Involvement of target contrast in visual masking location tasks deficients in myopia

Kuo, Hui-Ying, Schmid, Katrina L., & Atchison, David A. (2009) Involvement of target contrast in visual masking location tasks deficients in myopia. In Proceedings of the 12th Biennial Scientific and Educators' Meeting in Optometry, Optometrists Association Australia, University of Auckland, Auckland.

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Purpose: There have been few studies of visual temporal processing of myopic eyes. This study investigated the visual performance of emmetropic and myopic eyes using a backward visual masking location task. Methods: Data were collected for 39 subjects (15 emmetropes, 12 stable myopes, 12 progressing myopes). In backward visual masking, a target’s visibility is reduced by a mask presented in quick succession ‘after’ the target. The target and mask stimuli were presented at different interstimulus intervals (from 12 to 300 ms). The task involved locating the position of a target letter with both a higher (seven per cent) and a lower (five per cent) contrast. Results: Emmetropic subjects had significantly better performance for the lower contrast location task than the myopes (F2,36 = 22.88; p < 0.001) but there was no difference between the progressing and stable myopic groups (p = 0.911). There were no differences between the groups for the higher contrast location task (F2,36 = 0.72, p = 0.495). No relationship between task performance and either the magnitude of myopia or axial length was found for either task. Conclusions: A location task deficit was observed in myopes only for lower contrast stimuli. Both emmetropic and myopic groups had better performance for the higher contrast task compared to the lower contrast task, with myopes showing considerable improvement. This suggests that five per cent contrast may be the contrast threshold required to bias the task towards the magnocellular system (where myopes have a temporal processing deficit). Alternatively, the task may be sensitive to the contrast sensitivity of the observer.

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ID Code: 31480
Item Type: Conference Paper
Refereed: Yes
Additional Information: The abstract of this paper was published in "Clinical and Experimental Optometry", Vol. 92, no. 1, pp.51-69. [please see DOI].
DOI: 10.1111/j.1444-0938.2008.00341.x
Divisions: Current > QUT Faculties and Divisions > Faculty of Health
Current > Institutes > Institute of Health and Biomedical Innovation
Current > Schools > School of Optometry & Vision Science
Deposited On: 24 Mar 2010 21:29
Last Modified: 21 Apr 2010 17:02

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