Welcome to the world of children's vision!

References

from:  New study: eye movement problems in dyslexic children (October 28, 2012)

A large amount of data has shown that eye movements during reading are abnormal in dyslexia and this has been reported in different languages. Pavlidis [1] was the first to show a high number of regressive saccades and unstable fixation in dyslexic population; Rayner [2] reported frequent saccades of smaller amplitude as well as longer duration fixation in dyslexic children; similarly, De Luca et al. [3] observed frequent fixations with longer duration in Italian dyslexic children and Hutzler & Wimmer [4], also showed a high number of fixations and short duration in dyslexic children. Furthermore, in Chinese dyslexic children, Li et al. [5] reported abnormal eye movements in picture searching, slow and more fixations and frequent saccades of small amplitude.A large amount of data has shown that eye movements during reading are abnormal in dyslexia and this has been reported in different languages. Pavlidis [1] was the first to show a high number of regressive saccades and unstable fixation in dyslexic population; Rayner [2] reported frequent saccades of smaller amplitude as well as longer duration fixation in dyslexic children; similarly, De Luca et al. [3] observed frequent fixations with longer duration in Italian dyslexic children and Hutzler & Wimmer [4], also showed a high number of fixations and short duration in dyslexic children. Furthermore, in Chinese dyslexic children, Li et al. [5] reported abnormal eye movements in picture searching, slow and more fixations and frequent saccades of small amplitude.

Recently, Trauzettel-Klosinski et al. [6] reported in German dyslexic children slower reading speed and high number of saccades and regressions; similar findings have been also reported in Greek dyslexic children by Hatzidaki et al. [7]. Taken together all these findings suggest that the abnormal eye movement performance observed in dyslexic children could be due to poor ability and strategy of visual information processing. Recently Jainta & Kapoula [8] reported in dyslexics poor binocular coordination of saccades during reading as well as in non reading task (while exploring a painting), while other studies on dyslexic children comparing reading and non reading tasks found ocular motor deficits in the reading task only [9],[10].

The presence of a poor visual system in dyslexics has been suggested since many years [11] who first reported dysfunction at the level of the magnocellular system in dyslexics. Following this work, many studies confirmed this hypothesis showing in dyslexic children poor binocular coordination during prolonged fixations [12], visual confusion during reading [13] and poor eye alignment during fixation after the saccade [14]. Iles et al. [15] also reported an impairment in visual search performance in a group of dyslexic adults with a motion coherence deficit confirming and extending the magnocellular hypothesis of dyslexia. Despite these results, recent research did not share the hypothesis of poor visual system, and the existence of a deficiency in the magnocellular system in dyslexia is still under debate [16],[17] [18].

Furthermore, one should also mention that apart from the visual perceptual deficiencies, visual attentional processes are involved in reading and they could be responsible for altered eye movements’ performance in dyslexic population. In this line of thinking, Bosse et al. [19] reported that some dyslexic children have a reduced visual attentional window size leading to a limitation in the number of letters which can be processed in parallel. A consequence of such a disorder is that dyslexics will make shorter saccades and frequent fixations with respect to non dyslexic children not only during reading task but also during visual search [20]. A recent fMRI study of this group [21] provided evidence on the role of parietal regions, particularly the left superior parietal area, in the visual attentional span and its deficiency in dyslexics.

1. Pavlidis GT (1981) Do eye movements hold the key to dyslexia? Neuropsychologia 19(1): 57–64.

2. Rayner K (1985) Do faulty eye movements cause dyslexia? Developmental Neuropsychology 1: 3–15.

 3. De Luca M, Di Pace E, Judica A, Spinelli D, Zoccolotti P (1999) Eye movement patterns in linguistic and non-linguistic tasks in developmental surface dyslexia. Neuropsychologia 37(12): 1407–1420.

4. Hutzler F, Wimmer H (2004) Eye movements of dyslexic children when reading in a regular orthography. Brain and Language 89(1): 235–242.

5. Li XH, Jing J, Zou XB, Huang X, Jin Y, et al. (2009) Picture perception in Chinese dyslexic children: an eye-movement study. Chin Med J (Engl) 122(3): 267–271.

6. Trauzettel-Klosinski S, Koitzsch AM, Du¨rrwa¨chter U, Sokolov AN, Reinhard J, et al. (2010) Eye movements in German-speaking children with and without dyslexia when reading aloud. Acta Ophthalmol 88(6): 681–691.

7. Hatzidaki A, Gianneli M, Petrakis E, Makaronas N, Aslanides IM (2011) Reading and visual processing in Greek dyslexic children: an eye-movement study. Dyslexia 17(1): 85–104.

8. Jainta S, Kapoula Z (2011) Dyslexic children are confronted with unstable binocular fixation while reading. PLoS One 6(4): e18694.

9. Hutzler F, Kronbichler M, Jacobs AM, Wimmer H (2006) Perhaps correlational but not causal: No effect of dyslexic readers’ magnocellular system on their eye movements during reading. Neuropsychologia 44(4): 637–648.

 10. Kirkby JA, Blythe HI, Drieghe D, Liversedge SP (2011) Reading Text Increases Binocular Disparity in Dyslexic Children. PLoS ONE 6(11): e27105.

11. Galaburda AM, Sherman GF, Rosen GD, Aboitiz F, Geschwind N (1985) Developmental dyslexia: four consecutive patients with cortical anomalies. Ann Neurol 18(2): 222–233. 

12. Stein JF, Fowler MS (1993) Unstable binocular control in dyslexic children. Journal of Research in Reading 16: 30–45.

13. Stein J, Walsh V (1997) To see but not to read; the magnocellular theory of dyslexia. Trends Neurosci 20(4): 147–152.

14. Eden GF, Stein JF, Wood HM, Wood FB (1994) Differences in eye movements and reading problems in dyslexic and non-dyslexic children. Vision Res 34(10): 1345–1358.

15. Iles J, Walsh V, Richardson A (2000) Visual search performance in dyslexia. Dyslexia 6(3): 163–77.

16. Skottun BC (2010) Rats, dyslexia, and the magnocellular system. Cortex 46(6): 799.

17. Dhar M, Been PH, Minderaa RB, Althaus M (2010) Of rats and men: A reply to Skottun. Cortex 46(6): 800–801.

18. Vidyasagar TR, Pammer K (2010) Dyslexia: a deficit in visuo-spatial attention, not in phonological processing. Trends Cogn Sci 14(2): 57–63.

19. Bosse ML, Tainturier MJ, Valdois S (2007) Developmental dyslexia: the visual attention span deficit hypothesis. Cognition 104(2): 198–230.

20. Prado C, Dubois M, Valdois S (2007) the eye movements of dyslexic children during reading and visual search: Impact of the visual attention span. Vision Res(47): 2521–2530.

21. Peyrin C, De´monet JF, N’guyen-Morel MA, Le Bas JF, Valdois S (2010). Superior parietal lobule dysfunction in a homogeneous group of dyslexic children with a visual attention span disorder. Brain Lang 118(3): 128–38.

 

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: