Magnocellular visual function in developmental dyslexia: deficit in frequency-doubling perimetry and ocular motor skills

Vilhena, Douglas de Araújo; Guimarães, Márcia Reis; Guimarães, Ricardo Queiroz; Pinheiro, Ângela Maria Vieira

doi:10.5935/0004-2749.20210069

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ORIGINAL ARTICLE • Arq. Bras. Oftalmol. 84 (5) • 2021 • https://doi.org/10.5935/0004-2749.20210069 copy

Magnocellular visual function in developmental dyslexia: deficit in frequency-doubling perimetry and ocular motor skills

Função visual magnocelular na dislexia do desenvolvimento: déficit na perimetria de frequência duplicada e nas habilidades motoras oculares

Authorship SCIMAGO INSTITUTIONS RANKINGS

ABSTRACT

Purpose:

This study aimed to verify if patients with developmental dyslexia present deficits coherent with visual magnocellular dysfunction.

Methods:

Participants with confirmed diagnosis of developmental dyslexia (n=62; age range=8-25 years; mean age=13.8 years, standard deviation=3.9; 77% male) were compared to a control group with normal development, matched for age, sex, ocular dominance, visual acuity, and text comprehension. The frequency-doubling technology perimetry was used to evaluate the peripheral visual field contrast sensitivity threshold. The Visagraph III Eye-Movement Recording System was used to evaluate ocular motor skills during text reading.

Results:

The developmental dyslexia group had significantly worse contrast sensitivity in the frequency-doubling technology, with strong effect size, than the matched control group. The developmental dyslexia group had more eyes classified in the impaired range of sensitivity threshold to detect frequency-doubling illusion than the control group. Moreover, the developmental dyslexia group had poorer ocular motor skills and reading performance, revealed by a difference in ocular fixations, regressions, span recognition, reading rate, and relative efficiency between groups. A significant correlation was found between contrast sensitivity and ocular motor skills. Participants with good relative efficiency had significantly better contrast sensitivity than participants with poor relative efficiency.

Conclusions:

The developmental dyslexia group presented a markedly worse performance in visual variables related to visual magnocellular function (i.e., frequency-doubling technology perimetry and ocular motor skills) compared with a matched control group. Professionals need to be aware of the importance of evaluating vision of individuals with developmental dyslexia beyond visual acuity and including in their assessments instruments to evaluate temporal processing, with contrast sensitivity threshold.

Keywords:
Dyslexia; Reading; Visual perception; Vision disorders; Oculomotor muscles; Eye movements

Parameters	DD group	Control group	F	p	d
Demographic and control variables
Sample size (n)	62	62		n/s	n/s
Age range (years)	8-25	8-25		n/s	n/s
Mean age (M ± SD)	13.8 ± 3.9	13.8 ± 4.4		n/s	n/s
Male (%)	77.4	77.4		n/s	n/s
Left ocular dominance (%)	37.1	37.1		n/s	n/s
Monocular visual acuity (logMAR)	0.02 ± 0.12	0.03 ± 0.12		n/s	n/s
Binocular visual acuity (logMAR)	-0.05 ± 0.11	-0.10 ± 0.10		n/s	n/s
Text comprehension (%)	78 ± 17	81 ± 16		n/s	n/s
Peripheral visual field function (FDT)
MD both eyes (dB)^* ** Significance level at 0.01; n/s=not significant; DD=developmental dyslexia.*	-3.5 ± 3.4	-0.8 ± 1.8	70.0	<0.0001	0.99
MD left eye (dB)^* ** Significance level at 0.01; n/s=not significant; DD=developmental dyslexia.*	-3.4 ± 2.9	-0.9 ± 1.5	38.6	<0.0001	1.08
MD right eye (dB)^* ** Significance level at 0.01; n/s=not significant; DD=developmental dyslexia.*	-3.7 ± 3.7	-0.7 ± 2.1	32.9	<0.0001	1.00
MD dominant Eye (dB)^* ** Significance level at 0.01; n/s=not significant; DD=developmental dyslexia.*	-3.3 ± 3.0	-0.7 ± 1.8	36.1	<0.0001	1.50
MD nondominant Eye (dB)^* ** Significance level at 0.01; n/s=not significant; DD=developmental dyslexia.*	-3.8 ± 3.7	-0.8 ± 1.9	33.9	<0.0001	1.15
MD better eye (dB)^* ** Significance level at 0.01; n/s=not significant; DD=developmental dyslexia.*	-2.6 ± 2.8	0.1 ± 1.8	44.7	<0.0001	1.15
MD worse eye (dB)^* ** Significance level at 0.01; n/s=not significant; DD=developmental dyslexia.*	-4.5 ± 3.6	-1.6 ± 1.4	35.3	<0.0001	1.06
Eyes worse than MD -2.0 dB (%)^* ** Significance level at 0.01; n/s=not significant; DD=developmental dyslexia.*	65	26	-	<0.0001	f0.48
PSD both eyes (dB)^* ** Significance level at 0.01; n/s=not significant; DD=developmental dyslexia.*	6.2 ± 2.8	5.2 ± 2.6	9.0	=0.0030	0.37
Ocular motor skills and reading parameters (Visagraph-III)
Fixations^* ** Significance level at 0.01; n/s=not significant; DD=developmental dyslexia.*	196 ± 130	155 ± 84	8.5	=0.0038	0.37
Regressions^ * Significance level at 0.05;*	61 ± 63	45 ± 34	5.8	=0.0164	0.32
Span of recognition (%)^* ** Significance level at 0.01; n/s=not significant; DD=developmental dyslexia.*	65 ± 31	87 ± 63	11.6	=0.0008	0.44
Reading rate (words per minute)^* ** Significance level at 0.01; n/s=not significant; DD=developmental dyslexia.*	158 ± 92	212 ± 124	9.7	=0.0023	0.49
Relative efficiency^* ** Significance level at 0.01; n/s=not significant; DD=developmental dyslexia.*	1.1 ± 1.2	2.2 ± 4.9	13.8	=0.0003	0.31

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[1] Corresponding author: Douglas de Araújo Vilhena. E-mail: douglasvilhena@ufmg.br