5.566, P < .001). Age, gender, strabismus, and visual acuity did not affect the differences between the stereoacuity tests (P > .05). Both tests were influenced by strabismus but not monocular amblyopia.

CONCLUSIONS

BEST stereoacuity measurements were comparable to those of the Randot, with no significant difference in crude values, minimal bias, and narrow limits of agreement. A larger, clinically insignificant variability between tests was noted with lower stereoacuity values, because children achieved better scores with the BEST. The BEST may be a valuable tool in the arsenal of the ophthalmologist. [J Pediatr Ophthalmol Strabismus. 2020;57(2):129-135.].

Assessment of stereo acuity levels using random dot stereo acuity chart in college students

Background and Aims:

Watching 3D images are known to induce more ocular, systemic fatigue and discomfort, which can be referred to as '3D asthenopia', than watching two-dimensional (2D) images. This study was designed to determine the stereo acuity levels among college students and compare it with the hours of use of digital technology.

Methods:

University students in the age group of 18-25 years were screened for visual acuity for distance and near. Refraction was done to find the presence of refractive errors. Those students who had no vergence or accommodation dysfunction and orthophoria were only included in the study. Stereopsis was assessed using random dot stereo acuity chart. The stereo acuity results were grouped as either normal (20 arc seconds or better), Borderline (25 arc seconds to 40 arc seconds) and reduced stereopsis (50 arc seconds to 400 arc seconds). Students were also questioned about the hours of use of digital media.

Results:

The average age of the 246 participates was 20 ± 1.9 years with 78 (32%) were males and 168 (68%) were females. 7% of the population was found to be myopic in our study. The hours of use of digital technology ranged from 0-9 hours a day. Only 13.1% of the student's population met the normal level of stereopsis (20 arc seconds). Around 44.3% of the study population was found to have borderline stereopsis. Also 42.6% of the study population, reduced stereopsis was found. Among the reduced stereo acuity levels, we found stereoacuity levels as low as 100-200 arc seconds were found in nearly 17.6% of the study population.

Conclusion:

It is very much evident from this study that a large group of college students are not enjoying the highest level of binocular vision, which in turn can have a negative impact on their academic performance.

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.

Using stereoscopic visualizations as templates to construct a spatial hands-on representation-is there a novelty effect?

Sculpting representations of human organs out of modeling clay is an acknowledged method of teaching anatomical structures. Because of its potential to provide detailed spatial information, stereoscopic imagery can be understood to function as a suitable template for such sculpting tasks. Currently, it is unknown whether the advantages of stereoscopic images for modeling structures result from enhanced depth impression alone, or whether task performance is impacted by factors such as situational intrinsic motivation and perceived competence while sculpting a human organ using stereoscopic imagery as template. To clarify these queries, 35 eighth-grade students constructed a representation of the nasal cavity consisting of modeling clay. After the working phase, their situational intrinsic motivation and their perceived competence were assessed by a paper-and-pencil test and then analyzed, as was the elaboration of the sculpted representations. A control group with 38 students working with nonstereoscopic visualizations functioned as a counterpart. Stereoscopic imagery outperformed nonstereoscopic imagery concerning the accuracy in elaborating structures within the representations. However, there was no difference between situational intrinsic motivation and perceived competence in the context of using the digital template for forming the representations. Within the cohort working with nonstereoscopic imagery, situational intrinsic motivation was correlated with task performance. In contrast, within the cohort working with stereoscopic imagery, there was no relation concerning this. The findings show that depth impression due to stereoscopic imagery can be utilized to construct template-close representations, independently of situational feelings. This independence from situational sensitivities indicates that low situational intrinsic motivation will not condemn students to poor task performance.

Which Stereotest do You Use? A Survey Research Study in the British Isles, the United States and Canada

A wide range of stereotests are available to measure stereopsis. Because each test has its own advantages and disadvantages, opinions differ on which is the preferred test to use in clinical practice. We conducted surveys comparing the use of stereotests in the British Isles and in the United States and Canada.

Two online surveys were developed following consultation with eye care professionals, one for each geographical area. Both surveys included two questions on the frequency of use of different stereotests, two questions on best practice stereotests, and two questions on the usefulness of stereotests. Researchers made distinctions between appointments with children below or above 6 years old for respondents from the British Isles and below or above 5 years old for respondents from the Unites Stated and Canada. The surveys were distributed through professional organisations.

We found Frisby to be the most used stereotest on the British Isles for both age groups. In the US and Canada, Titmus and Randot stereotest are more frequently used. Respondents consider these tests as the best practice stereotests. Eye care professionals agree stereotests are useful in the diagnosis and treatment decision making and even more so in obtaining an accurate measure of stereoacuity, especially with older children.

The effects of experimentally induced graded monocular and binocular astigmatism on near stereoacuity

Purpose

To determine the effects of experimentally induced graded monocular and binocular astigmatism on near Stereoacuity in healthy adults.

