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• Human visual processing has biased sensitivities to gratings in various orientations. • Adults are usually least sensitive to oblique gratings (Oblique Effect). • Children are usually least sensitive to horizontal gratings (Horizontal Effect). • The horizontal effect is still present after four months with normal maturation. • Poor visual development may produce alternative patterns of meridional anisotropies. It is important to understand the development of meridional anisotropies in neurotypical children since those with poor visual development, such as amblyopia, can have different patterns of meridional anisotropies. While the oblique effect is usually observed in adults, neurotypical children who have normal 20/20 visual acuity tend to demonstrate a horizontal effect electrophysiologically. In this longitudinal study, orientation-specific visual evoked potentials (osVEPs) and psychophysical grating acuity were used to investigate the changes in the meridional anisotropies in children aged 3.8 to 9.2 years over two visits averaging four months apart. While it was hypothesized that the electrophysiological horizontal effect may shift towards an oblique effect, it was found that the electrophysiological horizontal effect persisted to be present in response to the suprathreshold moderate contrast 4 cycles-per-degree grating stimuli. Psychophysical grating acuity, however, demonstrated an oblique effect when assessed binocularly. In addition, a significant effect of visit, representing an increase in the average age over this period, was observed in the average osVEP C3 amplitudes (4.5 μV) and psychophysical grating acuity (0.28 octaves or approximately 1-line on the logMAR chart). These findings are relevant when evaluating amblyopia treatments and interventions, as it confirms the necessity to take into account of the effect of normal maturation and learning effects when evaluating young children. Special attention should also be given to children with early-onset myopia and high astigmatism even when their visual acuity is 20/20 as the electrophysiological findings are suggestive of poor visual development, which warrants further investigation. [ABSTRACT FROM AUTHOR]

There is currently a diverse array of treatment for amblyopia. In addition to the traditional penalization therapy, which has been used for over 200 years, there are not only more active treatments to recover the monocular visual loss of the amblyopic eye involving both behavioral (visual training) as well as non-invasive brain stimulation but also a variety of methods designed specifically to restore binocular function. Our understanding of visual function in general and of the etiology of the amblyopic loss in particular has progressed a great deal over the last 50 years and it is now time to take a more principled approach to how we treat, when we treat and why we treat., (Copyright © 2024 The Author. Published by Elsevier Ltd.. All rights reserved.)

Brief periods of monocular deprivation significantly modify binocular visual processing. For example, patching one eye for a few hours alters the inter-ocular balance, with the previously patched eye becoming dominant once the patch is removed. However, the contribution of higher-level visual processing to this phenomenon is still unclear. Here, we compared changes in sensory eye dominance produced by three types of monocular manipulations in adult participants with normal binocular vision. One eye was covered for 150 min using either an opaque patch, a diffusing lens, or a prism that inverted the image. All three manipulations altered dominance duration and predominance during binocular rivalry (BR) in favour of the treated eye and the time courses of the changes were similar. These results indicate that modifications of luminance or contrast are not strictly necessary to drive shifts in eye dominance, as both were unaltered in the prism condition. Next, we found that shifts in eye dominance were dependent on attentional demands during the monocular treatment period, providing support for the role of attentional eye selection in modulating eye dominance. Finally, we found relatively rapid build-up of the ocular dominance shift after the onset of monocular treatment. Taken together, our results suggest that modifications to monocular input alter inter-ocular balance via selective attentional mechanisms that bias output towards the deprived eye. Eye-based attention may play an important role in conditions where normal input to one eye is disrupted, such as childhood amblyopia. [ABSTRACT FROM AUTHOR]

Amblyopia is a neuro-developmental disorder of the visual cortex that arises from abnormal visual experience early in life. Amblyopia is clinically important because it is a major cause of vision loss in infants and young children. Amblyopia is also of basic interest because it reflects the neural impairment that occurs when normal visual development is disrupted. Amblyopia provides an ideal model for understanding when and how brain plasticity may be harnessed for recovery of function. Over the past two decades there has been a rekindling of interest in developing more effective methods for treating amblyopia, and for extending the treatment beyond the critical period, as exemplified by new clinical trials and new basic research studies. The focus of this review is on stereopsis and its potential for recovery. Impaired stereoscopic depth perception is the most common deficit associated with amblyopia under ordinary (binocular) viewing conditions (Webber & Wood, 2005). Our review of the extant literature suggests that this impairment may have a substantial impact on visuomotor tasks, difficulties in playing sports in children and locomoting safely in older adults. Furthermore, impaired stereopsis may also limit career options for amblyopes. Finally, stereopsis is more impacted in strabismic than in anisometropic amblyopia. Our review of the various approaches to treating amblyopia (patching, perceptual learning, videogames) suggests that there are several promising new approaches to recovering stereopsis in both anisometropic and strabismic amblyopes. However, recovery of stereoacuity may require more active treatment in strabismic than in anisometropic amblyopia. Individuals with strabismic amblyopia have a very low probability of improvement with monocular training; however they fare better with dichoptic training than with monocular training, and even better with direct stereo training.

Many patients with concussion experience visual symptoms following injury that lead to a diagnosis of convergence insufficiency, accommodative insufficiency, or saccadic dysfunction. However, these diagnostic categories are based on aggregates of clinical tests developed from a non-concussed population and therefore may not accurately describe visual deficits in the concussed population. Thus, we sought to understand individual metrics of visual dysfunction in chronically symptomatic post-concussion patients. This retrospective cross-sectional study included patients examined at the multidisciplinary concussion clinic (MDCC) at Boston Children's Hospital over four years. Patients aged 5-21 years who had a complete assessment of eye alignment, vergence, accommodation, and visual tracking, and had visual acuity better than or equal to 20/30 in each eye were included. Patients with history of amblyopia, strabismus, or ocular pathology were excluded. Chart review yielded 116 patients who met inclusion criteria (median age 15 years, 64% female). The majority of patients (52%) experienced a single concussion and most were sports-related (50%). Clinical data show vergence, accommodation, or visual tracking deficits in 95% of patients. A receded near point of convergence (NPC, 70/116) and reduced accommodative amplitude (63/116) were the most common deficits. Both NPC and accommodative amplitude were significantly correlated with one another (r = -0.5) and with measures of visual tracking (r = -0.34). Patients with chronic post-concussion symptoms show deficits in individual metrics of vergence, accommodation and visual tracking. The high incidence of these deficits, specifically NPC and accommodative amplitude, highlights the need for a detailed sensorimotor evaluation to guide personalized treatment following concussion. [ABSTRACT FROM AUTHOR]

