Visual and Oculomotor Function in Developmental Dyslexia: A Systematic Review and Meta-Analysis.

Area of Science:

• Ophthalmology and Vision Science
• Developmental Psychology
• Neuroscience

Background:

• Developmental dyslexia, affecting 3-6% of children, is marked by reading difficulties despite normal intelligence.
• While phonological deficits are recognized, the role of visual and oculomotor functions remains debated.
• Identifying visual anomalies could enhance assessments and interventions for dyslexia.

Purpose of the Study:

• To investigate visual and oculomotor function differences in individuals with developmental dyslexia compared to controls.
• To synthesize evidence from observational studies through a systematic review and meta-analysis.

Main Methods:

• Systematic review and meta-analysis of observational case-control studies (PROSPERO registration).
• Searches across PubMed, Web of Science, and Scopus for studies on visual/oculomotor functions in dyslexia.
• Included outcomes: binocular vision, oculomotor performance, accommodation, visual acuity, refractive error, contrast sensitivity.

Main Results:

• Twenty-six studies included; dyslexic individuals showed greater near exophoria and reduced fusional vergence ranges.
• Oculomotor differences included more fixations, longer fixation duration, more regressions, and reduced saccade amplitude.
• No significant differences were found in refractive error or visual acuity between groups.

Conclusions:

• Children with developmental dyslexia exhibit consistent binocular and oculomotor anomalies.
• These anomalies may increase visual effort during reading, impacting performance.
• Targeted vision assessments could complement multidisciplinary dyslexia management.