Binocular Conditions Research Articles

Monocular and binocular reading performance in subjects with normal binocular vision

BackgroundIt is well known that problems with binocular vision can cause issues for reading; less known is to what extent binocular vision improves reading performance. The purpose of this study was to explore the role of binocularity by directly comparing monocular and binocular reading in subjects with typical reading skills and normal binocular vision. A secondary purpose was to assess any asymmetry in monocular performance and its association with the sighting dominant eye.MethodsIn a balanced repeated measures experiment, 18 subjects read paragraphs of text under monocular and binocular conditions. All subjects went through an optometric examination before inclusion. Reading speed and eye movements were recorded with an eye tracker.ResultsThe mean difference in reading speed (2.1 per cent) between monocular (dominant and non‐dominant eye averaged) and binocular reading speed was not significant. A significant difference in reading speed was found between binocular and the non‐dominant eye, as determined by the far sighting test (p = 0.03). Monocular reading showed significantly increased (8.9 per cent) fixation duration (p < 0.01) and longer regressive saccades by 0.43 character spaces (p < 0.01). Reading with the non‐dominant eye, as determined by the near sighting test, showed increased progressive saccade length by 0.2 characters compared to the dominant eye (p = 0.03). No other significant differences between dominant and non‐dominant eyes were found. The agreement between the faster reading eye and ocular dominance was 44 to 56 per cent depending on whether dominance was determined at near or far.ConclusionThe outcomes suggest that in subjects with normal binocular vision, there is no marked enhancement in reading performance by binocular vision when reading paragraphs of text. Furthermore, the monocular reading performance appears to be close to equal and any small differences in performance appear not to be strongly associated with ocular dominance.

The effects of ageing and visual field loss on pointing to visual targets.

PurposeTo investigate the effect of ageing on visuomotor function and subsequently evaluate the effect of visual field loss on such function in older adults.MethodsTwo experiments were performed: 1) to determine the effect of ageing on visual localisation and subsequent pointing precision, and 2) to determine the effect of visual field loss on these outcome measures. For Experiment 1, we measured visual localisation and pointing precision radially at visual eccentricities of 5, 10 and 15° in 25 older (60–72 years) and 25 younger (20–31 years) adults. In the pointing task, participants were asked to point to a target on a touchscreen at a natural pace that prioritised accuracy of the touch. In Experiment 2, a subset of these tasks were performed at 15° eccentricity under both monocular and binocular conditions, by 8 glaucoma (55–76 years) and 10 approximately age-matched controls (61–72 years).ResultsVisual localisation and pointing precision was unaffected by ageing (p>0.05) and visual field loss (p>0.05), although movement time was increased in glaucoma (p = 0.01).ConclusionVisual localisation and pointing precision to high contrast stimuli within the central 15° of vision are unaffected by ageing. Even in the presence of significant visual field loss, older adults with glaucoma are able perform such tasks with reasonable precision provided the target can be perceived and movement time is not restricted.

Effects of Visual Noise on Binocular Summation in Patients With Strabismus Without Amblyopia

Patients with strabismus often complain of difficulty navigating through visually stimulating environments without clear explanation for this symptom. Binocular summation (BiS), defined as the superiority of binocular over monocular viewing on visual threshold tasks, is decreased in conditions that cause large interocular differences in visual acuity, but is not well studied in strabismic populations without amblyopia. The authors hypothesized that strabismus may lead to decreased BiS for tasks related to discrimination within increased background complexity. The goal of this study was to test the extent of BiS in patients with strabismus during discrimination of a luminance target disk embedded in visual noise. Participants included 10 exotropic, 10 esotropic, and 13 age-matched control patients. Performance of a task detecting a luminance-target was measured at 0, 10, and 20 μdeg(2) of visual noise for binocular and monocular conditions. BiS was calculated as the ratio of binocular contrast sensitivity to monocular contrast sensitivity for the target embedded in noise. Patients with strabismus had lower BiS values than controls, with a significant decrease on linear regression in patients with strabismus at 20 μdeg(2) of noise (P = .05), with a trend toward significance at 10 μdeg(2) of noise (P = .07). Patients with strabismus showed a mean binocular inhibition (summation ratio < 1) at both noise levels. These findings support the hypothesis that strabismus can lead to decreased BiS and even binocular inhibition. Despite literature showing enhanced BiS in visually demanding situations such as high levels of visual noise or low contrast, BiS was not significantly affected by visual noise in either group.

