A Binocular Approach to Treating Amblyopia: Antisuppression Therapy
We developed a binocular treatment for amblyopia based on antisuppression therapy.
A novel procedure is outlined for measuring the extent to which the fixing eye suppresses the fellow amblyopic eye. We hypothesize that suppression renders a structurally binocular system, functionally monocular.
We demonstrate using three strabismic amblyopes that information can be combined normally between their eyes under viewing conditions where suppression is reduced. Also, we show that prolonged periods of viewing (under the artificial conditions of stimuli of different contrast in each eye) during which information from the two eyes is combined leads to a strengthening of binocular vision in such cases and eventual combination of binocular information under natural viewing conditions (stimuli of the same contrast in each eye). Concomitant improvement in monocular acuity of the amblyopic eye occurs with this reduction in suppression and strengthening of binocular fusion. Furthermore, in each of the three cases, stereoscopic function is established.
This provides the basis for a new treatment of amblyopia, one that is purely binocular and aimed at reducing suppression as a first step.
Available from: Chantal Milleret
- "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.
Available from: Herb Goltz
- "Importantly, these deficits are not only present during amblyopic eye viewing; they are also evident to a lesser extent, during binocular and fellow eye viewing , , . It is generally agreed that the earliest functional and anatomical abnormalities that contribute significantly to the behavioural losses in amblyopia occur in cortical area V1 , ,  (see also the role of LGN in the feedback pathway , , ). These abnormalities are then amplified downstream in the extrastriate cortex and specialized cortical areas , , , , . "
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ABSTRACT: Impairment of spatiotemporal visual processing in amblyopia has been studied extensively, but its effects on visuomotor tasks have rarely been examined. Here, we investigate how visual deficits in amblyopia affect motor planning and online control of visually-guided, unconstrained reaching movements.
Thirteen patients with mild amblyopia, 13 with severe amblyopia and 13 visually-normal participants were recruited. Participants reached and touched a visual target during binocular and monocular viewing. Motor planning was assessed by examining spatial variability of the trajectory at 50-100 ms after movement onset. Online control was assessed by examining the endpoint variability and by calculating the coefficient of determination (R(2)) which correlates the spatial position of the limb during the movement to endpoint position.
Patients with amblyopia had reduced precision of the motor plan in all viewing conditions as evidenced by increased variability of the reach early in the trajectory. Endpoint precision was comparable between patients with mild amblyopia and control participants. Patients with severe amblyopia had reduced endpoint precision along azimuth and elevation during amblyopic eye viewing only, and along the depth axis in all viewing conditions. In addition, they had significantly higher R(2) values at 70% of movement time along the elevation and depth axes during amblyopic eye viewing.
Sensory uncertainty due to amblyopia leads to reduced precision of the motor plan. The ability to implement online corrections depends on the severity of the visual deficit, viewing condition, and the axis of the reaching movement. Patients with mild amblyopia used online control effectively to compensate for the reduced precision of the motor plan. In contrast, patients with severe amblyopia were not able to use online control as effectively to amend the limb trajectory especially along the depth axis, which could be due to their abnormal stereopsis.
Available from: Ali Rastegarpour
- "Although the anaglyphic system could potentially serve as an alternative to VR-based systems by accomplishing the same objectives, the evidence supporting VR-based systems as a therapeutic intervention is limited, and the only available studies including clinical data in this regard are two case series reporting the short-term outcomes in six and twelve patients, respectively.3,17 Computer-based active vision therapy has received much attention for amblyopia and one of the recent publications by Hess et al,18 demonstrating success for active vision therapy in three amblyopic patients. However, there is still not much evidence in the literature to support most modalities. "
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ABSTRACT: Virtual reality (VR)-based treatment has been introduced as a potential option for amblyopia management, presumably without involving the problems of occlusion and penalization, including variable and unsatisfactory outcomes, long duration of treatment, poor compliance, psychological impact, and complications. However, VR-based treatment is costly and not accessible for most children. This paper introduces a method that encompasses the advantages of VR-based treatment at a lower cost.
The presented system consists of a pair of glasses with two color filters and software for use on a personal computer. The software is designed such that some active graphic components can only be seen by the amblyopic eye and are filtered out for the other eye. Some components would be seen by both to encourage fusion. The result is that the patient must use both eyes, and specifically the amblyopic eye, to play the games.
A prototype of the system, the ABG InSight, was found capable of successfully filtering out elements of a certain color and therefore, could prove to be a viable alternative to VR-based treatment for amblyopia.
The anaglyphic system maintains most of the advantages of VR-based systems, but is less costly and highly accessible. It fulfills the means that VR-based systems are designed to achieve, and warrants further investigation.
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