December 2002
Volume 43, Issue 13
ARVO Annual Meeting Abstract  |   December 2002
Amblyopes can Combine Orientation Across Space
Author Affiliations & Notes
  • B Mansouri
    Ophthalmology & Vis Sci McGill University Montréal PQ Canada
  • HA Allen
    Ophthalmology & Vis Sci McGill University Montréal PQ Canada
  • O Ehrt
    Ophthalmology & Vis Sci McGill University Montréal PQ Canada
  • SC Dakin
    Institute of Ophthalmology University College London United Kingdom
  • RF Hess
    Ophthalmology & Vis Sci McGill University Montréal PQ Canada
  • Footnotes
    Commercial Relationships   B. Mansouri, None; H.A. Allen, None; O. Ehrt, None; S.C. Dakin, None; R.F. Hess, None. Grant Identification: Canadian Institutes of Health Research: MOP 10818
Investigative Ophthalmology & Visual Science December 2002, Vol.43, 3935. doi:
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    • Get Citation

      B Mansouri, HA Allen, O Ehrt, SC Dakin, RF Hess; Amblyopes can Combine Orientation Across Space . Invest. Ophthalmol. Vis. Sci. 2002;43(13):3935.

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

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Abstract: : Purpose: Normal human subjects are able to discriminate the mean orientation of arrays of orientated Gabors, even when there is considerable orientation variability in the array. It is possible that amblyopic subjects are poor at global orientation discrimination due to either a raised level of internal noise or reduced sampling efficiency. To address this problem we used the paradigm of the Dakin (JOSA A, 18, 2001) to compare the internal noise and sampling efficiency in the normal and amblyopic eyes of amblyopic subjects. Methods: Sixteen luminance defined Gabor patches were randomly distributed in the central 15 deg visual field and were presented to amblyopic subjects. The range of the orientations present in any one array varied from 0 - 32 deg and subjects had to discriminate whether the mean orientation was tilted to the left or right of vertical. Global orientation discrimination thresholds for the normal and amblyopic eyes were measured after adjusting the contrast of patches for equal orientation discriminability with a single Gabor patch. Estimates for internal noise and number of samples were derived from summation-variance model fits to the data. Results: Visual acuity of the amblyopic eyes of 5 subjects varied from 20/200 to 20/40. Orientation discrimination thresholds increased when orientation variance was larger than 4 deg. The thresholds from the amblyopic and normal eyes were similar. The number of samples used did not decrease for the amblyopic eye. Internal noise and number of samples were slightly increased. Conclusion: Amblyopes are able to integrate the orientation information across space when using their amblyopic eyes similar to their normal eye. The sampling ability as gauged by this particular task appears normal in amblyopia.

Keywords: 313 amblyopia • 579 shape, form, contour, object perception • 586 spatial vision 

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