Transient improvements in fixational stability in strabismic amblyopes following bifoveal fixation and reduced interocular suppression

To test the hypothesis that fixational stability of the amblyopic eye in strabismics will improve when viewing provides both bifoveal fixation and reduced inter-ocular suppression by reducing the contrast to the fellow eye. Seven strabismic amblyopes (Age: 29.2 ± 9 years; five esotropes and two exotropes) showing clinical characteristics of central suppression were recruited. Interocular suppression was measured by a global motion task. For each participant, a balance point was determined which defined contrast levels for each eye where binocular combination was optimal (interocular suppression minimal). When the balance point could not be determined, this participant was excluded. Bifoveal fixation was established by ocular alignment using a haploscope. Participants dichoptically viewed similar targets (a cross of 2.3° surrounded by a square of 11.3°) at 40 cm. Target contrasts presented to each eye were either high contrast (100% to both eyes) or balanced contrast (attenuated contrast in the fellow fixing eye). Fixation stability was measured over a 5 min period and quantified using bivariate contour ellipse areas in four different binocular conditions; unaligned/high contrast, unaligned/balance point, aligned/high contrast and aligned/balance point. Fixation stability was also measured in six control subjects (Age: 25.3 ± 4 years). Bifoveal fixation in the strabismics was transient (58.15 ± 15.7 s). Accordingly, fixational stability was analysed over the first 30 s using repeated measures anova. Post hoc analysis revealed that for the amblyopic subjects, the fixational stability of the amblyopic eye was significantly improved in aligned/high contrast (p = 0.01) and aligned/balance point (p < 0.01) conditions. Fixational stability of the fellow fixing eye was not different statistically across conditions. Bivariate contour ellipse areas of the amblyopic and fellow fixing eyes were therefore averaged for each amblyope in the four conditions and compared with normals. This averaged bivariate contour ellipse area was significantly greater (reduced fixational stability, p = 0.04) in amblyopes compared to controls except in the case of aligned and balanced contrast (aligned/balance point, p = 0.19). Fixation stability in the amblyopic eye appears to improve with bifoveal fixation and reduced interocular suppression. However, once initiated, bifoveal fixation is transient with the strabismic eye drifting away from foveal alignment, thereby increasing the angle of strabismus.

Natural Pupil Size and Ocular Aberration under Binocular and Monocular Conditions

Purpose: To investigate how activity of natural pupils under binocular and monocular conditions affect wave front aberrations. Materials and Methods: Eighteen eyes from 18 subjects (mean age 22.3 ± 0.8 years) were included in the study. The undilated pupil diameters under photopic conditions were measured using the FP-10000 (TMI, Japan) infrared pupillometer. Aberrometry measurements were performed using the KR-9000PW (Topcon, Japan) Hartmann- Shack wavefront sensor. Zernike coefficients were recalculated for the diameters of each pupil under binocular and monocular conditions using Schwiegerling’s algorithm. Multiple regression analysis was performed to analyze independent predictors of the change of higher-order aberration for 6.0 mm from the binocular to the monocular condition. The independent variables were the change of pupil diameter from binocular to monocular condition; binocular pupil diameter; total higher-order aberration for 6.0 mm, sphere, and cylinder. Results: Pupil diameter, total, total higher-order, coma-like, and spherical-like aberrations under monocular conditions were significantly greater than the binocular condition (all P<0.01). The multiple regression of analysis of variables showed that the change of total higher order aberration from the binocular to the monocular condition was related to the change of pupil diameter, and the amount of higher-order aberrations for 6.0 mm (P<0.05). Conclusion: The outcomes suggest that increased pupil diameter under monocular conditions produces higher wavefront aberrations than under binocular conditions, resulting in a degradation of retinal image quality. This effect is enhanced in eyes with greater higher order aberrations and pupil diameter

Accommodative response under monocular and binocular conditions as a function of phoria in symptomatic and asymptomatic subjects

