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

Contrast masking in strabismic amblyopia: attenuation, noise, interocular suppression and binocular summation
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 (contrast discrimination) 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.
human vision, amblyopia, strabismus, masking, contrast discrimination, noise
0042-6989
1625-1640
Baker, Daniel H.
92545fbf-bb42-4155-a530-91b917648047
Meese, Tim S.
0c8c57a5-1341-42d6-be91-cac46c6d6f34
Hess, Robert F.
e68cedd8-a5a6-4ece-aade-c017b1fb1d21
Baker, Daniel H.
92545fbf-bb42-4155-a530-91b917648047
Meese, Tim S.
0c8c57a5-1341-42d6-be91-cac46c6d6f34
Hess, Robert F.
e68cedd8-a5a6-4ece-aade-c017b1fb1d21

Baker, Daniel H., Meese, Tim S. and Hess, Robert F. (2008) Contrast masking in strabismic amblyopia: attenuation, noise, interocular suppression and binocular summation. Vision Research, 48 (15), 1625-1640. (doi:10.1016/j.visres.2008.04.017).

Record type: Article

Abstract

To investigate amblyopic contrast vision at threshold and above we performed pedestal-masking (contrast discrimination) 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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More information

Submitted date: 14 February 2008
Published date: 10 July 2008
Keywords: human vision, amblyopia, strabismus, masking, contrast discrimination, noise

Identifiers

Local EPrints ID: 52412
URI: https://eprints.soton.ac.uk/id/eprint/52412
ISSN: 0042-6989
PURE UUID: 72ff2652-8b30-4b49-9e10-8db20238fe95

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Date deposited: 26 Jun 2008
Last modified: 13 Mar 2019 20:42

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