Classic studies of ocular dominance plasticity in early development showed that monocular deprivation suppresses the neural representation and visual function of the deprived eye. However, recent studies have shown that a short period of monocular deprivation (<3 h) in normal adult humans, shifts sensory eye dominance in favor of the deprived eye. How can these opposing effects be reconciled? Here we argue that there are two systems acting in opposition at different time scales. A fast acting, stabilizing, homeostatic system that rapidly decreases gain in the non-deprived eye or increases gain in the deprived eye, and a relatively sluggish system that shifts balance toward the non-deprived eye, in an effort to reduce input of little utility to active vision. If true, then continuous deprivation should produce a biphasic effect on interocular balance, first shifting balance away from the non-deprived eye, then towards it. Here we investigated the time course of the deprivation effect by monocularly depriving typical adults for 10 h and conducting tests of sensory eye balance at six intervening time points. Consistent with previous short-term deprivation work, we found shifts in sensory eye dominance away from the non-deprived eye up until approximately 5 h. We then observed a turning point, with balance shifting back towards the non-deprived eye, -, a biphasic effect. We argue that this turning point marks where the rapid homeostatic response saturates and is overtaken by the slower system responsible for suppressing monocular input of limited utility. [ABSTRACT FROM AUTHOR]

Recent work has transformed our ideas about the neural mechanisms, behavioral consequences and effective therapies for amblyopia. Since the 1700's, the clinical treatment for amblyopia has consisted of patching or penalizing the strong eye, to force the "lazy" amblyopic eye, to work. This treatment has generally been limited to infants and young children during a sensitive period of development. Over the last 20 years we have learned much about the nature and neural mechanisms underlying the loss of spatial and binocular vision in amblyopia, and that a degree of neural plasticity persists well beyond the sensitive period. Importantly, the last decade has seen a resurgence of research into new approaches to the treatment of amblyopia both in children and adults, which emphasize that monocular therapies may not be the most effective for the fundamentally binocular disorder that is amblyopia. These approaches include perceptual learning, video game play and binocular methods aimed at reducing inhibition of the amblyopic eye by the strong fellow eye, and enhancing binocular fusion and stereopsis. This review focuses on the what we've learned over the past 20 years or so, and will highlight both the successes of these new treatment approaches in labs around the world, and their failures in clinical trials. Reconciling these results raises important new questions that may help to focus future directions. [ABSTRACT FROM AUTHOR]

Many people with stereo-deficiency cannot perform stereoacuity tasks at any binocular disparity, so their threshold cannot be measured. We developed a generally useful new composite stereodepth or CSD score, with range 0 to 20, that combines stereoacuity (from 0 to 13.3) and percent correct (13.3 to 20) into a single index. CSD allows differences in stereodepth performance to be measured across groups when thresholds cannot be reliably measured, and across time when individuals gain stereodepth perception during training. We used CSD scores to assess the benefit of unequal (mixed) left- and right-eye contrast during dichoptic stereoacuity training in people with amblyopia. Nineteen adult participants with anisometropic amblyopia were assigned randomly to 10 sessions of either mixed-contrast or fixed-contrast training. Stimuli were rectangles, one above the other, viewed through a four-mirror stereoscope. Participants indicated which rectangle appeared closer. A staircase controlled disparity within the stimulus. CSD improvement was better by 1.6 CSD units for participants who received mixed-contrast training. Thus, mixed-contrast stereo training was more effective than fixed-contrast training in adults with anisometropic amblyopia. [ABSTRACT FROM AUTHOR]

In amblyopia, there is an interocular suppressive imbalance that results in the fixing eye dominating perception. In this study, we aimed to determine whether these suppressive interactions were narrowband and tuned for spatial frequency or broadband and independent of spatial frequency. We measured the contrast sensitivity and masking functions of fifteen amblyopic subjects and seventeen control subjects using the quick Contrast Sensitivity Function (qCSF) approach (Lesmes, Lu, Baek, & Albright, 2010). We first measured the monocular sensitivity functions of each participant and thereafter corrected for it. We then measured masking sensitivity functions for low, mid and high spatial frequency masks, normalized to their visibility. In the control group, we observed that the strength of dichoptic masking is equivalent between the two eyes. It is also tuned such that masking by low spatial frequencies in one eye mainly affects low spatial frequencies in the other eye and masking by high spatial frequencies mainly affects high spatial frequencies. In amblyopes, although the interocular masking is also tuned for spatial frequency, it is not equivalent between the two eyes: the masking effect from the amblyopic to fixing eye is weaker than the other way around. The asymmetry observed in the strength of masking between the two eyes in amblyopia is tuned for spatial frequency. It is not the consequence of the contrast sensitivity deficit of the amblyopic eye nor is it the consequence of abnormally strong masking from the fixing eye. Rather it is due to an abnormally weak masking strength by the amblyopic eye per se. [ABSTRACT FROM AUTHOR]

Mach and Hering had early advanced a model of spatial visual processing featuring an antagonistic interaction between adjoining areas in the visual field. Spatial opponency was one of the first findings when single-unit studies of the retina were begun. Not long afterwards psychophysical experiments revealed a center-surround organization closely matching that found in the mammalian retina. It hinged on the demonstration of reduction of sensitivity in a small patch of the visual field when its surround was changed from dark to bright. Because such patterns inevitably produce borders, well-known phenomena of border interaction could be seen as providing alternative explanations, whose substrate would most likely be in the visual cortex. These competing viewpoints are discussed especially as they pertain to the recent demonstration of spatial differences in the center/surround organization between the normal and affected eyes of amblyopes. To the extent that most findings favor a retinal site for the psychophysically measured antaaonism, and that evidence is accumulating for a direct effect on the mammalian retina of stimulus manipulation during visual development, the difference in spatial parameters of center/surround antagonism in amblyopia Suggests that the dysfunction in amblyopia begins already in the retina. (C) 2004 Elsevier Ltd. All rights reserved.

