October 2016
Volume 57, Issue 13
Open Access
Research Highlight  |   October 2016
Amblyopic Perceptual Suppression Revealed
Author Affiliations
  • Janine D. Mendola
    McGill Vision Research, Ophthalmology Department, McGill University, Montreal, Quebec, Canada; janine.mendola@mcgill.ca
Investigative Ophthalmology & Visual Science October 2016, Vol.57, 5655. doi:10.1167/iovs.16-20851
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      Janine D. Mendola; Amblyopic Perceptual Suppression Revealed. Invest. Ophthalmol. Vis. Sci. 2016;57(13):5655. doi: 10.1167/iovs.16-20851.

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      © ARVO (1962-2015); The Authors (2016-present)

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In this issue, Birch and colleagues1 publish a notable paper entitled “Assessing Suppression in Amblyopic Children with a Dichoptic Eye Chart.” These novel experiments combine well-considered basic science and timely clinical relevance. This is a behavioral study of a large sample of children with amblyopia of multiple etiologies. The experiments were strategically developed to fill a gap in pediatric amblyopia assessment and treatment. The etiological and functional role of interocular suppression in adults with amblyopia has been an area of important focus in recent years.2,3 Extending these models to children is significant theoretically and practically. Child-friendly tests that parametrically vary the degree of suppression are lacking, and hence one is reported here. The authors find that children with either anisometropic or strabismic amblyopia require letters in the weak eye with far more contrast (up to 5 times) than coincident letters in the fellow eye to achieve symmetrical (50%) reports. These children have highly asymmetrical interocular suppression that can vary in severity. This quantitative index correlated with baseline visual acuity, and improved in tandem with acuity after treatment. The association between good acuity and low suppression harmonizes with recent adult data, but contrasts with an older view that posited strong suppression to be a by-product of achieving good acuity. Instead, new binocular treatments for amblyopia are showing success in improving acuity, and depth perception, by reducing suppression.4 The recent treatment success in adults highlights that latent potential for binocular integration remains in maturity. The potential benefit may be even greater if started early, and the current results suggest this new test is sensitive and feasible as young as 3 years of age. The specific neural mechanisms altered by suppression treatment are not yet fully identified5 but we can likely look forward to progress on that basic science question possibly using similar techniques. 
References
Birch EE, Morale SE, Jost RM, et al. Assessing suppression in amblyopic children with a dichoptic eye chart. Invest Ophthalmol Vis Sci. 2016; 57: 5649–5654.
McKee SP, Levi DM, Movshon JA. The pattern of visual deficits in amblyopia. J Vis. 2003; 3 (5): 380–405.
Mansouri B, Thompson B, Hess RF. Measurement of suprathreshold binocular interactions in amblyopia. Vision Res. 2008; 48: 2775–2784.
Hess RF, Thompson B. Amblyopia and the binocular approach to its therapy. Vision Res. 2015; 114: 4–16.
Conner IP, Odom JV, Schwartz TL, Mendola JD. Retinotopic maps and foveal suppression in the visual cortex of amblyopic adults. J Physiol. 2007; 583 (pt 1): 159–173.
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