Development Of Binocular Vision Research Articles

Harnessing brain plasticity to improve binocular vision in amblyopia: An evidence-based update.

Amblyopia is a developmental visual disorder resulting from atypical binocular experience in early childhood that leads to abnormal visual cortex development and vision impairment. Recovery from amblyopia requires significant visual cortex neuroplasticity, i.e. the ability of the central nervous system and its synaptic connections to adapt their structure and function. There is a high level of neuroplasticity in early development and, historically, neuroplastic responses to changes in visual experience were thought to be restricted to a "critical period" in early life. However, as our review now shows, the evidence is growing that plasticity of the adult visual system can also be harnessed to improve vision in amblyopia. Amblyopia treatment involves correcting refractive error to ensure clear and equal retinal image formation in both eyes, then, if necessary, promoting the use of the amblyopic eye by hindering or reducing visual input from the better eye through patching or pharmacologic therapy. Early treatment in children can lead to visual acuity gains and the development of binocular vision in some cases; however, many children do not respond to treatment, and many adults with amblyopia have historically been untreated or undertreated. Here we review the current evidence on how dichoptic training can be used as a novel binocular therapeutic approach to facilitate visual processing of input from the amblyopic eye and can simultaneously engage both eyes in a training task that requires binocular integration. It is a novel and promising treatment for amblyopia in both children and adults.

Особливості зміни фонової енцефалограми у відповідь на функціональні навантаження у хворих на дисбінокулярну амбліопію залежно від фіксації амбліопічного ока

Background: Analysis of electroencephalogram (EEG) visual-evoked potentials (VEPs) is important for assessing the general integrity of the visual pathway. Pathology in any portion of the visual pathway causes changes in VEP. Percentages of alpha, beta, delta and theta rhythms in the EEG record, frequencies and amplitudes of these waves, and the level of alpha-rhythm suppression are essential for characterizing the state of the visual system. Purpose: To indentify the features of the state of the visual system and changes in the background EEG in response to activation procedures in strabismic amblyopes depending on type of fixation in the amblyopic eye. Material and Methods: Fifty-two strabismic amblyopic patients aged 5-8 years and 15 healthy children of the same age underwent an examination. Of the amblyopic children, 32 had unilateral amblyopia with esotropia (6-15 degrees). Of these 32 children, 20 had eccentric fixation and 12 children, central fixation. The 10–20 system of electrode placement was employed to perform EEG in all children. Rhythms of the background EEG, interhemispheric asymmetry and alpha, theta and delta wave percentages were assessed. Brain potentials were recorded using standard activation procedures to activate deep brain structures. Results: Alpha rhythm was not discernable in the background EEG in the occipital areas in 3.0 ± 2.6 % of cases, and the alpha index was below the normal range in 48.6 ± 8.2 % of patients with a visual acuity worse than 0.3. Delta index was above the normal range (25%-45%) in 48.6 ± 8.2 %, and theta index was above the normal range (with a mean value of 48.4 ± 8.2 %) in 48.6 ± 8.2 % of children. Reduced percentage of alpha activity was found in almost half of strabismic amblyopic children, indicating immaturity of the synchronizing system and impaired oculomotor tuning in the eyes of these children. Abnormal bilateral EEG response to eye-opening stimulation and abnormal bilateral EEG rhythmic driving response (RDR) were seen in most children with eccentric fixation, but not in most children with central fixation. Photic stimulation in strabismic amblyopic children resulted in bilaterally asymmetrical and synchronous theta and delta waves in symmetric frontal (theta and delta percent time of 46.0 ± 8.4%) and occipital (theta and delta percent time of 50.0 ± 8.4%) responses. Conclusion: Increased theta and delta wave percentages in frontal and occipital derivations were found in strabysmic amblyopes (irrespective of type of fixation in the amblyopic eye) compared to healthy controls. Abnormal EEG response to eye opening and abnormal EEG RDR were found in strabysmic amblyopes. This indicates the presence of functional changes in the midline brain structures including the corpus callosum, which impedes the development of binocular vision in strabismic amblyopes.