New digital approaches allow stereovision to be assessed with greater precision than current clinical stereo tests. Those current tests present a relatively narrow range of stimulus disparities in coarsely quantized steps. With dichoptic treatments for amblyopia emerging, more accurate assessment of especially coarse stereopsis becomes increasingly important for verifying their aim to improve 3D vision. We used digital testing in subjects of a large age range (4–59 years), with groups having both normal (n = 34) and impaired binocular vision due to unilateral amblyopia, with or without strabismus (n = 27). Random-dot stimuli were presented on a 3D monitor with shutter glasses. The test applies adaptive procedures to measure psychometric functions and provides thresholds with associated confidence intervals. Digital thresholds for controls (range 11–160 arcsec) and stereodeficient subjects (range 43–911 arcsec) were compared to the TNO, a standard clinical test which uses similar random-dot targets presented with anaglyph glasses. Agreement between digital and TNO thresholds varied with the level of stereopsis. Stereoacuity was measurable in several subjects who failed on the TNO. With the digital test we found good repeatability for both groups, with the indication of a small learning effect for subjects with coarse stereopsis. Thus, assessment of all target groups for new tests is important, and repeated testing before therapy may avoid confusing learning and treatment effects. Our digital approach supplies a large range of accurate stereo data in children and adults; together with its associated measure of variability, it will be useful in longitudinal treatment studies. [ABSTRACT FROM AUTHOR]

In this study, we aimed to explore an objective, sensitive and quantitative measurement of interocular suppression in strabismic amblyopia. We compared 11 strabismic subjects with 12 normal vision subjects to explore the different response characterizations in normal eyes, nondominant and dominant eyes of strabismic subjects by using steady-state motion visual evoked potentials (SSMVEPs). Stimulation at different temporal frequencies was presented to two eyes by using an interocular dichoptic technique. Furthermore, canonical correlation analysis (CCA), signal-to-noise ratio (SNR) and some statistical methods, such as the paired t-test, analysis of variance (ANOVA) and correlation analysis, were used to analyze electroencephalography (EEG) signals. We proposed two indices-divergence J and suppression imbalance (SI) to describe the deficits in interocular suppression-and one index - mask attenuation coefficient (MAC)- to describe the influence of a dichoptic mask from the dominant eyes to nondominant eyes of strabismic subjects. A significant difference was found between nondominant and dominant eyes of strabismic subjects in SSMVEP response and SNR value while no apparent difference was observed between the two eyes in subjects with normal vision. There was a strong linear correlation between divergence J, SI and visual acuity difference of two eyes both in strabismic amblyopia and normal vision. A linear correlation was also found between visual acuity difference and MAC in patients with strabismic amblyopia. Our findings suggest that SSMVEPs can be an objective and quantitative method for measuring the interocular suppression in strabismus and assessing the deficits of strabismic amblyopia. [ABSTRACT FROM AUTHOR]

Amblyopia is associated with a range of well-known visual spatial deficits, which include reduced contrast sensitivity, spatial distortions, interocular suppression, and impaired stereopsis. Previous work has also pointed to deficits in processing dynamic visual information, but it is unknown whether these deficits influence performance under binocular conditions. We examined the effects of temporal modulation on contrast sensitivity and binocular interactions in a preliminary study of 8 adults with amblyopia and 14 normally-sighted control subjects. For each observer, we measured interocular balance and stereopsis thresholds with binocular flicker across a range of four temporal (0, 4, 7.5, and 12 Hz) and spatial (1, 2, 4, and 8 cpd) frequencies. Interocular balance was estimated by varying the relative contrast of dichoptic letter pairs to produce perceptual reports of each letter with equal frequency, and stereopsis thresholds were measured by determining the minimum disparity at which subjects identified a front-depth target with 75% accuracy. Consistent with previous findings, we observed greater interocular imbalance and impaired stereoacuity at high spatial frequencies in amblyopes. In contrast, the effects of temporal frequency on performance were smaller: across both groups, interocular imbalance was largest at mid-to-low temporal frequencies, and stereopsis thresholds were unaffected by temporal frequency. Our results suggest that there may be a previously unreported effect of temporal frequency on interocular balance, as well as a possible dissociation between the effects of flicker on interocular balance and stereopsis. [ABSTRACT FROM AUTHOR]

Previous studies have reported compromised reading ability in children with amblyopia. Standardized psychoeducational test norms have not been used; therefore, the practical consequences of poor reading ability, such as eligibility for reading supports at school, have not been assessed. Furthermore, several studies have used atypical reading conditions such as monocular or distant viewing. It is also not clear how amblyopia treatment impacts reading ability. Thus, the goal of this study was to use standardized tests to compare binocular reading performance in children treated for amblyopia to that of a large normative sample, as well as to the types of control groups used in previous studies. Children treated for strabismic or anisometropic amblyopia (N = 14) were compared to children treated for strabismus without amblyopia (N = 12) and to children with healthy vision (N = 39). Visual acuity, stereoacuity, interocular suppression, intellectual functioning, oral single-word reading (TOWRE-2), and oral paragraph reading (GORT-5) were assessed. The control group showed significantly higher single-word reading accuracy than the amblyopia and strabismus groups. However, mean performance for all groups was within the average range of the normative sample. While mean scores were in the average range, six children (four amblyopia, two strabismus) performed below average on the single-word reading task; four of these children also showed below average paragraph reading. Reading scores were not correlated with visual acuity in the patient groups. The results raise the possibility that both strabismus and amblyopia can disrupt reading ability, even following successful treatment, to an extent that might benefit from reading supports at school. [ABSTRACT FROM AUTHOR]

Amblyopia is associated with impaired visual acuity (VA) and reduced fixation stability (FS). To assess whether impaired VA may cause reduced FS, the effects of retinal-defocus-induced visual acuity reductions on FS were measured in observers with amblyopia and controls. Fixational eye movements were measured in 8 patients with amblyopia and 12 controls. Monocular near VA of a subset of controls (n = 5) was then varied from 20/20 to 20/100 using convex lenses. The amblyopia group completed three monocular conditions; 1) amblyopic eye fixating, 2) fellow eye fixating and 3) fellow eye fixating with VA reduced to match the amblyopic eye. Fixational eye movements were quantified using bivariate contour ellipse area (BCEA) and microsaccadic amplitude. Amblyopic eye BCEA was significantly larger with increased microsaccadic amplitude compared to the fellow eye and control eyes. BCEA and VA were positively correlated for amblyopic eyes. VA impairments induced by retinal defocus did not reduce FS in controls or the fellow eye of observers with amblyopia, even when fellow eye VA was matched to that of the amblyopic eye. This suggests that reduced FS in amblyopic eyes cannot be simulated by acute VA reductions. Therefore, reduced amblyopic eye FS may not be a direct consequence of the VA loss alone. As in previous studies, a correlation between BCEA and VA for amblyopic eyes was observed. This relationship could be due to a third, mediating variable or an effect of fixational eye movements on VA. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

