A cross-sectional investigation of binocular function, screen time and visual fatigue in children with dyslexia

Dyslexia is a specific learning disorder characterized by difficulties in reading, spelling, and writing. Previous studies suggested that individuals with dyslexia may experience binocular function abnormalities and visual fatigue. However, most studies investigating these issues have been conducted elsewhere outside Malaysia, leaving a population gap with local data. Therefore, this study aimed to address this gap by examining the visual and binocular vision status of children with dyslexia. Visual fatigue symptoms and screen time exposure were also investigated and compared with typically developing peers as these two are related to binocular function. Method: This cross-sectional study involved 137 students with dyslexia aged 13 to 19 (M=15.24; SD= 1.75) years from 15 secondary schools with Program Pendidikan Khas Integrasi (PPKI) across three districts in Selangor. Refractive and binocular assessments were conducted at the respective schools, while screen time exposure and visual fatigue symptoms were evaluated using a validated questionnaire. As a comparison, screen time exposure and visual fatigue symptoms were also gathered from 83 typically developing students with mean age of 14.59±1.42 years. Results: 88% of the dyslexic children had a good visual acuity (VA) of 6/9 or better at distance while 95% of them had a good VA of N6 or better at near. Refractive errors were found in 49% of the dyslexic group with myopia (44%) and astigmatism (59%) being the most common type of refractive error, followed by hyperopia (5%). The most commonly impaired accommodation parameters were lag of accommodation (67%), binocular and monocular facility of accommodation (50-59%), and negative relative of accommodation (55%). Despite the majority of them being orthophoric, exophoria was the most common type of ocular deviation at near (29%) and distance (19%). Based on the binocular function findings, the most common type of binocular vision anomalies were convergence insufficiency, accommodation insufficiency and accommodation infacility. Screen time exposure and visual fatigue score were significantly higher in typically developing students compared with the dyslexic group. Pearson’s correlation revealed a significant correlation between screen time exposure and visual fatigue symptoms during weekdays (p= 0.02, r=0.25) and weekends (p=0.002, r=0.33) only in typically developing but not dyslexic group. Multilinear regression showed near point of convergence was a significant predictor for visual fatigue symptoms score in dyslexic children.