BackgroundThe neurological linkage of vergence and accommodation is a factor which can affect accuracy of accommodation, is in turn associated with symptoms of near‐related visual discomfort. The purpose of this study was to compare the accommodative response under monocular and binocular conditions in symptomatic and asymptomatic participants with different near phorias.MethodsSeventy students at Zahedan University of Medical Sciences, Iran (mean age: 21.2 ± 1.7 years; age range: 18 to 25 years) participated. The participants were divided into symptomatic and asymptomatic groups according to the convergence insufficiency symptom survey questionnaire score. The type and magnitude of the near dissociated phoria were determined using the prism neutralised cover test. The accommodative lag was measured by the ‘monocular estimate method’ (MEM) retinoscopy, at first under binocular and then monocular conditions. Testing distance was 40-cm.ResultsThe accommodative lag in exophoric participants was lower under binocular conditions compared to monocular and in esophoric participants greater under binocular than under monocular conditions. The binocular accommodative response (AR) was greatest in participants with high exophoria at near vision and least in participants with esophoria at near vision (p < 0.001; one‐way analysis of variance). The difference between binocular lag and monocular lag was significantly greater in symptomatic participants than in asymptomatic participants in both exophoria (p < 0.001) and esophoria (p = 0.009) (independent samples t‐test).ConclusionThe near binocular accommodative response was related to near heterophoria. Higher levels of vergence accommodation, resulting in differences in lag under monocular and binocular conditions, may be a factor in near point asthenopia.

Six-month-old infants' perception of the hollow face illusion: evidence for a general convexity bias.

Corrow, Granrud, Mathison, and Yonas (2011, Perception, 40, 1376-1383) found evidence that 6-month-old infants perceive the hollow face illusion. In the present study we asked whether 6-month-old infants perceive illusory depth reversal for a nonface object and whether infants' perception of the hollow face illusion is affected by mask orientation inversion. In experiment 1 infants viewed a concave bowl, and their reaches were recorded under monocular and binocular viewing conditions. Infants reached to the bowl as if it were convex significantly more often in the monocular than in the binocular viewing condition. These results suggest that infants perceive illusory depth reversal with a nonface stimulus and that the infant visual system has a bias to perceive objects as convex. Infants in experiment 2 viewed a concave face-like mask in upright and inverted orientations. Infants reached to the display as if it were convex more in the monocular than in the binocular condition; however, mask orientation had no effect on reaching. Previous findings that adults' perception of the hollow face illusion is affected by mask orientation inversion have been interpreted as evidence of stored-knowledge influences on perception. However, we found no evidence of such influences in infants, suggesting that their perception of this illusion may not be affected by stored knowledge, and that perceived depth reversal is not face-specific in infants.

Redundancy gain in binocular rivalry.

A behavioural advantage is found across a wide range of stimuli when two targets are presented in opposite hemifields compared with those targets being presented together in one hemifield, or one target being presented alone. This advantage for responses to multiple targets versus a single target is often termed redundancy gain. Here we report on the findings of two experiments investigating redundancy gain in binocular rivalry. Experiment 1 presented a rival pair in one hemifield with an additional image presented to both eyes in the opposite hemifield. There was a weak effect of this stable image on the perceived dominance of the images within the rival pair. Experiment 2 presented a second rival pair in either the same or opposite hemifield and showed that instances of joint predominance were greater when the two pairs were presented in opposite hemifields than within the same hemifield. Therefore, the findings suggest that redundancy gain may be extended to stimuli presented under binocular rivalry conditions.

Distribution of Attention in Augmented Reality: Comparison between Binocular and Monocular Presentation

SUMMARY This study investigated the distribution of attention to frontal space in augmented reality (AR). We conducted two experiments to compare binocular and monocular observation when an AR image was presented. According to a previous study, when participants observed an AR image in monocular presentation, they perceived the AR image as more distant than in binocular vision. Therefore, we predicted that attention would need to be shifted between the AR image and the background in not the monocular observation but the binocular one. This would enable an observer to distribute his/ her visual attention across a wider space in the monocular observation. In the experiments, participants performed two tasks concurrently to measure the size of the useful field of view (UFOV). One task was letter/ number discrimination in which an AR image was presented in the central field of view (the central task). The other task was luminance change detection in which dots were presented in the peripheral field of view (the peripheral task). Depth difference existed between the AR image and the location of the peripheral task in Experiment 1 but not in Experiment 2. The results of Experiment 1 indicated that the UFOV became wider in the monocular observation than in the binocular observation. In Experiment 2, the size of the UFOV in the monocular observation was equivalent to that in the binocular observation. It becomes difficult for a participant to observe the stimuli on the background in the binocular observation when there is depth difference between the AR image and the background. These results indicate that the monocular presentation in AR is superior to binocular presentation, and even in the best condition for the binocular condition the monocular presentation is equivalent to the binocular presentation in terms of the UFOV.