This Special Issue describes the impact of visual impairment on visuomotor function. It includes contributions that examine gaze control in conditions associated with abnormal visual development such as amblyopia, dyslexia and neurofibromatosis as well as disorders associated with field loss later in life, such as macular degeneration and stroke. Specifically, the papers address both gaze holding (fixation), and gaze-following behavior (single saccades, sequences of saccades and smooth-pursuit) that characterize active vision in daily life and evaluate the influence of both pathological and simulated field loss. Several papers address the challenges to reading and visual search; describing how the patterns of eye movements in these real-world tasks adapt to visual impairment and highlighting how they could serve as diagnostic markers of visuomotor function. [ABSTRACT FROM AUTHOR]

• Stereopsis was identified in the majority (59%) of our amblyopic participants. • This compares to 45% who had measurable stereoacuity on the Randot Preschool Test. • Equivalent internal disparity noise was elevated in our amblyopic participants. People with amblyopia demonstrate a reduced ability to judge depth using stereopsis. Our understanding of this deficit is limited, as standard clinical stereo tests may not be suited to give a quantitative account of the residual stereo ability in amblyopia. In this study we used a stereo test designed specifically for that purpose. Participants identified the location of a disparity-defined odd-one-out target within a random-dot display. We tested 29 amblyopic (3 strabismic, 17 anisometropic, 9 mixed) participants and 17 control participants. We obtained stereoacuity thresholds from 59% of our amblyopic participants. There was a factor of two difference between the median stereoacuity of our amblyopic (103 arcsec) and control (56 arcsec) groups. We used the equivalent noise method to evaluate the role of equivalent internal noise and processing efficiency in amblyopic stereopsis. Using the linear amplifier model (LAM), we determined the threshold difference was due to a greater equivalent internal noise in the amblyopic group (238 vs 135 arcsec), with no significant difference in processing efficiency. A multiple linear regression determined 56% of the stereoacuity variance within the amblyopic group was predicted by the two LAM parameters, with equivalent internal noise predicting 46% alone. Analysis of control group data aligned with our previous work, finding that trade-offs between equivalent internal noise and efficiency play a greater role. Our results allow a better understanding of what is limiting amblyopic performance in our task. We find this to be a reduced quality of disparity signals in the input to the task-specific processing. [ABSTRACT FROM AUTHOR]

Dichoptic training is a recent focus of research on perceptual learning in adults with amblyopia, but whether and how dichoptic training is superior to traditional monocular training is unclear. Here we investigated whether dichoptic training could further boost visual acuity and stereoacuity in monocularly well-trained adult amblyopic participants. During dichoptic training the participants used the amblyopic eye to practice a contrast discrimination task, while a band-filtered noise masker was simultaneously presented in the non-amblyopic fellow eye. Dichoptic learning was indexed by the increase of maximal tolerable noise contrast for successful contrast discrimination in the amblyopic eye. The results showed that practice tripled maximal tolerable noise contrast in 13 monocularly well-trained amblyopic participants. Moreover, the training further improved stereoacuity by 27% beyond the 55% gain from previous monocular training, but unchanged visual acuity of the amblyopic eyes. Therefore our dichoptic training method may produce extra gains of stereoacuity, but not visual acuity, in adults with amblyopia after monocular training. [ABSTRACT FROM AUTHOR]

The gold-standard treatment for childhood amblyopia remains patching or penalizing the fellow eye, resulting in an average of about a one line (0.1 logMAR) improvement in visual acuity following ≈120 h of patching in children 3-8 years old. However, compliance with patching and other treatment options is often poor. In contrast, fast-paced action video games can be highly engaging, and have been shown to yield broad-based improvements in vision and attention in adult amblyopia. Here, we pilot-tested a custom-made action video game to treat children with amblyopia. Twenty-one (n = 21) children (mean age 9.95 ± 3.14 [se]) with unilateral amblyopia (n = 12 anisometropic and n = 9 strabismic) completed 20 h of game play either monocularly, with the fellow eye patched (n = 11), or dichoptically, with reduced contrast to the fellow eye (n = 10). Participants were assessed for visual acuity (VA), stereo acuity and reading speed at baseline, and following 10 and 20 h of play. Additional exploratory analyses examined improvements after 6-10 weeks of completion of training (follow-up). Following 20 h of training, VA improved, on average, by 0.14 logMAR (≈38%) for the dichoptic group and by 0.06 logMAR (≈15%) for the monocular group. Similarly, stereoacuity improved by 0.07 log arcsec (≈17%) following dichoptic training, and by 0.06 log arcsec (≈15%) following monocular training. Across both treatment groups, 7 of the 12 individuals with anisometropic amblyopia showed improvement in stereoacuity, whereas only 1 of the 9 strabismic individuals improved. Most improvements were largely retained at follow-up. Our feasibility study therefore suggests that the action video game approach may be used as an effective adjunct treatment for amblyopia in children, achieving results similar to those of the gold-standard treatment in shorter duration. [ABSTRACT FROM AUTHOR]

Recently, psychophysical studies have shown that humans with amblyopia do have binocular function that is not normally revealed due to dominant suppressive interactions under normal viewing conditions. Here we use magnetoencephalography (MEG) combined with dichoptic visual stimulation to investigate the underlying binocular function in humans with amblyopia for stimuli that, because of their temporal properties, would be expected to bypass suppressive effects and to reveal any underlying binocular function. We recorded contrast response functions in visual cortical area V1 of amblyopes and normal observers using a steady state visually evoked responses (SSVER) protocol. We used stimuli that were frequency-tagged at 4Hz and 6Hz that allowed identification of the responses from each eye and were of a sufficiently high temporal frequency (>3Hz) to bypass suppression. To characterize binocular function, we compared dichoptic masking between the two eyes in normal and amblyopic participants as well as interocular phase differences in the two groups. We observed that the primary visual cortex responds less to the stimulation of the amblyopic eye compared to the fellow eye. The pattern of interaction in the amblyopic visual system however was not significantly different between the amblyopic and fellow eyes. However, the amblyopic suppressive interactions were lower than those observed in the binocular system of our normal observers. Furthermore, we identified an interocular processing delay of approximately 20ms in our amblyopic group. To conclude, when suppression is greatly reduced, such as the case with our stimulation above 3Hz, the amblyopic visual system exhibits a lack of binocular interactions. [ABSTRACT FROM AUTHOR]

