Measurement of suprathreshold binocular interactions in amblyopia

McGill Vision Research, Department of Ophthalmology, McGill University, 687 Pine Ave W (H4-14), Montreal, Que., Canada PQ H3A 1A1.
Vision research (Impact Factor: 1.82). 09/2008; 48(28):2775-84. DOI: 10.1016/j.visres.2008.09.002
Source: PubMed


It has been established that in amblyopia, information from the amblyopic eye (AME) is not combined with that from the fellow fixing eye (FFE) under conditions of binocular viewing. However, recent evidence suggests that mechanisms that combine information between the eyes are intact in amblyopia. The lack of binocular function is most likely due to the imbalanced inputs from the two eyes under binocular conditions [Baker, D. H., Meese, T. S., Mansouri, B., & Hess, R. F. (2007b). Binocular summation of contrast remains intact in strabismic amblyopia. Investigative Ophthalmology & Visual Science, 48(11), 5332-5338]. We have measured the extent to which the information presented to each eye needs to differ for binocular combination to occur and in doing so we quantify the influence of interocular suppression. We quantify these suppressive effects for suprathreshold processing of global stimuli for both motion and spatial tasks. The results confirm the general importance of these suppressive effects in rendering the structurally binocular visual system of a strabismic amblyope, functionally monocular.

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Available from: Benjamin Thompson, May 14, 2015
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    • "This is the reason why new strategies implicating binocular stimulations are presently being developed to treat amblyopia and binocular vision loss in strabismic (and anisometropic) subjects. Hess and his colleagues are among the most active in that field, with their strategy to suppress interocular suppression in order to recover acuity by the amblyopic eye and 3D perception (Baker et al., 2007; Mansouri et al., 2008; Hess et al., 2010a,b, 2011; Zhou et al., 2012 cf. also Hess et al., 2014 for review). For that, they have developed dichoptic devices that allow a binocular stimulation with different images in each eye, the combination of which is stereoscopic. "
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    ABSTRACT: Strabismus is a frequent ocular disorder that develops early in life in humans. As a general rule, it is characterized by a misalignment of the visual axes which most often appears during the critical period of visual development. However other characteristics of strabismus may vary greatly among subjects, for example, being convergent or divergent, horizontal or vertical, with variable angles of deviation. Binocular vision may also vary greatly. Our main goal here is to develop the idea that such "polymorphy" reflects a wide variety in the possible origins of strabismus. We propose that strabismus must be considered as possibly resulting from abnormal genetic and/or acquired factors, anatomical and/or functional abnormalities, in the sensory and/or the motor systems, both peripherally and/or in the brain itself. We shall particularly develop the possible "central" origins of strabismus. Indeed, we are convinced that it is time now to open this "black box" in order to move forward. All of this will be developed on the basis of both presently available data in literature (including most recent data) and our own experience. Both data in biology and medicine will be referred to. Our conclusions will hopefully help ophthalmologists to better understand strabismus and to develop new therapeutic strategies in the future. Presently, physicians eliminate or limit the negative effects of such pathology both on the development of the visual system and visual perception through the use of optical correction and, in some cases, extraocular muscle surgery. To better circumscribe the problem of the origins of strabismus, including at a cerebral level, may improve its management, in particular with respect to binocular vision, through innovating tools by treating the pathology at the source.
    Frontiers in Integrative Neuroscience 09/2014; 8:71. DOI:10.3389/fnint.2014.00071
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    • "Experimental models of patching therapy for amblyopia applied to animals rendered amblyopic by a prior period of early MD indicate that the benefits of a patching therapy can be heightened when combined with critical amounts of binocular visual input each day (Mitchell and Sengpiel, 2009). Recent studies (Baker et al., 2007; Mansouri et al., 2008; Vedamurthy et al., 2008) provided new information on how signals from the amblyopic and not amblyopic eyes can impact on each other and on binocular vision (see also Mitchell and Duffy, 2014 for a recent review). "
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    ABSTRACT: Amblyopia is the most common form of impairment of visual function affecting one eye, with a prevalence of about 1-5% of the total world population. Amblyopia usually derives from conditions of early functional imbalance between the two eyes, owing to anisometropia, strabismus, or congenital cataract, and results in a pronounced reduction of visual acuity and severe deficits in contrast sensitivity and stereopsis. It is widely accepted that, due to a lack of sufficient plasticity in the adult brain, amblyopia becomes untreatable after the closure of the critical period in the primary visual cortex. However, recent results obtained both in animal models and in clinical trials have challenged this view, unmasking a previously unsuspected potential for promoting recovery even in adulthood. In this context, non invasive procedures based on visual perceptual learning, i.e., the improvement in visual performance on a variety of simple visual tasks following practice, emerge as particularly promising to rescue discrimination abilities in adult amblyopic subjects. This review will survey recent work regarding the impact of visual perceptual learning on amblyopia, with a special focus on a new experimental model of perceptual learning in the amblyopic rat.
    Frontiers in Neural Circuits 07/2014; 8:82. DOI:10.3389/fncir.2014.00082 · 3.60 Impact Factor
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    • "It appears that deprivation itself impairs spatial vision, but that competition between the eyes in unilateral cases results in additional deficits for the amblyopic eye (Birch et al., 1998). A strong case has been made that suppression of the weaker by the stronger eye plays an important role in the local spatial losses associated with unilateral strabismic and anisometropic amblyopia (Mansouri et al., 2008; Li et al., 2011; Wong, 2011). However, impaired binocular interactions appear to have some role to play in bilateral cases as well. "
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    ABSTRACT: Amblyopia is a neurodevelopmental disorder of the visual system that is associated with disrupted binocular vision during early childhood. There is evidence that the effects of amblyopia extend beyond the primary visual cortex to regions of the dorsal and ventral extra-striate visual cortex involved in visual integration. Here, we review the current literature on global processing deficits in observers with either strabismic, anisometropic, or deprivation amblyopia. A range of global processing tasks have been used to investigate the extent of the cortical deficit in amblyopia including: global motion perception, global form perception, face perception, and biological motion. These tasks appear to be differentially affected by amblyopia. In general, observers with unilateral amblyopia appear to show deficits for local spatial processing and global tasks that require the segregation of signal from noise. In bilateral cases, the global processing deficits are exaggerated, and appear to extend to specialized perceptual systems such as those involved in face processing.
    Frontiers in Psychology 06/2014; 5:583. DOI:10.3389/fpsyg.2014.00583 · 2.80 Impact Factor
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