Near Phoria and Near Point of Convergence Parameters in Children With Hearing and Speech Impairment: A Cross-Sectional Study

Abstract

Background and aims: Children with hearing and speech impairment are reported to have a higher prevalence of refractive errors and amblyopia. Most studies conducted previously have not primarily concentrated on the binocular vision aspects of near vision in children with hearing impairment (HI). The aim of this study was to investigate and compare the parameters of near phoria and near point of convergence (NPC) among hearing and speech impaired school children with age matched control group of emmetropic non hearing-impaired Children.

Methods: A total of 279 participants in the age range of 6-15 years participated in this study. Children with ametropia, distance visual acuity lower than 20/30 (0.2 Log MAR), N6 at 40 cm and ocular abnormalities other than non-strabismic binocular vision abnormalities, were excluded from the study. Children who passed the vision screening, and who had no other ocular abnormalities underwent testing for near phoria and near point of convergence.

Results: Statistical analyses between the two groups showed that children with HI had a higher median (± IQR) value of near phoria (-3 ± 5 Δ) and receded NPC (10 ± 5 cm) compared to age matched controls (near phoria: -1 ± 3 Δ, NPC: 6 ± 5 cm). This difference was statistically and clinically significant (Mann Whitney U test, Near Phoria p < 0.005, NPC p < 0.05). The prevalence of Convergence Insufficiency (CI) was 33.33% in the hearing and speech impaired group when compared to 20.43% among age matched controls (Z-test, p < 0.05).

Conclusion: A higher percentage of children with hearing and speech impairment have receded near point of convergence and larger exophoria compared to their age matched non hearing-impaired counterparts. Since children with hearing impairment depend primarily on visual means of communication by sign language and through understanding signs and facial expressions, it is especially important to diagnose and offer treatment to all visual conditions causing possible detriment to vision.

Keywords: binocular vision; convergence insufficiency; deafness; exophoria; hearing impairment; near phoria; near point of convergence; non‐strabismic binocular vision anomalies; speech impairment.