The separation of monocular and binocular contrast

The contrast asynchrony is a stimulus configuration that illustrates the visual system's separable responses to luminance and luminance contrast information (Shapiro, 2008; Shapiro et al., 2004). When two disks, whose luminances modulate in phase with each other, are each surrounded by a disk, one light and one dark, observers can see both the in-phase brightness signals and the antiphase contrast signals and can separate the two. Here we present the results of experiments in which observers viewed a similar stimulus dichoptically. We report that no asynchrony is perceived when one eye is presented with modulating disks and the other eye is presented with the black and white surround rings, nor is an asynchrony perceived in gradient versions of the contrast asynchrony. We also explore the "window shade illusion" (Shapiro, Charles, & Shear-Heyman, 2005) dichoptically and find that when a modulating disk is presented to one eye and a horizontally split black/white annulus is presented to the other, observers perceive a "shading" motion up and down the disk. This shading can be seen in either direction in the binocular condition, but it is almost always seen as moving towards low contrast in the monocular condition. These findings indicate the presence of separable retinal and cortical networks for contrast processing at different temporal and spatial scales.

Binocular vision enhances a rapidly evolving affordance priming effect: Behavioural and TMS evidence

Extensive research has suggested that simply viewing an object can automatically prime compatible actions for object manipulation, known as affordances. Here we explored the generation of covert motor plans afforded by real objects with precision (‘pinchable’) or whole-hand/power (‘graspable’) grip significance under different types of vision. In Experiment 1, participants viewed real object primes either monocularly or binocularly and responded to orthogonal auditory stimuli by making precision or power grips. Pinchable primes facilitated congruent precision grip responses relative to incongruent power grips, and vice versa for graspable primes, but only in the binocular vision condition. To examine the temporal evolution of the binocular affordance effect, participants in Experiment 2 always viewed the objects binocularly but made no responses, instead receiving a transcranial magnetic stimulation pulse over their primary motor cortex at three different times (150, 300, 450ms) after prime onset. Motor evoked potentials (MEPs) recorded from a pinching muscle were selectively increased when subjects were primed with a pinchable object, whereas MEPs from a muscle associated with power grips were increased when viewing graspable stimuli. This interaction was obtained both 300 and 450ms (but not 150ms) after the visual onset of the prime, characterising for the first time the rapid development of binocular grip-specific affordances predicted by functional accounts of the affordance effect.

Eye rivalry and object rivalry in the intact and split-brain

Both the eye of origin and the images themselves have been found to rival during binocular rivalry. We presented traditional binocular rivalry stimuli (face to one eye, house to the other) and Diaz-Caneja stimuli (half of each image to each eye) centrally to both a split-brain participant and a control group. With traditional rivalry stimuli both the split-brain participant and age-matched controls perceived more coherent percepts (synchronised across the hemifields) than non-synchrony, but our split-brain participant perceived more non-synchrony than our controls. For rival stimuli in the Diaz-Caneja presentation condition, object rivalry gave way to eye rivalry with all participants reporting more non-synchrony than coherent percepts. We have shown that splitting the stimuli across the hemifields between the eyes leads to greater eye than object rivalry, but that when traditional rival stimuli are split as the result of the severed corpus callosum, traditional rivalry persists but to a lesser extent than in the intact brain. These results suggest that communication between the early visual areas is not essential for synchrony in traditional rivalry stimuli, and that other routes for interhemispheric interactions such as subcortical connections may mediate rivalry in a traditional binocular rivalry condition.

