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Richard Hollingsworth, Amanda Ludlow, Arnold Wilkins, Peter M Allen, Richard Calver; Frequency doubling perimetry and random dot kinematograms in deaf and hearing children. Invest. Ophthalmol. Vis. Sci. 2014;55(13):168.
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© ARVO (1962-2015); The Authors (2016-present)
The difficulty that deaf children have in learning to read has generally been attributed to phonological deficits, but their visual deficits may also contribute. In hearing children reading difficulty has been associated with magnocellular dysfunction. Here we investigate magnocelluar function in deaf children using two psychophysical tasks.
Thirty four children (18 deaf and 16 hearing (mean age 14+2.1) were recruited from a school for the deaf and an associated main stream secondary school in Derby UK. Recruitment conformed to the Helsinki declaration and received Anglia Ruskin University ethical approval. The children were assessed using the 10 Intuitive colour Overlays and 7 (38%) of the deaf participants chose a yellow overlay. Magnocellular function was investigated with: 1)A Humphrey visual field analyser using frequency doubling technology (FDT). Thresholds were assessed at 17 retinal locations within the central 20 degrees .The central location was tested with a 5 degrees diameter circle and all other locations were 10 degree squares. The habitual optical correction was worn while each eye was tested separately in turn, right then left 2)Random dot kinematograms (RDK) were viewed binocularly at 0.75m on a 467mm LCD screen. Two circular patches subtending 7 degrees consisting of 150 high luminance dots had a horizontal separation of 4 degrees. Both patches were presented simultaneously for 300ms. One patch had dots which moved with Brownian motion whilst in the other patch 5-90% of dots moved coherently to the left or right. The coherent dots were presented on the left or right patch at random and the participant clicked either left or right mouse buttons to indicate which patch contained the coherent dots. A Quest procedure was used to obtain a threshold.
: In certain retinal regions FDT revealed a significant difference between the deaf participants who chose a yellow overlay and the remaining participants, including those in the deaf and hearing groups. (p= 0.02) . RDK showed no significance between the deaf and hearing groups (p=0.96).
The FDT findings are consistent with a possible magnocellular dysfunction in some of the deaf participants. although the RDK task did not reveal any deficits.
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