Method

This prospective cross-sectional study was performed on 60 healthy adults ranging between 19 and 33 years of age recruited from College of Applied Medical Sciences. All subjects were emmetropic with normal binocular single vision, and stereoacuity of 40 sec of arc. Enrolled subjects were divided into four groups, each with 15 participants. Myopic astigmatism was induced in two groups, either monocularly or binocularly using +1.00 DC and +2.00 DC at different axes 45, 90 and 180. The remaining two groups were subjected to induced hypermetropic astigmatism using −1.00 DC and −2.00 DC at different axes 45, 90 and 180. The Titmus Fly Stereo Test was used to measure near stereoacuity both before and after induction of astigmatism.

Results

There was a reduction in stereoacuity with an increase in dioptric power of astigmatism (p < 0.05). In all groups, oblique astigmatism had the most significant effect followed by against the rule astigmatism and then with the rule astigmatism. Binocular induced hypermetropic astigmatism caused more reduction in stereoacuity than binocular induced myopic astigmatism, but statistically not significant. A similar impact was noted between monocular myopic astigmatism and monocular hyperopic astigmatism (p = 0.037), (p = 0.049) and (p = 0.044) with 2.00 D cylinder at 180, 90 and 45 axes, respectively.

Conclusion

The results indicate that the small amount of monocular or binocular astigmatism will affect on Stereoacuity, and the amount of reduction varies according to the axis of orientation.

Depth perception in patients with congenital color vision deficiency

PURPOSE

To assess the effect of type and severity of congenital color vision deficiency (CCVD) on depth perception.

METHODS

Thirty-one male patients with a known diagnosis of CCVD were included in the study group and 31 age-matched healthy subjects in the control group. After standard ophthalmological examination including best corrected visual acuity (BCVA) testing with Snellen chart, slit-lamp examination, non-contact tonometry, and fundus examination, all patients underwent color perception testing with Hardy-Rand-Rittler (HRR) 4th edition pseudoisochromatic test plates and stereoacuity testing with Titmus stereo test plates.

RESULTS

Of the 31 patients with CCVD, 7 were protanope and 24 were deuteranope. Mean stereoacuity was 46.77 ± 11.3, 105.7 ± 69.0, and 134.1 ± 115.2 in the control, protanope, and deuteranope groups, respectively. Stereoacuity was significantly better in the control group than in the protanope and deuteranope groups (p = 0.039, p < 0.001 respectively). No significant difference was observed between protanopes and deuteranopes regarding stereoacuity (p = 0.73). Mean BCVA was -0.01 ± 0.03, -0.02 ± 0.07, and -0.10 ± 0.11 in the control, protanope, and deuteranope groups, respectively. Mean BCVA in deuteranopes was significantly better than the control group (p = 0.004), while mean BCVA in deuteranopes and protanopes did not differ significantly (p = 0.056). No significant difference was observed between the control group and protanopes regarding visual acuity (p = 0.921).

CONCLUSIONS

Our study showed that color vision had an important effect on depth perception and CCVD may cause decreased stereoacuity.

A review of vision screening methods for children

Background: What constitutes an appropriate vision screening protocol is controversial, because the tests or methods are expected to be cost-effective, expedient and easy but efficient in detecting visual anomalies among children.Aim: This review intends to compare the different vision screening tests for children and methods in the interest of identifying the most effective screening method from the standpoint of validity, public acceptance, expediency and cost.Method: The literature search was performed for this review using the Medline, Science Direct and EBSCOhost databases. The search terms used were vision screening methods or tests, children’s vision screenings, computer software programs and vision screening instruments. The inclusion criteria for the articles reviewed were all types of articles related to vision screening methods. The exclusion criteria were all articles for which full text was not available and those not available in English. Eighty articles were analysed, of which 33 were found to have complied with the inclusion criteria and were selected. From the first round of articles retrieved, additional references were identified by a manual search among the cited references.Results: Evidence from the literature reviewed demonstrated that the conventional vision screening method (isolated and combination tests) is the method commonly used to detect a range of relevant visual anomalies among the schoolgoing age group (≥ 6 years) and drew attention to the need for training of vision screening personnel. However, in addition to the conventional method, other vision screening methods include instruments as an adjunct for screening preschoolers and those difficult to screen (≤ 6 years).Conclusion: Inconsistencies in what constitutes an appropriate vision screening method still exist, especially with the booming market of using computer software programs, which still needs to be validated.

