A Systematic Review on Visual-Processing Deficits in Neurofibromatosis Type 1: What Possible Impact on Learning to Read?

ABSTRACT

This systematic review aimed to examine the possible implication of visual-perceptual, visuo-attentional and oculomotor processing in the reading deficits frequently experienced by children with Neurofibromatosis type 1 (NF1), as previously shown in dyslexia. Using PRISMA methodological guidelines, we examined 49 studies; most of these reported visual-processing deficits in this population, raising the importance of directly studying the visuo-perceptual and visuo-attentional processes and eye-movement control involved in the learning-to-read process in NF1. The discussion provides a reflection for a better understanding of how visual-processing skills interact with reading deficits in NF1, as well as new avenues for their screening and care.

Acknowledgments

The authors are very grateful to the “Association Neurofibromatoses et Recklinghausen” (France) and the “Fondation de France” for their support and financial contributions to this project. We are also grateful to N. Sghaier for her valuable information and advice.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Notes

1. For a discussion on the differences between perceptual, visual and visual-attentional spans see Frey and Bosse (2018).

2. The level of perceptual processing was introduced by Navon (1977), using cross-level hierarchical stimuli to study (1) the primacy of one level over the others and (2) the factors affecting this process.

3. The visual crowding effect corresponds to the identification of a visual target being harder due to interference from surrounding visual objects, compared to when it is isolated.

4. Note that the literature search on the Embase database was conducted in March 2022 considering papers before January 2022. This search could not be updated in 2023 due to access rights to this database.

5. Note that this section includes only visuo-perceptual processes with reduced motor involvement. Perceptual-motor processes will be discussed in a subsequent section.

6. Note that lateral dominance was not taken into account in this study, although structural changes may occur in NF1.

7. In this task, the stimuli correspond to a large letter (global shape) composed of smaller letters (local shape). The congruency between the global and the local letters is manipulated. Participants are instructed to name the letter at a specific level of visual processing, either at the global or local level.

8. In this section, a distinction was made between visual-motor and saccadic processes since these terms refer to two distinct literatures. The term visual-motor is specifically used in the context of grapho-motor tasks involving eye-hand coordination such as figure copying and line tracing between contours tasks.

9. Note that the results provided by Gilboa et al. (2010) and Gilboa et al. (2014) used the same cohort and the same results in the two studies but comparing NF1 children with control subjects in one study and with normative data in the other. The same approach was performed in Krab et al. (2008) and Krab et al. (2011).

10. The term saccadic system here does not include what is related to eye-movement control in reading since no studies to our knowledge were conducted in this field.

11. Note that the 81 NF1 children of the study by Hyman et al. (2005) were also included in the 199 NF1 children of the study by Payne et al. (2011). Thus the divergent results of these two studies could be attributed to differences in the sample sizes: it is possible that the significant effect found in the Payne et al. (2011) study may be more representative of the NF1 population due to the large sample size of this study.

12. We thank Reviewer 1 for this suggestion.

Additional information

Funding

This work was funded by a PhD Fellowship from the “Fondation de France” and the “Association Neurofibromatoses et Recklinghausen” provided to the first author [VISALECT_NF1_00099576].