Sublinear binocular integration preserves orientation selectivity in mouse visual cortex

Inputs from the two eyes are first combined in simple cells in the primary visual cortex. Consequently, visual cortical neurons need to have the flexibility to encode visual features under both monocular and binocular situations. Here we show that binocular orientation selectivity of mouse simple cells is nearly identical to monocular orientation selectivity in both anesthetized and awake conditions. In vivo whole-cell recordings reveal that the binocular integration of membrane potential responses is sublinear. The sublinear integration keeps binocularly-evoked depolarizations below threshold at non-preferred orientations, thus preserving orientation selectivity. Computational simulations based on measured synaptic conductances indicate that inhibition promotes sublinear binocular integration, which are further confirmed by experiments using genetic and pharmacological manipulations. Our findings therefore reveal a cellular mechanism for how visual system can switch effortlessly between monocular and binocular conditions. The same mechanism may apply to other sensory systems that also integrate multiple channels of inputs.

The Optokinetic Uncover Test

We devised the optokinetic uncover test to examine the role of peripheral retinal motion input in generating horizontal optokinetic responses in patients with infantile strabismus. To ascertain whether subcortical visual input contributes to the asymmetrical monocular optokinetic responses that characterize infantile esotropia. Observational study in an academic research setting. Ten patients with infantile esotropia. Optokinetic uncover test. Optokinetic testing was performed in 7 patients with isolated infantile esotropia (5 untreated and 2 previously treated) and in 3 patients with infantile esotropia syndrome associated with mild neurological disease. RESULTS All patients showed poor temporally directed optokinetic responses that instantaneously improved when the occluded esodeviated eye was uncovered, exposing it to nasally directed optokinetic motion. This improvement in optokinetic responses did not necessitate a fixation shift to the contralateral eye. Nasally directed optokinetic input to the esodeviated eye can supplement temporal monocular optokinetic responses in the fixating eye under binocular conditions. This nonfoveal optokinetic contribution suggests that monocular nasotemporal optokinetic asymmetry is partly attributable to subcortical visuovestibular responses mediated by nonfoveal retina.

Association between vision impairment and driving exposure in older adults aged 70 years and over: a population‐based examination

To examine the relationship between vision impairment and driving exposure (amount of driving one does) in a population-based sample of older drivers and to examine to what extent cognitive status impacts this relationship. Enrollees consisted of a population-based sample of older adults from Alabama who were ≥70 years old, held a current driver's license, and had driven within the last 3 months. Three aspects of visual function were measured under binocular conditions - habitual distance visual acuity, contrast sensitivity and visual processing speed. General cognitive status was assessed with the mini-mental status examination. Driving exposure was estimated by the Driving Habits Questionnaire that asked about the number of miles, places, trips and days driven per week. Drivers with impaired contrast sensitivity exhibited reduced annual mileage, and a decreased number of places and trips driven per week compared to those with normal contrast sensitivity, even after adjustment for other factors. Slowed visual processing speed was associated with reduced number of days driven per week after adjustment. Visual acuity deficit was not associated with changes in driving exposure. Cognitive status did not impact any of the associations between vision impairment and driving exposure. Older drivers with contrast sensitivity impairment exhibit reduced driving exposure in terms of number of trips and places they drive per week, as well as decreased annual mileage. These apparent self-regulatory practices should be viewed as adaptive because contrast sensitivity impairment elevates motor vehicle collision (MVC) risk and reduction in driving exposure can reduce MVC risk.

Advantages in exploring a new environment with the left eye in lizards

Lizards (Podarcis muralis) preferentially use the left eye during spatial exploration in a binocular condition. Here we allowed 44 adult wild lizards to explore an unknown maze for 20min under a temporary monocular condition whilst recording their movements, particularly the direction of turns made whilst walking within the maze. Lizards with a patch on their right eye, i.e. using their left eye to monitor the environment, moved faster than lizards with a patch on their left eye when turning both leftward and rightward in a T-cross. Hence, right eye-patched lizards were faster than left eye-patched lizards also in turning right, although their right eye was covered. Thus, lizards that could use the left eye/right hemisphere to attend spatial cues appeared to have more control and to be more prompt in exploring the maze. In addition, female lizards with their left eye covered stopped very frequently when they reached crosses, showing a high level of indecision. Results confirm that P. muralis lizards using their left eye only in exploring a new environment react faster and more efficiently than those using the right eye only in exploration. Hence lateralisation of spatial stimuli mediated by the left eye/right hemisphere could provide an advantage to this species.