A comparison of tests for quantifying sensory eye dominance

Clinicians rely heavily on stereoacuity to measure binocular visual function, but stereo-vision represents only one aspect of binocularity. Lab-based tests of sensory eye dominance (SED) are commonplace, but have not been translated to wider clinical practice. Here we compare several methods of quantifying SED in a format suitable for clinical use. We tested 30 participants with ostensibly normal vision on eight tests. Seven tests (#1-7) were designed to quantify SED in the form of an interocular balance-point (BP). In tests #1-6, we estimated a contrast-BP, the interocular difference in contrast required for observers to be equally likely to base their judgement on either eye, whereas in test #7 we measured binocular rivalry (interocular ratio of sensory dominance duration). We compare test-retest reliability (intra-observer consistency) and test-validity (inter-observer discriminatory power) and compare BP to stereoacuity (test #8). The test that best preserved inter-observer differences in contrast balance while maintaining good test-retest reliability was a polarity judgement using superimposed opposite-contrast polarity same-identity optotypes. A reliable and valid measure of SED can be obtained rapidly (20 trials) using a simple contrast-polarity judgement. Tests that use polarity-rivalrous stimuli elicit more reliable judgments than those that do not. SIGNIFICANCE STATEMENT: Although sensory eye dominance is central to understanding normal and disordered binocular vision, there is currently no consensus as to the best way to measure it. Here we compare several candidate measures of sensory eye dominance and conclude that a reliable measure of SED can be achieved rapidly using a judgement of stimulus contrast-polarity.

Stereoscopic Vision in Macular Telangiectasia Type 2

PURPOSE

To investigate stereoscopic vision in patients with macular telangiectasia (MacTel) type 2 and correlate paracentral sensitivity loss to reduced stereoscopic function.

METHODS

In a prospective single-center study, 50 patients with MacTel type 2 and 25 age-matched controls were investigated. Stereoscopic function was evaluated with Lang I, Titmus, and TNO tests. Sensitivity of the central 16° was tested using fundus-controlled perimetry (microperimetry). Functional loss was quantified as depth, size, and localization of scotomata.

RESULTS

Both the Titmus and the TNO test revealed significantly reduced stereoscopic vision in patients compared to controls (p < 0.0001 for both). This applied even to patients with only relative or monocular paracentral scotoma. A strong correlation was observed for reduced stereoscopic vision with horizontal scotoma size and with the distance of scotomata from the foveal center.

CONCLUSIONS

The results indicate that stereoscopic vision is impaired early in patients with MacTel type 2. A paracentral sensitivity loss, even if mild and limited to one eye, may considerably interfere with stereoscopic function despite normal visual acuity. Projection of paracentral scotomata within the patient's central visual field plays an important role in stereoscopic vision and should be considered when interpreting stereoscopic test results.

Monocular Ghost Image Offset Thresholds: Dependent on Target Size and Ghost Image Relative Brightness

SIGNIFICANCE

This is the first report of monocular ghost image offset thresholds measured using O optotypes. Monocular diplopia is a complaint of patients and is the result of a variety of etiologies. Furthermore, monocular image doubling also can be a confounding variable of vectographic stereoacuity tests, warranting an investigation of ghost image offset thresholds.

PURPOSE

To measure ghost image offset thresholds of normal observers and how they are affected by offset orientation, target size, and ghost image relative luminance.

METHODS

Participants were five individuals without ocular abnormalities aged 21 to 32 years. Stimuli were viewed monocularly and consisted of Sloan "O" optotypes generated on a computer monitor with varying levels of image doubling. Ghost image offset thresholds were determined using a spatial 2-alternative forced-choice paradigm and probit analysis of the frequency of seeing data.

RESULTS

Under close-to-optimal conditions, monocular ghost image offset thresholds ranged between 14 and 22 arc seconds, a level that might be considered a hyperacuity. Ghost image offset detection thresholds demonstrated a U-shaped relationship with optotype size, with optimum thresholds occurring for optotypes sizes of approximately -0.15 logarithmic minimum angle of resolution. There was no measurable effect of offset orientation on ghost image offset detection thresholds. Monocular ghost image offset detection thresholds decreased as ghost image relative luminance increased.

CONCLUSIONS

Ghost image offset detection thresholds can be quite low even when viewing under monocular conditions and relatively low ghost image relative luminance. This should be considered when designing and interpreting the results of vectographic stereoacuity tests.

The impact of stereoscopic imagery and motion on anatomical structure recognition and visual attention performance

Gross anatomy is located in a three-dimensional space. Visualizing aspects of structures in gross anatomy education should aim to provide information that best resembles their original spatial proportions. Stereoscopic three-dimensional imagery might offer possibilities to implement this aim, though some research has revealed potential impairments that may result from observing stereoscopic visualizations, such as discomfort. However, possible impairments of working memory such as decreased visual attention performance due to applying this technology in gross anatomy education have not yet been investigated. Similarly, in gross anatomy education the impact of stereoscopic imagery on learners' recognition of anatomical-spatial relationships and the impact of different presentation formats have only been investigated in a small number of studies. In this study, the performance of 171 teacher trainees working on the anatomy of hearing was examined, either with non-stereoscopic or stereoscopic imagery. Static and dynamic picture presentations were applied. Overall, benefits for stereoscopic imagery on estimating anatomical-spatial relations were found. The performance on a visual attention test indicates that the impact of stereoscopic visualizations on the human cognitive system varies more from person to person compared to non-stereoscopic visualizations. In addition, combinations of temporarily moving pictures and stereoscopic imagery lead to decreased visual attention performance compared to combinations of moving pictures and non-stereoscopic imagery. Anat Sci Educ 11: 15-24. © 2017 American Association of Anatomists.

