Contrast masking in strabismic amblyopia: attenuation, noise, interocular suppression and binocular summation


To investigate amblyopic contrast vision at threshold and above we performed pedestal-masking (contrastdiscrimination) experiments with a group of eight strabismic amblyopes using horizontal sinusoidal gratings (mainly 3 c/deg) in monocular, binocular and dichoptic configurations balanced across eye (i.e. five conditions). With some exceptions in some observers, the four main results were as follows. (1) For the monocular and dichoptic conditions, sensitivity was less in the amblyopic eye than in the good eye at all mask contrasts. (2) Binocular and monocular dipper functions superimposed in the good eye. (3) Monocular masking functions had a normal dipper shape in the good eye, but facilitation was diminished in the amblyopic eye. (4) A less consistent result was normal facilitation in dichoptic masking when testing the good eye, but a loss of this when testing the amblyopic eye. This pattern of amblyopic results was replicated in a normal observer by placing a neutral density filter in front of one eye. The two-stage model of binocular contrast gain control [Meese, T.S., Georgeson, M.A. & Baker, D.H. (2006). Binocular contrast vision at and above threshold. Journal of Vision 6, 1224--1243.] was `lesioned' in several ways to assess the form of the amblyopic deficit. The most successful model involves attenuation of signal and an increase in noise in the amblyopic eye, and intact stages of interocular suppression and binocular summation. This implies a behavioural influence from monocular noise in the amblyopic visual system as well as in normal observers with an ND filter over one eye.

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Divisions: College of Health & Life Sciences > School of Optometry > Optometry
College of Health & Life Sciences > Clinical and Systems Neuroscience
College of Health & Life Sciences > School of Optometry > Centre for Vision and Hearing Research
Additional Information: NOTICE: this is the author’s version of a work that was accepted for publication in Vision Research. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Baker, Daniel H.; Meese, Timothy S. and Hess, Robert F. (2008). Contrast masking in strabismic amblyopia: attenuation, noise, interocular suppression and binocular summation. Vision Research, 48 (15), pp. 1625-1640. DOI 10.1016/j.visres.2008.04.017
Uncontrolled Keywords: human vision,amblyopia,strabismus,masking,contrast discrimination,noise,Ophthalmology,Sensory Systems
Publication ISSN: 1878-5646
Last Modified: 22 May 2024 07:08
Date Deposited: 11 Mar 2019 17:48
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Related URLs: http://www.scop ... tnerID=8YFLogxK (Scopus URL)
PURE Output Type: Article
Published Date: 2008-06-10
Authors: Baker, Daniel H.
Meese, Timothy S. (ORCID Profile 0000-0003-3744-4679)
Hess, Robert F.


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