Test–retest reproducibility of accommodation measurements gathered in an unselected sample of UK primary school children

PurposeTo determine the test–retest reproducibility of accommodation measurements gathered in an unselected sample of primary school children.MethodsMonocular and binocular amplitudes of accommodation (AA) were collected by five different Testers using...

Blobs versus bars: Psychophysical evidence supports two types of orientation response in human color vision

The classic hypothesis of Livingstone and Hubel (1984, 1987) proposed two types of color pathways in primate visual cortex based on recordings from single cells: a segregated, modular pathway that signals color but provides little information about shape or form and a second pathway that signals color differences and so defines forms without the need to specify their colors. A major problem has been to reconcile this neurophysiological hypothesis with the behavioral data. A wealth of psychophysical studies has demonstrated that color vision has orientation-tuned responses and little impairment on form related tasks, but these have not revealed any direct evidence for nonoriented mechanisms. Here we use a psychophysical method of subthreshold summation across orthogonal orientations for isoluminant red-green gratings in monocular and dichoptic viewing conditions to differentiate between nonoriented and orientation-tuned responses to color contrast. We reveal nonoriented color responses at low spatial frequencies (0.25-0.375 c/deg) under monocular conditions changing to orientation-tuned responses at higher spatial frequencies (1.5 c/deg) and under binocular conditions. We suggest that two distinct pathways coexist in color vision at the behavioral level, revealed at different spatial scales: one is isotropic, monocular, and best equipped for the representation of surface color, and the other is orientation-tuned, binocular, and selective for shape and form. This advances our understanding of the organization of the neural pathways involved in human color vision and provides a strong link between neurophysiological and behavioral data.

Replicating and Extending Bourdon's (1902) Experiment on Motion Parallax

Bourdon conducted the first laboratory experiment on observer-produced motion parallax as a cue to depth. In three experiments, we replicated and extended Bourdon's experiment. In experiment 1, we reproduced his finding: when the two cues, motion parallax and relative height, were combined, accuracy of depth perception was high, and when the two cues were in conflict, accuracy was lower. In experiment 2, the relative height cue was replaced with relative retinal image size. As in experiment 1, when the two cues (motion parallax and relative retinal image size) were combined, accuracy was high, but when they were in conflict, it was lower. In experiment 3, the stimuli from experiments 1 and 2 were viewed monocularly with head movement and binocularly without head movement. In the binocular conditions, accuracy, certainty, and the extent of perceived depth were higher than in the monocular condition. In the conflict conditions, accuracy, certainty, and the extent of perceived depth were lower than in the no-conflict condition, but the extent of perceived motion was larger. These results are discussed in terms of recent findings about the effectiveness of motion parallax as a cue for depth.

Quality of Vision with Spectacles, Special Silicone Hydrogel and Gas Permeable Contact Lenses in Keratoconic Patients

ABSTRACT Purpose To evaluate optical quality and visual function in keratoconus patients corrected with RGP contact lenses and a novel special design of silicone hydrogel contact lens. Materials and methods Twelve eyes of six patients with keratoconus were enrolled to experience a new soft contact lens (Soft-K) for keratoconus made of a silicone-hydrogel material and the outcomes were compared to the performance with gas permeable lenses and spectacles. The three situations were compared for monocular and binocular high (100%) and low contrast (10%) ETDRS LogMAR visual acuity and contrast sensitivity function (CSF). Results On average, there was an improvement of more than two lines in visual acuity over spectacle correction and this is statistically significant for both gas permeable (GP) and Soft-K lens (p &lt; 0.001). Visual acuity was not significantly different between GP and Soft-K lens for high contrast acuity but was slightly higher with GP lens for low contrast under binocular conditions. Monocular CSF showed a marked improvement with the Soft-K lens and GP, compared to spectacles correction, particularly for medium and high frequencies; conversely. Conclusion Soft-K silicone hydrogel soft contact lens produces a clinical and statistically significant improvement in visual acuity and contrast sensitivity function over spectacle correction. How to cite this article González-Méijome JM, Peixoto-de- Matos SC, Queiros A, Jorge JM, Diaz-Rey A. Quality of Vision with Spectacles, Special Silicone Hydrogel and Gas Permeable Contact Lenses in Keratoconic Patients. Int J Kerat Ect Cor Dis 2013;2(2):56-59.