We investigated the potential causal relationships between anisometropia, amblyopia and strabismus, specifically to determine whether either amblyopia or strabismus interfered with emmetropization. We analyzed data from non-human primates that were relevant to the co-existence of anisometropia, amblyopia and strabismus in children. We relied on interocular comparisons of spatial vision and refractive development in animals reared with 1) monocular form deprivation; 2) anisometropia optically imposed by either contact lenses or spectacle lenses; 3) organic amblyopia produced by laser ablation of the fovea; and 4) strabismus that was either optically imposed with prisms or produced by either surgical or pharmacological manipulation of the extraocular muscles. Hyperopic anisometropia imposed early in life produced amblyopia in a dose-dependent manner. However, when potential methodological confounds were taken into account, there was no support for the hypothesis that the presence of amblyopia interferes with emmetropization or promotes hyperopia or that the degree of image degradation determines the direction of eye growth. To the contrary, there was strong evidence that amblyopic eyes were able to detect the presence of a refractive error and alter ocular growth to eliminate the ametropia. On the other hand, early onset strabismus, both optically and surgically imposed, disrupted the emmetropization process producing anisometropia. In surgical strabismus, the deviating eyes were typically more hyperopic than their fellow fixating eyes. The results show that early hyperopic anisometropia is a significant risk factor for amblyopia. Early esotropia can trigger the onset of both anisometropia and amblyopia. However, amblyopia, in isolation, does not pose a significant risk for the development of hyperopia or anisometropia. [ABSTRACT FROM AUTHOR]

In patients with anisometropic or strabismic amblyopia, interocular suppression can be minimized by presenting high contrast stimulus elements to the amblyopic eye and lower contrast elements to the fellow eye. This suggests a structurally intact binocular visual system that is functionally suppressed. We investigated whether suppression can also be overcome by contrast balancing in children with deprivation amblyopia due to childhood cataracts. To quantify interocular contrast balance, contrast interference thresholds were measured using an established dichoptic global motion technique for 21 children with deprivation amblyopia, 14 with anisometropic or mixed strabismic/anisometropic amblyopia and 10 visually normal children (mean age mean=9.9years, range 5-16years). We found that interocular suppression could be overcome by contrast balancing in most children with deprivation amblyopia, at least intermittently, and all children with anisometropic or mixed anisometropic/strabismic amblyopia. However, children with deprivation amblyopia due to early unilateral or bilateral cataracts could tolerate only very low contrast levels to the stronger eye indicating strong suppression. Our results suggest that treatment options reliant on contrast balanced dichoptic presentation could be attempted in a subset of children with deprivation amblyopia. [ABSTRACT FROM AUTHOR]

Global motion sensitivity in typically developing children depends on the spatial (Δx) and temporal (Δt) displacement parameters of the motion stimulus. Specifically, sensitivity for small Δx values matures at a later age, suggesting it may be the most vulnerable to damage by amblyopia. To explore this possibility, we compared motion coherence thresholds of children with amblyopia (7-14years old) to age-matched controls. Three Δx values were used with two Δt values, yielding six conditions covering a range of speeds (0.3-30deg/s). We predicted children with amblyopia would show normal coherence thresholds for the same parameters on which 5-year-olds previously demonstrated mature performance, and elevated coherence thresholds for parameters on which 5-year-olds demonstrated immaturities. Consistent with this, we found that children with amblyopia showed deficits with amblyopic eye viewing compared to controls for small and medium Δx values, regardless of Δt value. The fellow eye showed similar results at the smaller Δt. These results confirm that global motion perception in children with amblyopia is particularly deficient at the finer spatial scales that typically mature later in development. An additional implication is that carefully designed stimuli that are adequately sensitive must be used to assess global motion function in developmental disorders. Stimulus parameters for which performance matures early in life may not reveal global motion perception deficits. [ABSTRACT FROM AUTHOR]

In the past 20 years, there has been a great advancement in knowledge pertaining to compliance with amblyopia treatments. The occlusion dose monitor introduced quantitative monitoring methods in patching, which sparked our initial understanding of the dose–response relationship for patching amblyopia treatment. This review focuses on current compliance knowledge and the impact it has on patching and atropine amblyopia treatment. [ABSTRACT FROM AUTHOR]

There is growing evidence that abnormal binocular interactions play a key role in amblyopia. In particular, stronger suppression of the amblyopic eye has been associated with poorer amblyopic eye visual acuity and a new therapy has been described that directly targets binocular function and has been found to improve both monocular and binocular vision in adults and children with amblyopia. Furthermore, non-invasive brain stimulation techniques that alter excitation and inhibition within the visual cortex have been shown to improve vision in the amblyopic eye. The aim of this review is to summarize this previous work and interpret the therapeutic effects of binocular therapy and non-invasive brain stimulation in the context of three potential neural mechanisms; active inhibition of signals from the amblyopic eye, attenuation of information from the amblyopic eye and metaplasticity of synaptic long term potentiation and long term depression. [ABSTRACT FROM AUTHOR]

Previous studies have employed different experimental approaches to enhance visual function in adults with amblyopia including perceptual learning, videogame play, and dichoptic training. Here, we evaluated the efficacy of a novel dichoptic action videogame combining all three approaches. This experimental intervention was compared to a conventional, yet unstudied method of supervised occlusion while watching movies. Adults with unilateral amblyopia were assigned to either play the dichoptic action game ( n = 23; ‘game’ group), or to watch movies monocularly while the fellow eye was patched ( n = 15; ‘movies’ group) for a total of 40 hours. Following training, visual acuity (VA) improved on average by ≈0.14 logMAR (≈28%) in the game group, with improvements noted in both anisometropic and strabismic patients. This improvement is similar to that obtained following perceptual learning, video game play or dichoptic training. Surprisingly, patients with anisometropic amblyopia in the movies group showed similar improvement, revealing a greater impact of supervised occlusion in adults than typically thought. Stereoacuity, reading speed, and contrast sensitivity improved more for game group participants compared with movies group participants. Most improvements were largely retained following a 2-month no-contact period. This novel video game, which combines action gaming, perceptual learning and dichoptic presentation, results in VA improvements equivalent to those previously documented with each of these techniques alone. Our game intervention led to greater improvement than control training in a variety of visual functions, thus suggesting that this approach has promise for the treatment of adult amblyopia. [ABSTRACT FROM AUTHOR]

Although the neural locus of strabismic amblyopia has been shown to lie at the first site of binocular integration, first in cat and then in primate, an adequate mechanism is still lacking. Here we hypothesise that increased temporal dispersion of LGN X-cell afferents driven by the deviating eye onto single cortical neurons may provide a neural mechanism for strabismic amblyopia. This idea was investigated via single cell extracellular recordings of 93 X and 50 Y type LGN neurons from strabismic and normal cats. Both X and Y neurons driven by the non-deviating eye showed shorter latencies than those driven by either the strabismic or normal eyes. Also the mean latency difference between X and Y neurons was much greater for the strabismic cells compared with the other two groups. The incidence of lagged X-cells driven by the deviating eye of the strabismic cats was higher than that of LGN X-cells from normal animals. Remarkably, none of the cells recorded from the laminae driven by the non-deviating eye were of the lagged class. A simple computational model was constructed in which a mixture of lagged and non-lagged afferents converge on to single cortical neurons. Model cut-off spatial frequencies to a moving grating stimulus were sensitive to the temporal dispersion of the geniculate afferents. Thus strabismic amblyopia could be viewed as a lack of developmental tuning of geniculate lags for neurons driven by the amblyopic eye. Monocular control of fixation by the non-deviating eye is associated with reduced incidence of lagged neurons, suggesting that in normal vision, lagged neurons might play a role in maintaining binocular connections for cortical neurons. [ABSTRACT FROM AUTHOR]