Novel variants identified in a three‑generation family with concomitant exotropia

Concomitant exotropia is a condition where there is a misalignment between both eyes, which is more prevalent in Asians than in Caucasians. It is an eye disease related to the neural development of binocular vision and eye movement control. Studies have indicated that genetic factors contribute to the development of concomitant exotropia; however, the underlying mutations have not been thoroughly investigated to date. In the present study, whole-exome sequencing was performed in a three-generation family with concomitant exotropia. In the proband and the proband's father, bioinformatics analyses identified a duplication of the genomic region spanning genes PCDHA1-7 and a heterozygous mutation c.3775G>A (p.A1259T) of the COL3A1 gene, which is located in the conserved COLFI domain and leads to decreased stability of the encoded protein product. Furthermore, a deletion of amino acid S165 in the gene NCOA7 was discovered in the family members, including the proband, the proband's mother and maternal grandfather. S165 was predicted to be a conserved phosphokinase site of CK1/VRK and CK1/CK1. The genes in which these variants reside are all involved in cortical neuronal development. The present study reveals novel variants of concomitant exotropia and suggests that aberrant cortical neuronal development may contribute to the origin of concomitant strabismus.

Binocular visual experience drives the maturation of response variability and reliability in the visual cortex

SummaryA fundamental challenge of neuroscience is to understand how a single neuron responds to multiple synaptic inputs effectively and reliably. In primary visual cortex, repeated stimuli to one eye elicit neuronal responses of inherent variability and reliability. However, it remains unclear how this monocular variability and reliability contribute to the establishment of effective and reliable binocular responses and what drives this development. In this study, using in vivo multichannel extracellular recordings, we demonstrate binocular responses in adult mouse visual cortex exhibit low variability and high reliability. This response characteristic is immature during the critical period of binocular vision development. In amblyopic mice, the maturation of binocular variability and reliability is disrupted, and this defect can be partially rescued by enhancing cortical plasticity via dark exposure. In conclusion, the development of cortical response variability and reliability depends on the normal binocular visual experience, which is further regulated by cortical plasticity.

Результаты комплексного лечения обскурационной амблиопии у детей после экстракции врожденной катаракты

Purpose. To evaluate the dynamics of obscuration amblyopia complex treatment in children after congenital cataract lens extraction. Material and methods. We analyzed the case histories of 107 patients from the period of 2016 to 2020, who were diagnosed with congenital cataract, aged 3 to 14 years. There were 84 children (78.5%) with unilateral cataracts who underwent the surgery, and 23 children (21.5%) with bilateral cataracts. All patients were divided into two groups. The first group (main group) included 56 patients (69 eyes) with congenital cataracts, who underwent intraocular lens implantation with repeated pleopto-orthoptic treatment in the postoperative period. The average age was 4.68±2.91 years. Control group included 51 patients (61 eyes) with congenital cataracts who underwent phacoemulsification of congenital cataracts with implantation of an intraocular lens without pleopto-orthoptic treatment in the postoperative period. The average age was 4.81±2.79 years. Results. By the end of the follow-up period, an increase in visual acuity to 0.2 and higher in patients of the main group was noted in 73.9% of cases (51 eyes), in the control group – in 44.3% of cases (27 eyes) (p<0.05). As a result of treatment, central fixation was restored in 38% of patients in the main group, in 20% of patients in the control group (p<0.05). Binocular near vision was developed in 34% of patients in the main group, in 18% of patients in the control group (p<0.05). Conclusion. Complex treatment, including regular pleoptoorthoptic treatment in combination with optical correction, direct occlusion after congenital cataract extraction, demonstrated positive clinical results, which was expressed in an increase of visual acuity, restoration of central fixation, and the development of binocular vision. Key words: obscuration amblyopia, congenital cataract, pleopto-orthoptic treatment, visual functions

Evaluating visuomotor coordination in children with amblyopia.

Past research has reported deficits on reaching and grasping tasks in adults with amblyopia and degraded stereoacuity, but less is known about visuomotor deficits in children-specifically, for complex tasks that require movement sequencing. This study therefore compared the visuomotor performance in 21 children with abnormal binocular vision (patient group) due to amblyopia and/or strabismus to that of 236 children with normal binocular vision development (control group) ages 5-14 years. Visual acuity, stereoacuity, and hand-movement kinematics on a bead-threading task were assessed. The patient group showed significantly longer durations than the control group on grasp, thread, and total movement durations. Both groups of participants were then split into immature (ages 5-9 years) and mature (ages 10-14 years) groups based on the maturation age for these parameters in control children. Grasp duration was longer in both mature and immature patient groups; thread and total movement durations were longer in the mature patient group only. Grasp duration was the most disrupted kinematic parameter in children with disrupted binocular vision due to amblyopia and/or strabismus, regardless of age. The level of stereoacuity loss rather than the depth of visual acuity loss was associated with the severity of visuomotor deficits.