Normative Values for Near and Distance Clinical Tests of Stereoacuity

PURPOSE

Extensive literature exists on normative stereoacuity values for younger children, but there is less information about normative stereoacuity in older children/adults. Individual stereotests cannot be used interchangeably-knowing the upper limit of normality for each test is important. This report details normative stereoacuity values for 5 near/distance stereotests drawn from a large sample of participants aged 16-40 years, across 3 studies.

METHODS

Participants (n=206, mean age 22.18±5.31 years) were administered the following stereotests: TNO, Preschool Randot, Frisby, Distance Randot, and Frisby-Davis 2. Medians and upper limits were calculated for each test.

RESULTS

Upper limits for each stereotest were as follows: TNO (n=127, upper limit=120" arc), Preschool Randot (PSR, n=206, upper limit=70" arc), Frisby (n=206, upper limit=40" arc), Distance Randot (n=127, upper limit=160" arc), and Frisby-Davis 2 (n=109, upper limit=25" arc).

CONCLUSIONS

Normative values for each stereotest are identified and discussed with respect to other studies. Potential sources of variation between tests, within testing distances, are also discussed.

Video Game Vision Syndrome: A New Clinical Picture in Children?

PURPOSE

To examine a possible relationship between exposure to video games/electronic screens and visual issues in children between 3 and 10 years of age.

METHODS

An observational, cross-sectional study of a population of children using video games was employed. All patients between 3 and 10 years of age were recruited at an outpatient unit accredited by the Italian Regional Health Service. Three hundred twenty children (159 boys and 161 girls; mean age = 6.9 ± 2 years) were observed. Ophthalmological examination included assessment of stereoscopic vision on Lang-Stereotests I and II (LANG-STEREOTEST AG, Küsnacht, Switzerland) and identification of the dominant eye using the Dolman method. Furthermore, a questionnaire was used to record asthenopic symptoms and daily exposure to video games and electronic screens. Two groups of children were examined according to the average amount of time spent playing video games daily: children who played video games for less than 30 minutes per day and not every day (control group) and children who played video games for 30 minutes or more every day (video game group). Both groups were then divided into two subgroups: children using other types of electronic screens (eg, televisions, computers, tablets, and smartphones) for less than 3 hours daily (low electronic use subgroup) and children using other types of electronic screens for 3 hours or more per day (high electronic use subgroup).

RESULTS

Asthenopia (especially headache, eyelid tic, transient diplopia, and dizziness), absence of fine stereopsis, and refractive errors were statistically more frequent (mainly in the dominant eye) in children in the video game group.

CONCLUSIONS

These symptoms were frequent and peculiar in the video game group and might be part of a video game vision syndrome that has not been defined yet. It is important to recognize these signs as possible functional disorders to avoid erroneous diagnostic and therapeutic interventions. [J Pediatr Ophthalmol Strabismus. 2017;54(6):346-355.].

Overestimation of stereo thresholds by the TNO stereotest is not due to global stereopsis

PURPOSE

It has been repeatedly shown that the TNO stereotest overestimates stereo threshold compared to other clinical stereotests. In the current study, we test whether this overestimation can be attributed to a distinction between 'global' (or 'cyclopean') and 'local' (feature or contour-based) stereopsis.

METHODS

We compared stereo thresholds of a global (TNO) and a local clinical stereotest (Randot Circles). In addition, a global and a local psychophysical stereotest were added to the design. One hundred and forty-nine children between 4 and 16 years old were included in the study.

RESULTS

Stereo threshold estimates with TNO were a factor of two higher than with any of the other stereotests. No significant differences were found between the other tests. Bland-Altman analyses also indicated low agreement between TNO and the other stereotests, especially for higher stereo threshold estimates. Simulations indicated that the TNO test protocol and test disparities can account for part of this effect.

DISCUSSION

The results indicate that the global - local distinction is an unlikely explanation for the overestimated thresholds of TNO. Test protocol and disparities are one contributing factor. Potential additional factors include the nature of the task (TNO requires depth discrimination rather than detection) and the use of anaglyph red/green 3D glasses rather than polarizing filters, which may reduce binocular fusion.