Adults with a history of unilateral amblyopia and abnormal binocularity have a range of visual deficits, with some of the ‘higher’ levels ones generalizing to their dominant (non-amblyopic) eye and linked to widespread binocular cortical network dysfunctions. Our interests are in how these problems also impact on their hand action control in real-world situations. We investigated whether eye-hand coordination deficits, known to exist in amblyopia when goal objects are presented under full-lighting and at high contrast, are exacerbated under low object-background contrast or in dim lighting/low visibility conditions. Hand movement parameters were recorded and quantified in 13 amblyopia and 13 control subjects while they reached-to-precision grasp objects using both eyes together or just their dominant or amblyopic/non-dominant eye alone under these 3 task conditions. Compared to controls, the amblyopia subjects spent significantly longer in preparing their movements, in the initial (planned) periods of their reach and grasp and in applying their grip, while making more reach and grasp errors under all 3 views and tasks. Deficits in planning and controlling the grasp were also selectively accentuated in the low contrast condition, but with no evidence of relatively worse performance under low environmental illumination. We suggest that the dysfunctions in amblyopia are associated with generalized difficulties in obtaining reliable visual evidence about the target’s 3D properties during movement planning and in selecting and guiding the proper course of action, especially when segregating the object from background is more challenging. [ABSTRACT FROM AUTHOR]

Amblyopia screening during childhood is critical for early detection and successful treatment. In the current study, we develop and evaluate a screening method that exploits the imbalanced interocular inhibition between amblyopic and fellow eyes. In nineteen subjects with anisometropic amblyopia and twenty-two age-matched subjects with myopia, we measured the area under the contrast sensitivity functions (AUCSFs) in eight monocular conditions defined by the tested eye (left, right), patching of the untested eye (translucent, opaque), and refractive status (corrected, uncorrected). For each tested eye, we defined the inhibition index as the ratio between the AUCSF values obtained in the translucent and opaque patching conditions of the untested eye. To evaluate the screening potential of the inhibition index, we compared results from patients with amblyopia and myopia. With and without optical correction, the index was significantly lower in the amblyopic eye than in the fellow eye of the amblyopic subjects and both eyes of the myopic subjects. No significant difference was found among the two eyes of the myopic subjects and the fellow eyes of the amblyopic subjects. With the inhibition index as the predictor, a logistic regression model successfully discriminated amblyopic eyes from myopic eyes with 100% accuracy in the uncorrected condition. In the corrected condition, with the inhibition index and interocular visual acuity difference as predictors, amblyopic eyes were likewise discriminated from myopic eyes with 100% accuracy. This pattern of CSF changes, caused by the different patching modes of the untested eye, provides a potential CSF signature to discriminate anisometropic amblyopia from myopia. [ABSTRACT FROM AUTHOR]

Randomized clinical trial (RCT) study design leads to one of the highest levels of evidence, and is a preferred study design over cohort studies, because randomization reduces bias and maximizes the chance that even unknown confounding factors will be balanced between treatment groups. Recent randomized clinical trials and observational studies in amblyopia can be taken together to formulate an evidence-based approach to amblyopia treatment, which is presented in this review. When designing future clinical studies of amblyopia treatment, issues such as regression to the mean, sample size and trial duration must be considered, since each may impact study results and conclusions. [ABSTRACT FROM AUTHOR]

Deprivation of patterned vision of frontal eyed mammals early in postnatal life alters structural and functional attributes of neurones in the central visual pathways, and can produce severe impairments of the vision of the deprived eye that resemble the visual loss observed in human amblyopia. A traditional approach to treatment of amblyopia has been the occlusion of the stronger fellow eye in order to force use of the weaker eye and thereby strengthen its connections in the visual cortex. Although this monocular treatment strategy can be effective at promoting recovery of visual acuity of the amblyopic eye, such binocular visual functions as stereoscopic vision often remain impaired due in part to the lack of concordant vision during the period of unilateral occlusion. The recent development of binocular approaches for treatment of amblyopia that improve the possibility for binocular interaction have achieved success in promoting visual recovery. The full and rapid recovery of visual acuity observed in amblyopic kittens placed in complete darkness is an example of a binocular treatment whose success may in part derive from a restored balance of visually-driven neural activity. In the current study we examined as an alternative to dark rearing the efficacy of binocular lid suture (BLS) to stimulate anatomical and visual recovery from a preceding amblyogenic period of monocular deprivation. In the dorsal lateral geniculate nucleus (dLGN) of monocularly deprived kittens, darkness or BLS for 10 days produced a complete recovery of neurone soma size within initially deprived layers. The growth of neurone somata within initially deprived dLGN layers after darkness or BLS was accompanied by an increase in neurotrophin-4/5 labeling within these layers. Although anatomical recovery was observed in both recovery conditions, BLS failed to promote any improvement of the visual acuity of the deprived eye no matter whether it followed immediately or was delayed with respect to the prior period of monocular deprivation. Notwithstanding the lack of visual recovery with BLS, all animals in the BLS condition that were subsequently placed in darkness exhibited a substantial recovery of visual acuity in the amblyopic eye. We conclude that the balanced binocular visual input provided by BLS does not stimulate the collection of neural events necessary to support recovery from amblyopia. The complete absence of visually-driven activity that occurs with dark rearing evidently plays an important role in the recovery process. [ABSTRACT FROM AUTHOR]

Amblyopia is a visual disorder caused by poorly coordinated binocular input during development. Little is known about the impact of amblyopia on the white matter within the visual system. We studied the properties of six major visual white-matter pathways in a group of adults with amblyopia ( n = 10) and matched controls ( n = 10) using diffusion weighted imaging (DWI) and fiber tractography. While we did not find significant differences in diffusion properties in cortico-cortical pathways, patients with amblyopia exhibited increased mean diffusivity in thalamo-cortical visual pathways. These findings suggest that amblyopia may systematically alter the white matter properties of early visual pathways. [ABSTRACT FROM AUTHOR]