Percentile curves of stereacuity in a Spanish paediatric population

ObjectiveThe main objective of this study was to obtain percentile curves of stereoacuity in arc seconds for a Spanish population aged between three and twelve years of age. Materials and methodsA descriptive, observational and transversal study was conducted, which included children aged between three and twelve years of age who did not present with any known ocular and/or systemic diseases. The convenience sampling method was used to select the sample from three schools and one hospital in the Community of Madrid. The Bueno-Matilla Vision Unit's random dot test was used to measure stereoacuity. A descriptive statistic was performed with the stereoacuity values that were obtained for the 5th, 10th, 25th, 50th, 75th, 90th and 95th percentiles. ResultsThe stereoacuity values of 1300 children were analysed. In the 50th percentile curve, it was determined that stereoacuity values close to 40 sec/arc were present from four years of age, and at four years and nine months, stereoacuity values close to 28 sec/arc were already being observed within said percentile, with values that were similar to those expected in the adult population. A progressive increase was observed, reaching 19 sec/arc before six years of age, with this stereoacuity value becoming more established in children from seven years of age. ConclusionAlthough given the specific type of sampling that was performed it was not possible to generalise the results to the entire population, these percentile curves may aid paediatric professionals in their assessment of the development of this visual ability, which is indicative of the degree of development of binocular vision.

The development of active binocular vision under normal and alternate rearing conditions.

The development of binocular vision is an active learning process comprising the development of disparity tuned neurons in visual cortex and the establishment of precise vergence control of the eyes. We present a computational model for the learning and self-calibration of active binocular vision based on the Active Efficient Coding framework, an extension of classic efficient coding ideas to active perception. Under normal rearing conditions with naturalistic input, the model develops disparity tuned neurons and precise vergence control, allowing it to correctly interpret random dot stereograms. Under altered rearing conditions modeled after neurophysiological experiments, the model qualitatively reproduces key experimental findings on changes in binocularity and disparity tuning. Furthermore, the model makes testable predictions regarding how altered rearing conditions impede the learning of precise vergence control. Finally, the model predicts a surprising new effect that impaired vergence control affects the statistics of orientation tuning in visual cortical neurons.

Distorted optical input affects human perception

Collinear facilitation, the mechanism for grouping contour elements, is a process involving lateral interactions that improve the detectability of a target by the presence of collinear flankers. It was shown that the development of collinear facilitation is experience dependent and that it may be impaired when the visual input is distorted in one meridian (meridional amblyopia). In oblique astigmatism, the blurring is on the opposite oblique meridian in both eyes, resulting in two conflicting images, which may affect the development of binocular vision. We hypothesized that the collinear facilitation of adults with oblique astigmatism is reminiscent of the abnormal development of the lateral facilitation of meridional amblyopia. We explored the perception of binocular vision and collinear facilitation in cases of both distorted and non-distorted vision. Fully corrected participants that tested for the target contrast detection of Gabor patches and two collinear flankers, presented for 80 ms, were positioned at different orientations (0° (180°), 45°, 90°, and 135°) and for different eyes (monocular, binocular). The results show a significant anisotropy for monocular collinear facilitation between the blured and the clear meridians, being lower in the blurriest meridian than in the clearest meridian, resembling the meridional amblyopia results. Collinear facilitation results in poor binocular summation between the monocular channels. Our results indicate that the perceptual behavior was similar to that of meridional amblyopic subjects having an anisotropy of collinear facilitation between cardinal meridians in oblique astigmatic subjects.

Abundance, Diversity, and Distribution of Primates at Welel Mountain, Kellem Wollega Zone, Oromia Region, Ethiopia.

Primates are the mammals of the order Primate that is characterized by advanced development of binocular vision and enlargement of the cerebral hemispheres. The aim of this study was to investigate the abundance, diversity, and distribution of primates on Welel Mountain. From August 2017 to February 2018, we collected data from different parts of Welel Mountain during wet and dry seasons of the year and analyzed them using SPSS version 20. We identified four primate species: Chlorocebus aethiops, Cercopithecus mitis, Papio anubis, and Colobus guereza. We conducted t-test analysis for abundance and distribution of primates in wet and dry season of the year, and the P value obtained was 0.20. The mean percentages of primates in forest, woodland, and shrubs were 43.16%, 32.26%, and 24.58%, respectively. Shannon-Wiener diversity index (H′) value was higher in wet season than in dry season. The current study showed that the species are distributed more evenly in wet season than in dry season, and the number of young individuals is more than that of adults. This indicates that currently the status of primates population on Welel Mountain is good. Therefore, to keep the status of primates in the study area effective, wildlife management and conservation policy should be formulated.