Community Involvement and Benefits From an International Service Learning Program

Service learning (SL) is a form of experiential learning in which students are involved in community service activities that are related to academic course objectives. A key aspect that separates SL from other forms of experiential learning is the mutually beneficial nature of the service activities. Much of the SL and international SL (ISL) literature has focused on positive learning outcomes for students, with much less focus on the benefits of SL to the community. Speech, Language, and Hearing Services (SLHS) in Zambia is an intensive SL short-term study abroad program. This paper describes the benefits to the community via the SLHS in Zambia program.

A Single Mechanism Can Account for Human Perception of Depth in Mixed Correlation Random Dot Stereograms

In order to extract retinal disparity from a visual scene, the brain must match corresponding points in the left and right retinae. This computationally demanding task is known as the stereo correspondence problem. The initial stage of the solution to the correspondence problem is generally thought to consist of a correlation-based computation. However, recent work by Doi et al suggests that human observers can see depth in a class of stimuli where the mean binocular correlation is 0 (half-matched random dot stereograms). Half-matched random dot stereograms are made up of an equal number of correlated and anticorrelated dots, and the binocular energy model-a well-known model of V1 binocular complex cells-fails to signal disparity here. This has led to the proposition that a second, match-based computation must be extracting disparity in these stimuli. Here we show that a straightforward modification to the binocular energy model-adding a point output nonlinearity-is by itself sufficient to produce cells that are disparity-tuned to half-matched random dot stereograms. We then show that a simple decision model using this single mechanism can reproduce psychometric functions generated by human observers, including reduced performance to large disparities and rapidly updating dot patterns. The model makes predictions about how performance should change with dot size in half-matched stereograms and temporal alternation in correlation, which we test in human observers. We conclude that a single correlation-based computation, based directly on already-known properties of V1 neurons, can account for the literature on mixed correlation random dot stereograms.

Composition of a vision screen for servicemembers with traumatic brain injury: consensus using a modified nominal group technique

Vision impairment is common in the first year after traumatic brain injury (TBI), including among service members whose brain injuries occurred during deployment in Iraq and Afghanistan. Occupational therapy practitioners provide routine vision screening to inform treatment planning and referral to vision specialists, but existing methods are lacking because many tests were developed for children and do not screen for vision dysfunction typical of TBI. An expert panel was charged with specifying the composition of a vision screening protocol for servicemembers with TBI. A modified nominal group technique fostered discussion and objective determinations of consensus. After considering 29 vision tests, the panel recommended a nine-test vision screening that examines functional performance, self-reported problems, far-near acuity, reading, accommodation, convergence, eye alignment and binocular vision, saccades, pursuits, and visual fields. Research is needed to develop reliable, valid, and clinically feasible vision screening protocols to identify TBI-related vision disorders in adults.

Pitfalls in the Use of Stereoacuity in the Diagnosis of Nonorganic Visual Loss

PURPOSE

The Titmus Stereotest (Stereo Optical Co., Inc., Chicago, IL) has been used to estimate visual acuity (VA) in the evaluation of nonorganic visual loss. Previous predictions were derived from optical degradation of VA in normal subjects and may not account for the variability seen in patients with neuro-ophthalmic pathologies included in the differential diagnosis of nonorganic visual loss. The purpose of this study was to evaluate the relationship between Titmus stereoacuity and minimal VA based on a real-world testing environment.

DESIGN

Cross-sectional observational study.

PARTICIPANTS

All patients treated at the authors' neuro-ophthalmology service between April 25, 2014, and July 31, 2014.

METHODS

All subjects underwent routine neuro-ophthalmic examination, including Titmus stereoacuity measurements. A compound Bayesian logit-lognormal model accounting for heteroscedasticity was used to determine 95% and 99% prediction intervals of the worse eye's near VA based on stereoacuity. Logarithm of the minimum angle of resolution VA and log stereoacuity were analyzed.

MAIN OUTCOME MEASURES

Titmus stereoacuity and worse eye VA.

RESULTS

Of 561 patients, 364 subjects 11 to 91 years of age were included. Titmus stereoacuity was associated positively with VA: 9 circles correct (40 seconds of arc) indicated VA of at least 20/40 with 95% confidence and VA of at least 20/79 with 99% confidence; 6 circles correct (80 seconds of arc) indicated VA of at least 20/62 and 20/180, respectively; and 4 circles correct (140 seconds of arc) indicated VA of at least 20/110 and 20/570, respectively.

CONCLUSIONS

When fully accounting for individual variation and the full spectrum of neuro-ophthalmic diseases affecting VA, stereoacuity remains associated with VA, but previous commonly used VA estimates based on stereoacuity overestimated VA. Our results more accurately predict minimum VA from Titmus stereoacuity and should be used preferentially when evaluating patients with suspected nonorganic visual loss. We demonstrated that Titmus stereoacuity cannot definitively establish normal VA, and therefore can suggest, but not fully establish, the diagnosis of nonorganic visual loss.

