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Barry Winn - One of the best experts on this subject based on the ideXlab platform.

  • Contour interaction for high and low contrast optotypes in normal and amblyopic observers
    Ophthalmic and Physiological Optics, 1999
    Co-Authors: Anita J. Simmers, Lyle S. Gray, Paul V Mcgraw, Barry Winn
    Abstract:

    We investigate the influence of stimulus contrast upon contour interaction in normal and amblyopic subjects. Using a computer generated Acuity Task, flanked and unflanked acuities were measured psychometrically at both high contrast (80%) and low contrast (6%), in a group of 19 normal and 11 amblyopic subjects. The crowding ratio for high contrast letters was found to be significantly higher than that for low contrast letters. The extent of the crowding zone was measured at high and low contrast by varying the separation of the optotype and flanking bars. The crowding zone measurement was repeated for the high contrast optotypes using dioptric blur. The position of the flanking contours was found to have a significant effect on letter resolution at high contrast but no significant effect was demonstrable at low contrast. With the addition of dioptric blur the effect of contour interaction became negligible at high contrast. These findings support the hypothesis that the crowding effect is: (1) similar in normal and amblyopic eyes when tested at threshold; (2) is contrast dependent appearing only for high contrast optotypes.

  • contour interaction for high and low contrast optotypes in normal and amblyopic observers
    Ophthalmic and Physiological Optics, 1999
    Co-Authors: Anita J. Simmers, Lyle S. Gray, Paul V Mcgraw, Barry Winn
    Abstract:

    Summary We investigate the influence of stimulus contrast upon contour interaction in normal and amblyopic subjects. Using a computer generated Acuity Task, flanked and unflanked acuities were measured psychometrically at both high contrast (80%) and low contrast (6%), in a group of 19 normal and 11 amblyopic subjects. The crowding ratio for high contrast letters was found to be significantly higher than that for low contrast letters. The extent of the crowding zone was measured at high and low contrast by varying the separation of the optotype and flanking bars. The crowding zone measurement was repeated for the high contrast optotypes using dioptric blur. The position of the flanking contours was found to have a significant effect on letter resolution at high contrast but no significant effect was demonstrable at low contrast. With the addition of dioptric blur the effect of contour interaction became negligible at high contrast. These findings support the hypothesis that the crowding effect is: (1) similar in normal and amblyopic eyes when tested at threshold; (2) is contrast dependent appearing only for high contrast optotypes. # 1999 The College of Optometrists. Published by Elsevier Science Ltd. All rights reserved

Anita J. Simmers - One of the best experts on this subject based on the ideXlab platform.

  • Contour interaction for high and low contrast optotypes in normal and amblyopic observers
    Ophthalmic and Physiological Optics, 1999
    Co-Authors: Anita J. Simmers, Lyle S. Gray, Paul V Mcgraw, Barry Winn
    Abstract:

    We investigate the influence of stimulus contrast upon contour interaction in normal and amblyopic subjects. Using a computer generated Acuity Task, flanked and unflanked acuities were measured psychometrically at both high contrast (80%) and low contrast (6%), in a group of 19 normal and 11 amblyopic subjects. The crowding ratio for high contrast letters was found to be significantly higher than that for low contrast letters. The extent of the crowding zone was measured at high and low contrast by varying the separation of the optotype and flanking bars. The crowding zone measurement was repeated for the high contrast optotypes using dioptric blur. The position of the flanking contours was found to have a significant effect on letter resolution at high contrast but no significant effect was demonstrable at low contrast. With the addition of dioptric blur the effect of contour interaction became negligible at high contrast. These findings support the hypothesis that the crowding effect is: (1) similar in normal and amblyopic eyes when tested at threshold; (2) is contrast dependent appearing only for high contrast optotypes.

  • contour interaction for high and low contrast optotypes in normal and amblyopic observers
    Ophthalmic and Physiological Optics, 1999
    Co-Authors: Anita J. Simmers, Lyle S. Gray, Paul V Mcgraw, Barry Winn
    Abstract:

    Summary We investigate the influence of stimulus contrast upon contour interaction in normal and amblyopic subjects. Using a computer generated Acuity Task, flanked and unflanked acuities were measured psychometrically at both high contrast (80%) and low contrast (6%), in a group of 19 normal and 11 amblyopic subjects. The crowding ratio for high contrast letters was found to be significantly higher than that for low contrast letters. The extent of the crowding zone was measured at high and low contrast by varying the separation of the optotype and flanking bars. The crowding zone measurement was repeated for the high contrast optotypes using dioptric blur. The position of the flanking contours was found to have a significant effect on letter resolution at high contrast but no significant effect was demonstrable at low contrast. With the addition of dioptric blur the effect of contour interaction became negligible at high contrast. These findings support the hypothesis that the crowding effect is: (1) similar in normal and amblyopic eyes when tested at threshold; (2) is contrast dependent appearing only for high contrast optotypes. # 1999 The College of Optometrists. Published by Elsevier Science Ltd. All rights reserved

Lyle S. Gray - One of the best experts on this subject based on the ideXlab platform.

  • Contour interaction for high and low contrast optotypes in normal and amblyopic observers
    Ophthalmic and Physiological Optics, 1999
    Co-Authors: Anita J. Simmers, Lyle S. Gray, Paul V Mcgraw, Barry Winn
    Abstract:

    We investigate the influence of stimulus contrast upon contour interaction in normal and amblyopic subjects. Using a computer generated Acuity Task, flanked and unflanked acuities were measured psychometrically at both high contrast (80%) and low contrast (6%), in a group of 19 normal and 11 amblyopic subjects. The crowding ratio for high contrast letters was found to be significantly higher than that for low contrast letters. The extent of the crowding zone was measured at high and low contrast by varying the separation of the optotype and flanking bars. The crowding zone measurement was repeated for the high contrast optotypes using dioptric blur. The position of the flanking contours was found to have a significant effect on letter resolution at high contrast but no significant effect was demonstrable at low contrast. With the addition of dioptric blur the effect of contour interaction became negligible at high contrast. These findings support the hypothesis that the crowding effect is: (1) similar in normal and amblyopic eyes when tested at threshold; (2) is contrast dependent appearing only for high contrast optotypes.