Active efficient coding explains the development of binocular vision and its failure in amblyopia

The development of vision during the first months of life is an active process that comprises the learning of appropriate neural representations and the learning of accurate eye movements. While it has long been suspected that the two learning processes are coupled, there is still no widely accepted theoretical framework describing this joint development. Here, we propose a computational model of the development of active binocular vision to fill this gap. The model is based on a formulation of the active efficient coding theory, which proposes that eye movements as well as stimulus encoding are jointly adapted to maximize the overall coding efficiency. Under healthy conditions, the model self-calibrates to perform accurate vergence and accommodation eye movements. It exploits disparity cues to deduce the direction of defocus, which leads to coordinated vergence and accommodation responses. In a simulated anisometropic case, where the refraction power of the two eyes differs, an amblyopia-like state develops in which the foveal region of one eye is suppressed due to inputs from the other eye. After correcting for refractive errors, the model can only reach healthy performance levels if receptive fields are still plastic, in line with findings on a critical period for binocular vision development. Overall, our model offers a unifying conceptual framework for understanding the development of binocular vision.

Resident Perspectives

Resident Perspectives

Neuroanatomical Structures in Human Extraocular Muscles and Their Potential Implication in the Development of Oculomotor Disorders.

The potential role of sensory feedback from human extraocular muscles has been subjected to considerable speculation in the ophthalmic literature. Extraocular muscles pull against a fairly even load and do not initiate a stretch reflex, even when the eyes are directed toward the boundaries of their respective field of action. These unique working conditions and physiological properties have led to the notion that the sensory signal arising from receptors in extraocular muscles differs from the conventional proprioceptive signal arising from their somatic counterparts. The interest in the receptors at the myotendinous junction of human extraocular muscles has been renewed due to their alleged role in the development of binocular vision and their potential implication in the etiology of binocular vision anomalies. The idea that extraocular muscles provide knowledge of eye position and whether this function can be affected by surgical intervention has initiated several clinical and neuroanatomical studies. Many of these studies support this concept and suggest that surgical procedures that impose only minimal interference with the proprioceptive signal will give a better postoperative result. However, other studies contradict this view because the afferent capacity of the receptors can be questioned and some uncertainties remain. The purpose of this study was to review the related literature and discuss the possible role of ocular proprioceptors in relation to binocular vision and the development of eye motility disorders. [J Pediatr Ophthalmol Strabismus. 2018;55(1):14-22.].

Environmental Enrichment Rescues Binocular Matching of Orientation Preference in the Mouse Visual Cortex.

Neural circuits are shaped by experience during critical periods of development. Sensory deprivation during these periods permanently compromises an organism's ability to perceive the outside world. In the mouse visual system, normal visual experience during a critical period in early life drives the matching of individual cortical neurons' orientation preferences through the two eyes, likely a key step in the development of binocular vision. Here, in mice of both sexes, we show that the binocular matching process is completely blocked by monocular deprivation spanning the entire critical period. We then show that 3 weeks of environmental enrichment (EE), a paradigm of enhanced sensory, motor, and cognitive stimulation, is sufficient to rescue binocular matching to the level seen in unmanipulated mice. In contrast, 6 weeks of conventional housing only resulted in a partial rescue. Finally, we use two-photon calcium imaging to track the matching process chronically in individual cells during EE-induced rescue. We find that for cells that are clearly dominated by one of the two eyes, the input representing the weaker eye changes its orientation preference to align with that of the dominant eye. These results thus reveal ocular dominance as a key driver of the binocular matching process, and suggest a model whereby the dominant input instructs the development of the weaker input. Such a mechanism may operate in the development of other systems that need to integrate inputs from multiple sources to generate normal neuronal functions.SIGNIFICANCE STATEMENT Critical periods are developmental windows of opportunity that ensure the proper wiring of neural circuits, as well as windows of vulnerability when abnormal experience could cause lasting damage to the developing brain. In the visual system, critical period plasticity drives the establishment of binocularly matched orientation preferences in cortical neurons. Here, we show that binocular matching is completely blocked by monocular deprivation during the critical period. Moreover, environmental enrichment can fully rescue the disrupted matching, whereas conventional housing of twice the duration results in a partial rescue. We then use two-photon calcium imaging to track individual cells chronically during the EE-induced recovery, and reveal important insights into how appropriate function can be restored to the nervous system after the critical period.

High AC/A Ratio Esotropia: Do we Really Need to be Using Bifocals?

Introduction and PurposeMost strabismus specialists use bifocals for patients with convergence excess esotropia whose distance deviation is small. While this is a popular treatment modality, there is actually no good data to indicate that this should be considered a standard of care.Patients and MethodsIn patients for whom the distance deviation is small enough to allow for the development of binocular vision, my preference is to simply observe these patients. Most will improve with time. For those who do not, or who decompensate, surgery may be indicated.ResultsA careful review of the literature shows a lack of evidence to suggest that bifocals provide an effective treatment for this problem. Some data and theoretical concern may raise a concern over their use. Time and observation may be all that is necessary. There may be a role for surgical correction in these patients as well.ConclusionWhile there are theoretical advantages to the use of bifocals in patients with convergence excess esotropia, current data does not support the actual need for active treatment of these patients.