Contribution of binocular vision to the performance of complex manipulation tasks in 5-13years old visually-normal children

Individual studies have shown that visuomotor coordination and aspects of binocular vision, such as stereoacuity and dynamic vergence control, continue to improve in normally developing children between birth and early teenage years. However, no study has systematically addressed the relationship between the development of binocular vision and fine manipulation skills. Thus, the aim of this cross-sectional study was to characterize performance of complex manipulation tasks during binocular and monocular viewing. Fifty-two children, between 5 and 13years old, performed 2 manipulation tasks: peg-board and bead-threading under randomized viewing conditions. Results showed that binocular viewing was associated with a significantly greater improvement in performance on the bead-threading task in comparison to the peg-board task and the youngest children showed the greatest decrement in task performance under the monocular viewing condition when performing the bead-threading task. Thus, the role of binocular vision in performance of fine manipulation skills is both task- and age-dependent. These findings have implications for assessment of visuomotor skills in children with abnormal binocular vision, which occurs in 2-3% of otherwise typically developing children.

Effects of Stereoscopic Depth on Vigilance Performance and Cerebral Hemodynamics

OBJECTIVE

We tested the possibility that monitoring a display wherein critical signals for detection were defined by a stereoscopic three-dimensional (3-D) image might be more resistant to the vigilance decrement, and to temporal declines in cerebral blood flow velocity (CBFV), than monitoring a display featuring a customary two-dimensional (2-D) image.

BACKGROUND

Hancock has asserted that vigilance studies typically employ stimuli for detection that do not exemplify those that occur in the natural world. As a result, human performance is suboptimal. From this perspective, tasks that better approximate perception in natural environments should enhance performance efficiency. To test that possibility, we made use of stereopsis, an important means by which observers interact with their everyday surroundings.

METHOD

Observers monitored a circular display in which a vertical line was embedded. Critical signals for detection in a 2-D condition were instances in which the line was rotated clockwise from vertical. In a 3-D condition, critical signals were cases in which the line appeared to move outward toward the observer.

RESULTS

The overall level of signal detection and the stability of detection over time were greater when observers monitored for 3-D changes in target depth compared to 2-D changes in target orientation. However, the 3-D display did not retard the temporal decline in CBFV.

CONCLUSION

These results provide the initial demonstration that 3-D displays can enhance performance in vigilance tasks.

APPLICATION

The use of 3-D displays may be productive in augmenting system reliability when operator vigilance is vital.

The clinical effectiveness and cost-effectiveness of second-eye cataract surgery: a systematic review and economic evaluation

BACKGROUND

Elective cataract surgery is the most commonly performed surgical procedure in the NHS. In bilateral cataracts, the eye with greatest vision impairment from cataract is operated on first. First-eye surgery can improve vision and quality of life. However, it is unclear whether or not cataract surgery on the second eye provides enough incremental benefit to be considered clinically effective and cost-effective.

OBJECTIVE

To conduct a systematic review of clinical effectiveness and analysis of cost-effectiveness of second-eye cataract surgery in England and Wales, based on an economic model informed by systematic reviews of cost-effectiveness and quality of life.

DATA SOURCES

Twelve electronic bibliographic databases, including MEDLINE, EMBASE, Web of Science, The Cochrane Library and the Centre for Reviews and Dissemination databases were searched from database inception to April 2013, with searches updated in July 2013. Reference lists of relevant publications were also checked and experts consulted.

REVIEW METHODS

Two reviewers independently screened references, extracted and checked data from the included studies and appraised their risk of bias. Based on the review of cost-effectiveness, a de novo economic model was developed to estimate the cost-effectiveness of second-eye surgery in bilateral cataract patients. The model is based on changes in quality of life following second-eye surgery and includes post-surgical complications.

RESULTS

Three randomised controlled trials (RCTs) of clinical effectiveness, three studies of cost-effectiveness and 10 studies of health-related quality of life (HRQoL) met the inclusion criteria for the systematic reviews and, where possible, were used to inform the economic analysis. Heterogeneity of studies precluded meta-analyses, and instead data were synthesised narratively. The RCTs assessed visual acuity, contrast sensitivity, stereopsis and several measures of HRQoL. Improvements in binocular visual acuity and contrast sensitivity were small and unlikely to be of clinical significance, but stereopsis was improved to a clinically meaningful extent following second-eye surgery. Studies did not provide evidence that second-eye surgery significantly affected HRQoL, apart from an improvement in the mental health component of HRQoL in one RCT. In the model, second-eye surgery generated 0.68 incremental quality-adjusted life-years with an incremental cost-effectiveness ratio of £1964. Model results were most sensitive to changes in the utility gain associated with second-eye surgery, but otherwise robust to changes in parameter values. The probability that second-eye surgery is cost-effective at willingness-to-pay thresholds of £10,000 and £20,000 is 100%.