A number of previous reports have suggested that the processing of second-order stimuli by the amblyopic eye (AE) is defective and that the fellow non-amblyopic eye (NAE) also exhibits an anomaly. Second-order stimuli involve extra-striate as well as striate processing and provide a means of exploring the extent of the cortical anomaly in amblyopia using psychophysics. We use a range of different second-order stimuli to investigate how general the deficit is for detecting second-order stimuli in adult amblyopes. We compare these results to our previously published adult normative database using the same stimuli and approach to determine the extent to which the detection of these stimuli is defective for both amblyopic and non-amblyopic eye stimulation. The results suggest that the second-order deficit affects a wide range of second-order stimuli, and by implication a large area of extra-striate cortex, both dorsally and ventrally. The NAE is affected only in motion-defined form judgments, suggesting a difference in the degree to which ocular dominance is disrupted in dorsal and ventral extra-striate regions. [ABSTRACT FROM AUTHOR]

Abnormal visual experience during childhood often leads to amblyopia, with strong links to binocular dysfunction that can include poor acuity in both eyes, especially in central vision. In animal models of amblyopia, the non-deprived eye is often considered normal and what limits binocular acuity. This leaves open the question whether monocular deprivation (MD) induces binocular dysfunction similar to what is found in amblyopia. In previous studies of MD cats, we found a loss of excitatory receptors restricted to the central visual field representation in visual cortex (V1), including both eyes’ columns. This led us to ask two questions about the effects of MD: how quickly are receptors lost in V1? and is there an impact on binocular acuity? We found that just a few hours of MD caused a rapid loss of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor proteins across all of V1. But after a few days of MD, there was recovery in the visual periphery, leaving a loss of AMPA receptors only in the central region of V1. We reared animals with early MD followed by a long period of binocular vision and found binocular acuity deficits that were greatest in the central visual field. Our results suggest that the greater binocular acuity deficits in the central visual field are driven in part by the long-term loss of AMPA receptors in the central region of V1. [ABSTRACT FROM AUTHOR]

Dichoptic training is designed to promote binocular vision in patients with amblyopia. Initial studies have found that the training effects transfer to both binocular (stereopsis) and monocular (recognition acuity) visual functions. The aim of this study was to assess whether dichoptic training effects also transfer to contrast sensitivity (CS) in adults with amblyopia. We analyzed CS data from 30 adults who had taken part in one of two previous dichoptic training studies and assessed whether the changes in CS exceeded the 95% confidence intervals for change based on test–retest data from a separate group of observers with amblyopia. CS was measured using Gabor patches (0.5, 3 and 10 cpd) before and after 10 days of dichoptic training. Training was delivered using a dichoptic video game viewed through video goggles ( n = 15) or on an iPod touch equipped with a lenticular overlay screen ( n = 15). In the iPod touch study, training was combined with anodal transcranial direct current stimulation of the visual cortex. We found that dichoptic training significantly improved CS across all spatial frequencies tested for both groups. These results suggest that dichoptic training modifies the sensitivity of the neural systems that underpin monocular CS. [ABSTRACT FROM AUTHOR]

The visual evoked potential (VEP) generated by the amblyopic visual system demonstrates reduced amplitude, prolonged latency, and increased variation in response timing (phase-misalignment). This study examined VEPs before and after occlusion therapy (OT) and whether phase-misalignment can account for the amblyopic VEP deficits. VEPs were recorded to 0.5–4 cycles/degree gratings in 10 amblyopic children (2–6 years age) before and after OT. Phase-misalignment was measured by Fourier analysis across a limited bandwidth. Signal-to-noise ratios (SNRs) were estimated from amplitude and phase synchrony in the Fourier domain. Responses were compared to VEPs corrected for phase-misalignment (individual epochs shifted in time to correct for the misalignment). Before OT, amblyopic eyes (AE) had significantly more phase-misalignment, latency prolongation, and lower SNR relative to the fellow eye. Phase-misalignment contributed significantly to low SNR but less so to latency delay in the AE. After OT, phase-alignment improved, SNR improved and latency shortened in the AE. Raw averaged waveforms from the AE improved after OT, primarily at higher spatial frequencies. Correcting for phase-misalignment in the AE sharpened VEP peak responses primarily at low spatial frequencies, but could not account for VEP waveform improvements in the AE after OT at higher spatial frequencies. In summary, VEP abnormalities from the AE are associated with phase-misalignment and reduced SNR possibly related to desynchronization of neuronal activity. The effect of OT on VEP responses is greater than that accounted for by phase-misalignment and SNR alone. [ABSTRACT FROM AUTHOR]

Persons with amblyopia, especially those with strabismus, are known to exhibit abnormal fixational eye movements. In this paper, we compared six characteristics of fixational eye movements among normal control eyes ( n = 16), the non-amblyopic fellow eyes and the amblyopic eyes of anisometropic ( n = 14) and strabismic amblyopes ( n = 14). These characteristics include the frequency, magnitude of landing errors, amplitude and speed of microsaccades, and the amplitude and speed of slow drifts. Fixational eye movements were recorded using retinal imaging while observers monocularly fixated a 1° cross. Eye position data were recovered using a cross-correlation procedure. We found that in general, the characteristics of fixational eye movements are not significantly different between the fellow eyes of amblyopes and controls, and that the strabismic amblyopic eyes are always different from the other groups. Next, we determined the primary factors that limit fixation stability and visual acuity in amblyopic eyes by examining the relative importance of the different oculomotor characteristics, adding acuity (for fixation stability) or fixation stability (for acuity), and the type of amblyopia, as predictive factors in a multiple linear regression model. We show for the first time that the error magnitude of microsaccades, acuity, amplitude and frequency of microsaccades are primary factors limiting fixation stability; while the error magnitude, fixation stability, amplitude of drifts and amplitude of microsaccades are the primary factors limiting acuity. A mediation analysis showed that the effects of error magnitude and amplitude of microsaccades on acuity could be explained, at least in part, by their effects on fixation stability. [ABSTRACT FROM AUTHOR]

