An investigation of the contrast sensitivity in dyslexic children

Document Type : Original article

Authors

1 1. Student Reseach Committee, MSc Student of Optometry, Faculty of Rehabilitation Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran.

2 2. OD in Optometry, Faculty of Rehabilitation Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran.

3 3. Professor of Ophthalmology, Faculty of Rehabilitation Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran.

4 4. MSc in Psychology and Education of Exceptional Children, Office of Special Education.

5 5. MSc in Biostatistics, Faculty of Rehabilitation, Shahid Beheshti University of Medical Sciences, Tehran, Iran

Abstract

Background and Aim: A review of the neurophysiological studies suggests that dyslexia is the result of a deficit in the magnocellular part of the visual system. Most of the evidence cited in favour of this hypothesis is from contrast sensitivity studies. This study tested the hypothesis that visual processing deficits may be present in dyslexia by comparing the visual contrast sensitivity of dyslexic children and controls.
Materials and Methods: contrast thresholds were recorded in 67 children, 26 dyslexic (mean age of 8.76±1.33) and 41 control group (mean age 9.07±1.40). Contrast sensitivity was measured using Freiburg acuity and contrast test (FrACT) version 3.7 at frequency 5cpd in both eyes. The results were then analyzed using SPSS-18.
Results: mean contrast threshold of Right eyes in dyslexic group(0.62±0.12)and control group (0.68± 0.15), mean contrast threshold of Left eyes in dyslexic group (0.61±0.16) and control group (0.67±0.15) were measured. There were no statistically significant differences between two groups in ight eyes (pvalue: 0.279) and in left eyes (pvalue: 0.124).
Conclusion: The present study do not support the hypothesis of magnocellular visual pathway deficit in dyslexia. Our result show that there isn’t relationship between reading ability and contrast sensitivity in dyslexic children.

Keywords

References

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The Scientific Journal of Rehabilitation Medicine
Volume 4, Issue 2 - Serial Number 2
July and August 2015
Pages 118-126

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History

  • Receive Date: 21 October 2014
  • Revise Date: 16 January 2015
  • Accept Date: 20 February 2015
  • First Publish Date: 22 June 2015

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