LIMITATIONS

Clinical effectiveness studies were all conducted more than 9 years ago. Patients had good vision pre surgery which may not represent all patients eligible for second-eye surgery. For some vision-related patient-reported outcomes and HRQoL measures, thresholds for determining important clinical effects are either unclear or have not been determined.

CONCLUSIONS

Second-eye cataract surgery is generally cost-effective based on the best available data and under most assumptions. However, more up-to-date data are needed. A well-conducted RCT that reflects current populations and enables the estimation of health state utility values would be appropriate. Guidance is required on which vision-related, patient-reported outcomes are suitable for assessing effects of cataract surgery in the NHS and how these measures should be interpreted clinically.

STUDY REGISTRATION

This project is registered as PROSPERO CRD42013004211.

FUNDING

This project was funded by the National Institute for Health Research Health Technology Assessment programme.

Visual performance and the use of colored filters in children who are deaf

PURPOSE

To assess visual performance and the effects of color overlays on reading in children who were deaf and children who could hear.

METHODS

Thirty-one children who were deaf (mean [± SD] age, 14 [± 1.99] years) and 39 children who could hear (mean [± SD] age, 13.58 [± 3.09] years) underwent an optometric examination with specific emphasis on near vision. Participants chose an overlay with color optimal for clarity and comfort and completed the Wilkins Rate of Reading Test both with and without an overlay of this color. Nineteen of the participants who were deaf were retested a year later with a modified rate of reading test that used only words that can readily be signed. This modified rate of reading test was repeated 1 week after its first administration.

RESULTS

Participants who were deaf had greater ametropia (p = 0.003), a more distant near point of convergence (p = 0.002), and reduced amplitude of accommodation (p < 0.001) compared with normal-hearing participants. All the children who were deaf chose a color overlay, with 45% choosing a yellow overlay, which increased the rate of reading by 18%. Only 66% of the participants who could hear chose an overlay, and it had no effect on reading speed. With the modified reading test, 7 of 19 (37%) again chose yellow. These participants showed a 9% increase in reading speed with the yellow overlay, which was repeatable 1 week later. The remainder showed no increase in rate of reading with their chosen overlay.

CONCLUSIONS

An eye examination of children who are deaf needs to include a comprehensive assessment of near visual function so that deficiencies of amplitude of accommodation, near point convergence, and ametropia can be treated. A yellow overlay improved reading speed in the participants who were deaf, whereas other colors did not, a finding at variance with earlier work on hearing populations.

Stereo vision and strabismus

Binocular stereopsis, or stereo vision, is the ability to derive information about how far away objects are, based solely on the relative positions of the object in the two eyes. It depends on both sensory and motor abilities. In this review, I briefly outline some of the neuronal mechanisms supporting stereo vision, and discuss how these are disrupted in strabismus. I explain, in some detail, current methods of assessing stereo vision and their pros and cons. Finally, I review the evidence supporting the clinical importance of such measurements.

Manufacturer changes lead to clinically important differences between two editions of the TNO stereotest

PURPOSE

Stereoacuity tests used in clinical practice should be repeatable and reproducible. However, it has been observed in a clinical setting that new editions of the TNO stereotest appear to give different values from those obtained using previous versions. The purpose of the present research was to investigate this observation.

METHODS

One hundred and twenty-one Dutch subjects, 88 (73%) females and 33 (27%) males, with an average age of 34.0 years (range 18-55) had their stereoacuity measured using two different versions of the TNO stereoacuity test (TNO 13 and TNO 15). The TNO was tested in a counterbalanced order so that consecutive subjects started with alternate editions to avoid bias.

RESULTS

There was a significant difference (p < 0.001) between the median value for stereoacuity measured with TNO 13 (30 s of arc) and TNO 15 (60 s of arc). The bias between the two test versions was -0.23 Log arcseconds (95% limits of the differences: 0.15 to -0.60 Log arcseconds).

CONCLUSION

This study reveals that results obtained with two different editions of a commonplace stereoacuity test are not comparable. New versions come on the market at regular intervals and the assumption that they will give the same results as previous versions may not be valid. Besides the statistically significant difference between the TNO 13 and TNO 15, the Bland-Altman plot also showed a considerable bias and the 95% limits of the differences between the TNO 13 and TNO 15 are more than two steps on the Log arcsecond scale. This difference between two editions of the TNO stereotests is not clinically acceptable and therefore it is inappropriate to use the two versions of the test interchangeably. It is important in both research and clinical records to specify the edition of the TNO test used.

Pointing in stereoscopic space

Movements in virtual stereoscopic space tend to be difficult and slow. To shed some light on the origins of these difficulties, we studied open-loop pointing with targets presented in a mirror stereoscope. Whilst targets were placed in a virtual horizontal plane, movement end-points were located in an inclined plane. The inclination of this plane was a stable individual characteristic. Amplitude errors gave no evidence of a contraction bias. Open-loop movements had fairly straight trajectories, but closed-loop movements were strongly curved so that they ended in a horizontal plane rather than in an inclined one. Effects of closed-loop movements on subsequent open-loop movements (calibration effects) were only small. These findings reveal that movements in a virtual environment exhibit a number of characteristics also seen in real environments, but in addition they reflect specific visual illusions. Extensive calibration procedures are needed to overcome such errors for the reliance on closed-loop control of pointing to be relaxed.