  • contour interaction for high and low contrast optotypes in normal and amblyopic observers
    Ophthalmic and Physiological Optics, 1999
    Co-Authors: Anita J. Simmers, Lyle S. Gray, Paul V Mcgraw, Barry Winn
    Abstract:

    Summary We investigate the influence of stimulus contrast upon contour interaction in normal and amblyopic subjects. Using a computer generated Acuity Task, flanked and unflanked acuities were measured psychometrically at both high contrast (80%) and low contrast (6%), in a group of 19 normal and 11 amblyopic subjects. The crowding ratio for high contrast letters was found to be significantly higher than that for low contrast letters. The extent of the crowding zone was measured at high and low contrast by varying the separation of the optotype and flanking bars. The crowding zone measurement was repeated for the high contrast optotypes using dioptric blur. The position of the flanking contours was found to have a significant effect on letter resolution at high contrast but no significant effect was demonstrable at low contrast. With the addition of dioptric blur the effect of contour interaction became negligible at high contrast. These findings support the hypothesis that the crowding effect is: (1) similar in normal and amblyopic eyes when tested at threshold; (2) is contrast dependent appearing only for high contrast optotypes. # 1999 The College of Optometrists. Published by Elsevier Science Ltd. All rights reserved

Paul V Mcgraw - One of the best experts on this subject based on the ideXlab platform.

  • Contour interaction for high and low contrast optotypes in normal and amblyopic observers
    Ophthalmic and Physiological Optics, 1999
    Co-Authors: Anita J. Simmers, Lyle S. Gray, Paul V Mcgraw, Barry Winn
    Abstract:

    We investigate the influence of stimulus contrast upon contour interaction in normal and amblyopic subjects. Using a computer generated Acuity Task, flanked and unflanked acuities were measured psychometrically at both high contrast (80%) and low contrast (6%), in a group of 19 normal and 11 amblyopic subjects. The crowding ratio for high contrast letters was found to be significantly higher than that for low contrast letters. The extent of the crowding zone was measured at high and low contrast by varying the separation of the optotype and flanking bars. The crowding zone measurement was repeated for the high contrast optotypes using dioptric blur. The position of the flanking contours was found to have a significant effect on letter resolution at high contrast but no significant effect was demonstrable at low contrast. With the addition of dioptric blur the effect of contour interaction became negligible at high contrast. These findings support the hypothesis that the crowding effect is: (1) similar in normal and amblyopic eyes when tested at threshold; (2) is contrast dependent appearing only for high contrast optotypes.

  • contour interaction for high and low contrast optotypes in normal and amblyopic observers
    Ophthalmic and Physiological Optics, 1999
    Co-Authors: Anita J. Simmers, Lyle S. Gray, Paul V Mcgraw, Barry Winn
    Abstract:

    Summary We investigate the influence of stimulus contrast upon contour interaction in normal and amblyopic subjects. Using a computer generated Acuity Task, flanked and unflanked acuities were measured psychometrically at both high contrast (80%) and low contrast (6%), in a group of 19 normal and 11 amblyopic subjects. The crowding ratio for high contrast letters was found to be significantly higher than that for low contrast letters. The extent of the crowding zone was measured at high and low contrast by varying the separation of the optotype and flanking bars. The crowding zone measurement was repeated for the high contrast optotypes using dioptric blur. The position of the flanking contours was found to have a significant effect on letter resolution at high contrast but no significant effect was demonstrable at low contrast. With the addition of dioptric blur the effect of contour interaction became negligible at high contrast. These findings support the hypothesis that the crowding effect is: (1) similar in normal and amblyopic eyes when tested at threshold; (2) is contrast dependent appearing only for high contrast optotypes. # 1999 The College of Optometrists. Published by Elsevier Science Ltd. All rights reserved

Catherine M Suttle - One of the best experts on this subject based on the ideXlab platform.

  • the development of crowding and interocular interactions in a resolution Acuity Task
    Investigative Ophthalmology & Visual Science, 2011
    Co-Authors: Ximena Masgoret, Lisa Asper, Jack Alexander, Catherine M Suttle
    Abstract:

    Purpose.: To investigate the impact of interocular similarities of a surround stimulus on foveal resolution Acuity in the normally developing visual system. Methods.: Liquid crystal shutter goggles synchronized with the monitor frame rate were used to present a Landolt C and surround bars to one or both eyes, in monocular, dichoptic, half-binocular, and binocular viewing conditions. Resolution Acuity was measured under each condition in 56 normally sighted children (7 to 14 years of age) and 22 adults (21 to 38 years of age). The effect of the surround bars (crowding) was tested in a subgroup of nine children, and 10 adults. Results.: Across all age groups resolution Acuity was significantly better in the binocular condition than in the other three viewing conditions (binocular summation), and was significantly better in the half-binocular (with target presented to the test eye and bars presented to both eyes) than in the dichoptic condition (target presented to test eye and bars presented to the nontested eye only). In children, but not in adults, resolution Acuity was significantly better without than with bars. Conclusions.: The interocular similarities may explain the better visual resolution in the half-binocular condition than in the dichoptic condition for all age groups tested. The results suggest that interocular interactions underpinning resolution Acuity under these viewing conditions are developed in early childhood. The foveal crowding effect was found to be apparent at the beginning of school age, and diminished with maturation.