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R.C. St John; Cross–callosal transmission associated with Strabismus: 4 methods of assessment compared. . Invest. Ophthalmol. Vis. Sci. 2004;45(13):2547.
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Purpose: Both psychophysical and anatomical studies have shown that strabismus resulting in amblyopia affects the normal development of fibers within the posterior corpus callosum. This study examined the reliability and accuracy of transfer of information between the two cerebral hemispheres via the corpus callosum in human strabismic and non–strabismic subjects using different methodologies. Methods: Ten strabismic amblyopes and 10 control subjects were examined using 4 common methods of assessing cross callosal transmission. This involved using, manual response times, vocal response times, judgements of visual target onset precedence, and two alternative forced choice psychophysical estimates the relative size, position, and width of stimuli presented in the left or right visual fields. Results: Just Noticeable Differences in the strabismic group were significantly greater only when the judgments required cross–callosal transmission of information. In the normal control group there were no differences between the two conditions. Data from the reaction time, and target onset procedures also indicated longer overall cross–callosal transmission times only for the strabismic subjects. The findings were consistent within strabismic subjects across these three procedures. Vocal response times proved to be unreliable as estimates of interhemispheric transmission time for either group. Conclusions:Strabismus with amblyopia may result in slowed and/or abnormal cross–callosal transmission of visual information. This finding supports numerous anatomical and electrophysiological studies on strabismus, and suggests an abnormal development of the posterior corpus callosum in early life.
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