Recovery from virtual environment exposure: expected time course of symptoms and potential readaptation strategies

OBJECTIVE

This study investigated potential means of facilitating a return to normal functioning following virtual environment (VE) exposure using a peg-in-hole exercise in recalibrating hand-eye coordination, a targeted gait movement (rail walking) in recalibrating vestibular (i.e., postural) aftereffects, and natural decay.

BACKGROUND

Despite technology advances and considerable efforts focused on the identification and quantification of VE aftereffects, few have addressed means for recuperation, the focus of the current study.

METHOD

After 15 min-60 min of VE exposure and recalibratory exercises, hand-eye coordination and postural stability were assessed electronically, the former via a 3-D measure capturing pointing errors, and the latter by head and body oscillations while standing in the tandem Romberg position. Both measurements were collected immediately after VE exposure and every 15 min up to 1 hr thereafter.

RESULTS

Participants (more than 900 college students) who experienced the peg-in-hole readaptation strategy had a significant decrease (p < 0.000 in pointing errors following the exercise; the other two methods (i.e., rail walking, natural decay) showed no significant change. For posture, all groups showed significant improvement during the 15 minutes after VE exposure, yet none returned to baseline by 1 hr postexposure.

CONCLUSION

Although hand-eye coordination readaptation strategies showed noticeable effects immediately after they were performed, aftereffects were not completely eliminated after 1 hr; hence further research on readaptation strategies is essential to achieve more substantial recalibratory gains in hand-eye coordination and posture. Additionally, hand-eye coordination and vestibular aftereffects may require a period exceeding the VE immersion time in order to recover.

APPLICATION

These findings may serve as a guide in the development of monitoring policies following VE exposure.

Effects of low stereo acuity on performance, presence and sickness within a virtual environment

To examine the effect of stereo vision on performance, presence and oculomotor disturbances within a virtual environment (VE), two groups of 23 participants (good stereo acuity/low stereo acuity) were evaluated. Groups were matched in terms of gender, age and VE design factors (the latter were accounted for to ensure a similar VE experience between groups). Participants were immersed in a VE maze for up to 1h during which time they interacted with the environment while performing a number of stationary and movement-based tasks. Individuals with low stereo acuity traveled further to complete two tasks in the VE, yet performance time on these tasks was comparable to participants with good stereo acuity. Although participants with impaired stereo vision likely did not fully benefit from a stereoscopic view of the scene, they may have received sufficient depth information from movement-based cues to efficiently accomplish these tasks in a comparable amount of time. Overall performance, based on both the number of tasks completed and the total translational distance moved (based on input device movement) within the VE was not hindered for those with low stereo acuity. In addition, the expected increase in oculomotor disturbances for this group was not evident in this study, and both groups reported comparable amounts of presence from VE exposure. These results suggest that when head tracking is included as part of the VE experience (i.e., motion parallax cues exist), participants with low stereo acuity can be expected to perform comparable to normal sighted individuals, experience a comparable sense of presence, and report no increase in adverse effects when viewing scenes via stereoscopic displays. Thus, motion parallax cues may adequately provide a sense of depth within a VE, and alleviate theorized performance decrements for individuals with low stereo acuity. The results of this study have implications for those designing entertainment simulations or other such applications open to the general public, where people with low stereo acuity may routinely participate.

What to expect from immersive virtual environment exposure: influences of gender, body mass index, and past experience

For those interested in using head-coupled PC-based immersive virtual environment (VE) technology to train, entertain, or inform, it is essential to understand the effects this technology has on its users. This study investigated potential adverse effects, including the sickness associated with exposure and extreme responses (emesis, flashbacks). Participants were exposed to a VE for 15 to 60 min, with either complete or streamlined navigational control and simple or complex scenes, after which time measures of sickness were obtained. More than 80% of participants experienced nausea, oculomotor disturbances, and/or disorientation, with disorientation potentially lasting > 24 hr. Of the participants, 12.9% prematurely ended their exposure because of adverse effects; of these, 9.2% experienced an emetic response, whereas only 1.2% of all participants experienced emesis. The results indicate that designers may be able to reduce these rates by limiting exposure duration and reducing the degrees of freedom of the user's navigational control. Results from gender, body mass, and past experience comparisons indicated it may be possible to identify those who will experience adverse effects attributable to exposure and warn such individuals. Applications for this research include military, entertainment, and any other interactive systems for which designers seek to avoid adverse effects associated with exposure.