Amblyopia is a developmental disorder resulting in poor vision in one eye. The mechanism by which input to the affected eye is prevented from reaching the level of awareness remains poorly understood. We recorded simultaneously from large populations of neurons in the supragranular layers of areas V1 and V2 in 6 macaques that were made amblyopic by rearing with artificial strabismus or anisometropia, and 1 normally reared control. In agreement with previous reports, we found that cortical neuronal signals driven through the amblyopic eyes were reduced, and that cortical neurons were on average more strongly driven by the non-amblyopic than by the amblyopic eyes. We analyzed multiunit recordings using standard population decoding methods, and found that visual signals from the amblyopic eye, while weakened, were not degraded enough to explain the behavioral deficits. Thus additional losses must arise in downstream processing. We tested the idea that under monocular viewing conditions, only signals from neurons dominated by – rather than driven by – the open eye might be used. This reduces the proportion of neuronal signals available from the amblyopic eye, and amplifies the interocular difference observed at the level of single neurons. We conclude that amblyopia might arise in part from degradation in the neuronal signals from the amblyopic eye, and in part from a reduction in the number of signals processed by downstream areas. [ABSTRACT FROM AUTHOR]

There is growing evidence for deficits in motion perception in amblyopia, but these are rarely assessed clinically. In this prospective study we examined the effect of occlusion therapy on motion-defined form perception and multiple-object tracking. Participants included children (3–10 years old) with unilateral anisometropic and/or strabismic amblyopia who were currently undergoing occlusion therapy and age-matched control children with normal vision. At the start of the study, deficits in motion-defined form perception were present in at least one eye in 69% of the children with amblyopia. These deficits were still present at the end of the study in 55% of the amblyopia group. For multiple-object tracking, deficits were present initially in 64% and finally in 55% of the children with amblyopia, even after completion of occlusion therapy. Many of these deficits persisted in spite of an improvement in amblyopic eye visual acuity in response to occlusion therapy. The prevalence of motion perception deficits in amblyopia as well as their resistance to occlusion therapy, support the need for new approaches to amblyopia treatment. [ABSTRACT FROM AUTHOR]

Amblyopia is a neurodevelopmental disorder of vision that arises from disrupted binocular vision during early childhood. Delayed initiation of saccadic eye movements is an established feature of amblyopia. The present study investigated whether oculomotor and/or attentional factors contribute to increased amblyopic eye saccadic latencies. Participants with normal vision (n = 10) and amblyopia (n = 10; 4 anisometropia, 6 strabismic/mixed) performed visually-guided saccades to targets presented via a mirror haploscope. Eye movements were recorded for both eyes even under monocular viewing conditions. In Experiment 1, we measured the latency, amplitude gain and peak velocity of saccades as targets were presented binocularly, or monocularly. Saccadic latencies were significantly longer for both eyes when targets were presented to only the amblyopic eye compared to all other conditions. Saccade gain and main sequence rate constants were similar across groups for all viewing conditions. In Experiment 2, we tested the hypothesis that shifts of overt attention may be deficient when viewing with the amblyopic eye. We presented the fixation target to one eye and the subsequent peripheral target (saccadic error signal) to the other eye. Shifting saccadic targets between the eyes expedited saccadic latencies irrespective of which eye viewed the target in the amblyopia group. These findings indicate that oculomotor factors related to saccade generation are unlikely to be responsible for amblyopic eye saccadic latency delays. We propose that an impairment in the ability to disengage attention from a fixation target and orient to a peripheral target when both targets are seen by the amblyopic eye may contribute to increased saccadic latency. [ABSTRACT FROM AUTHOR]

The notion of a limited, early period of plasticity of the visual system has been challenged by more recent research demonstrating functional enhancement even into adulthood. In amblyopia (“lazy eye”) it is still unclear to what extent the reduced effect of treatment after early childhood is due to declining plasticity or lower compliance with prescribed patching. The aim of this study was to determine the dose–response relationship and treatment efficiency from acuity gain and electronically recorded patching dose rates, and to infer from these parameters on a facet of age dependence of functional plasticity related to occlusion for amblyopia. The Occlusion Dose Monitor was used to record occlusion in 27 participants with previously untreated strabismic and/or anisometropic amblyopia aged between 5.4 and 15.8 (mean 9.2) years during 4 months of conventional treatment. Group data showed improvement of acuity throughout the age span, but significantly more in patients younger than 7 years despite comparable patching dosages. Treatment efficiency declined with age, with the most pronounced effects before the age of 7 years. Thus, electronic recording allowed this first quantitative insight into occlusion treatment spanning the age range from within to beyond the conventional age for patching. Though demonstrating improvement in over 7 year old patients, it confirmed the importance of early detection and treatment of amblyopia. Treatment efficiency is presented as a tool extending insight into age-dependent functional plasticity of the visual system, and providing a basis for comparisons of effects of patching vs. emerging alternative treatment approaches for amblyopia. [ABSTRACT FROM AUTHOR]

Highlights: [•] Speed, spatial and temporal offset affect sensitivity to global motion independently. [•] Amblyopic eye thresholds were higher overall than the other eyes. [•] Amblyopic eye thresholds appear independent of the method used to create motion. [•] Amblyopic eye thresholds appear independent of speed. [ABSTRACT FROM AUTHOR]

Abstract: Amblyopia is a developmental disorder of spatial vision that results from abnormal early visual experience usually due to the presence of strabismus, anisometropia, or both strabismus and anisometropia. Amblyopia results in a range of visual deficits that cannot be corrected by optics because the deficits reflect neural abnormalities. Biological motion refers to the motion patterns of living organisms, and is normally displayed as points of lights positioned at the major joints of the body. In this experiment, our goal was twofold. We wished to examine whether the human visual system in people with amblyopia retained the higher-level processing capabilities to extract visual information from the synchronized actions of others, therefore retaining the ability to detect biological motion. Specifically, we wanted to determine if the synchronized interaction of two agents performing a dancing routine allowed the amblyopic observer to use the actions of one agent to predict the expected actions of a second agent. We also wished to establish whether synchronicity sensitivity (detection of synchronized versus desynchronized interactions) is impaired in amblyopic observers relative to normal observers. The two aims are differentiated in that the first aim looks at whether synchronized actions result in improved expected action predictions while the second aim quantitatively compares synchronicity sensitivity, or the ratio of desynchronized to synchronized detection sensitivities, to determine if there is a difference between normal and amblyopic observers. Our results show that the ability to detect biological motion requires more samples in both eyes of amblyopes than in normal control observers. The increased sample threshold is not the result of low-level losses but may reflect losses in feature integration due to undersampling in the amblyopic visual system. However, like normal observers, amblyopes are more sensitive to synchronized versus desynchronized interactions, indicating that higher-level processing of biological motion remains intact. We also found no impairment in synchronicity sensitivity in the amblyopic visual system relative to the normal visual system. Since there is no impairment in synchronicity sensitivity in either the non-amblyopic or amblyopic eye of amblyopes, our results suggest that the higher order processing of biological motion is intact. [Copyright &y& Elsevier]