Contribution of binocular vision to the performance of complex manipulation tasks in 5–13 years 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.

Visual symmetry perception in early onset monocular blindness

Symmetry detection is impaired by abnormal binocular vision development such as in amblyopia. However, the detection of symmetry has never been investigated in cases where input from one eye is profoundly compromised. Testing monocularly blind (MB) individuals represents a unique opportunity to investigate whether symmetry salience relies on a normally developed binocular visual system. In a visual symmetry detection task using dot patterns, congenitally MB showed comparable accuracy to normally sighted individuals viewing monocularly. This included better detection of vertically than horizontally symmetric patterns. However, the MB were slower than controls in detecting a symmetrical pattern. In a control target-detection task, no significant differences in performance were observed between these groups. Overall, normal developing binocular vision does not appear necessary for the visual system to detect the presence of visual symmetry. However, optimal detection mechanisms may be dependent on binocular summation or other processes dependent on input from both eyes.

Symmetry Detection in Visual Impairment: Behavioral Evidence and Neural Correlates

Bilateral symmetry is an extremely salient feature for the human visual system. An interesting issue is whether the perceptual salience of symmetry is rooted in normal visual development. In this review, we discuss empirical work on visual and tactile symmetry detection in normally sighted and visually impaired individuals. On the one hand, available evidence suggests that efficient visual symmetry detection may need normal binocular vision development. On the other hand, converging evidence suggests that symmetry can develop as a principle of haptic perceptual organization in individuals lacking visual experience. Certain features of visual symmetry detection, however, such as the higher salience of the patterns containing a vertical axis of symmetry, do not systematically apply to the haptic modality. The neural correlates (revealed with neuroimaging) associated with visual and haptic symmetry detection are also discussed.

Development of Binocular Vision

AbstrakPenglihatan binokular secara harfiah berarti penglihatan dengan 2 mata dan dengan adanya penglihatan binokular, kita dapat melihat dunia dalam 3 dimensi meskipun bayangan yang jatuh pada kedua retina merupakan bayangan 2 dimensi. Penglihatan binokular juga memberikan beberapa keuntungan berupa ketajaman visual, kontras sensitivitas, dan lapangan pandang penglihatan yang lebih baik dibandingkan dengan penglihatan monokular. Penglihatan binokular normal memerlukan aksis visual yang jernih, fusi sensoris, dan fusi motoris. Pada manusia, periode sensitif dari perkembangan penglihatan binokular dimulai pada usia sekitar 3 bulan, mencapai puncaknya pada usia 1 hingga 3 tahun, telah berkembang sempurna pada usia 4 tahun dan secara perlahan menurun hingga berhenti pada usia 9 tahun. Berbagai hambatan, berupa hambatan sensoris, motoris,dan sentral, dalam jalur refleks sangat mungkin akan menghambat perkembangan dari penglihatan binokular terutama pada periode sensitif sewaktu 2 tahun pertama kehidupan.Kata kunci: penglihatan binokular, perkembangan, fusi, stereopsisAbstractBinocular vision literally means vision with two eyes and with binocular vision, we can see the world in three dimensions even though the images that fall on both of the retina were the 2-dimensional images. Binocular vision also provide some advantages included improved visual acuity, contrast sensitivity, and visual field compared with monocular vision. Normal binocular vision requires a clear visual axis, sensory fusion, and motoric fusion. In human, the sensitive period of binocular vision development began at around 3 months of age, reaching its peak at the age of 1 to 3 years, had developed completely at the age of 4 years and gradually declined until it stops at the age of 9 years. Various obstacles, such as sensory, motoric, and central obstacles, within the reflex pathway were very likely to inhibited the development of binocular vision, especially in sensitive period during the first 2 years of life.Keywords: binocular vision, development, fusion, stereopsis

Surgery for Infantile Esotropia: Is Timing Everything?

Infantile esotropia affects binocular alignment and development of binocular vision. Delayed correction may lead to loss of stereopsis. Waiting for the angle of deviation to stabilise prior to surgery does not impact overall postoperative outcomes greatly. Early surgical intervention produces better outcomes in terms of sensory and motor development, binocular vision and stereoacuity. The period of misalignment has the greatest effect on postoperative outcome therefore early surgery is recommended.