Binocular vision anomalies in children with dyslexia in Kano, Nigeria

Abstract

Dyslexia is a specific neurological learning disorder characterized by persistent difficulties in acquiring reading skills, leading to poor academic performance. While vision plays a direct role in the reading process, little is known about the integrity of visual function in individuals with dyslexia. The treatment of vision-related problems in dyslexia may require a multidisciplinary approach. Currently, there is a lack of data and studies focusing on the optometric evaluation of binocular vision in children with learning disorders in Kano, Nigeria. This study aims to investigate binocular vision anomalies (BVA) in dyslexic children and compare them with a control group, which will help inform the development of treatment services. This cross-sectional study was carried out at Aminu Kano Teaching Hospital. Kano, Nigeria. A total of 44 children, aged and gender-matched (mean age: 11.9 ±1.72 years old) were recruited. 22 children were dyslexic (cases) and 22 non-dyslexic children (controls) participated in this study. A series of visual function and binocular vision tests were performed on both groups. The anomalies were more prevalent in males and children under the age of 12. The dyslexic children were significantly more from a low socio-economic status than the non-dyslexic group (31.8% vs 9.1%, p=0.07). The significant clinical ocular signs and symptoms presented were eyestrain (75% vs 18.8%, p= 0.001), visual distortions (68.2% vs 33.3%, p= 0.02), and blurring vision (95.5% vs 50%, p= 0.001), while the significant non-ocular signs and symptoms noted were general vocabulary skills (13.3% vs 53.3% p= 0.02). The study findings indicate that both groups exhibited BVA, though slightly higher in the dyslexic group with a prevalence rate of 100% and 90.9% respectively. The result from the mean differences between groups show that only the recovery value of DPFV was found to be significantly different with a median IQR range of 4.0 (2.0 – 6.5) ΔD and 8.0 (4.0 – 10.0) ΔD for dyslexic and non-dyslexic group respectively (p= 0.005), also the horizontal DEM was higher and statistically different between group (p= 0.04). The most common BVA is accommodative insufficiency, either alone or in combination with convergence insufficiency, with higher rates observed in the dyslexic group (45.5%). Convergence insufficiency was more prevalent in the non-dyslexic group (22.7%). These findings highlight the association between BVA and dyslexia, underscoring the importance of vision assessments for all children. In conclusion, this study demonstrates a slightly higher prevalence of BVA and ocular signs and symptoms in the dyslexic group. Further research is needed to correlate symptoms, visual problems, and reading abilities, as well as to explore potential interventions to improve and alleviate symptoms. It is worth noting that the uneven gender distribution in the recruitment process may introduce bias into the findings. This research will contribute to the initial steps in formulating appropriate strategies for dyslexia treatment. Additionally, the study results will facilitate the development of a suitable binocular vision testing paradigm for dyslexia and provide insights for future research within the Nigerian population.