Impact of co-occurring hearing and visual difficulties in childhood on educational outcomes: a longitudinal cohort study

The association between amblyopia and the risks of hearing loss: A propensity matched analysis

INTRODUCTION

Amblyopia occurs due to an imbalance in the visual input between the eyes. This can induce structural changes in the central nervous system and, if left untreated, eventually lead to permanent blindness in the affected eye. As these changes may also impact the auditory system, which closely interacts with the visual system, this study aimed to investigate the risk of hearing loss in patients with amblyopia.

MATERIALS AND METHODS

This study was a retrospective review of the electronic medical records contained in a United States national database of medical records. Patients younger than 18 years old with and without amblyopia were matched and compared to evaluate the relative risk (RR) of having a hearing loss. Stratified analyses were further performed to explore whether the disease laterality and the amblyopia subtype influenced the risks.

RESULTS

Compared to the controls, patients with amblyopia had a higher overall risk of having hearing loss (RR: 1.09, CI: 1.03-1.14), specifically sensorineural hearing loss (SNHL) (RR: 1.24, CI: 1.08-1.42). The stratified analysis further revealed that SNHL was associated with refractive amblyopia (RR: 1.84, CI: 1.50-2.26), but not strabismic amblyopia (RR: 1.23, CI: 1.10-1.38). The laterality of amblyopia did not influence the risk of hearing loss.

CONCLUSIONS

Children with amblyopia have a higher rate of SNHL than children without amblyopia. As vision and hearing are essential in the proper cognitive development, language acquisition, and social and emotional well-being of children, patients with amblyopia may benefit from more frequent audiologic screening.

Iodine status during child development and hearing ability: a systematic review

Iodine, through the thyroid hormones, is required for the development of the auditory cortex and cochlea (the sensory organ for hearing). Deafness is a well-documented feature of endemic cretinism resulting from severe iodine deficiency. However, the range of effects of suboptimal iodine intake during auditory development on the hearing ability of children is less clear. We therefore aimed to systematically review the evidence for the association between iodine exposure (i.e. intake/status/supplementation) during development (i.e. pregnancy and/or childhood) and hearing outcomes in children. We searched PubMed and Embase and identified 330 studies, of which thirteen were included in this review. Only three of the thirteen studies were of low risk of bias or of good quality, this therefore limited our ability to draw firm conclusions. Nine of the studies (69 %) were in children (one RCT, two non-RCT interventions and six cross-sectional studies) and four (31 %) were in pregnant women (one RCT, one cohort study and two case reports). The RCT of iodine supplementation in mildly iodine-deficient pregnant women found no effect on offspring hearing thresholds. However, hearing was a secondary outcome of the trial and not all women were from an iodine-deficient area. Iodine supplementation of severely iodine-deficient children (in both non-RCT interventions) resulted in improved hearing thresholds. Five of six cross-sectional studies (83 %) found that higher iodine status in children was associated with better hearing. The current evidence base for the association between iodine status and hearing outcomes is limited and further good-quality research on this topic is needed.

Amblyopia and the whole child

Amblyopia is a disorder of neurodevelopment that occurs when there is discordant binocular visual experience during the first years of life. While treatments are effective in improving visual acuity, there are significant individual differences in response to treatment that cannot be attributed solely to difference in adherence. In this considerable variability in response to treatment, we argue that treatment outcomes might be optimized by utilizing deep phenotyping of amblyopic deficits to guide alternative treatment choices. In addition, an understanding of the broader knock-on effects of amblyopia on developing visually-guided skills, self-perception, and quality of life will facilitate a whole person healthcare approach to amblyopia.

Is amblyopia associated with school readiness and cognitive performance during early schooling? Findings from the Millennium Cohort Study

Background

Amblyopia is a neurodevelopmental condition causing reduced vision, for which programmes of whole population child vision screening exist throughout the world. There is an ongoing debate about the value of screening due to the lack of evidence about meaningful functional impacts of amblyopia. Our objective was to determine whether amblyopia is associated with school readiness and early cognitive performance.

Methods and findings

Data from the prospective Millennium Cohort Study of children born in the United Kingdom in 2000–01 and followed-up to age 7 years (n = 13,967). Using parental self-report on eye conditions and treatment coded by clinical reviewers, participants were grouped into no eye conditions, strabismus alone, refractive amblyopia, or strabismic/mixed (refractive plus strabismic) amblyopia. The outcomes were poor school readiness using Bracken School Readiness Assessment <25th percentile (age 3); and cognitive tests and their age-related trajectories using British Ability Scale II Naming Vocabulary (ages 3/5) and Pattern Construction (ages 5/7). Multivariable analyses showed that compared to children without any eye conditions, only those with strabismic/mixed amblyopia had an increased risk of poor school readiness (OR = 2.04, 95%CI 1.09–3.82). Small differences in mean scores for NV and PC of children with amblyopia (all types) compared to those without any eye condition were not clinically significant (>10 points) irrespective of whether treatment had already started. The age-related cognitive trajectories of children with amblyopia did not differ from those without any eye conditions for either NV (p = 0.62) or PC (p = 0.51). These associations are at population rather than individual level, so it might be that some individuals with amblyopia did experience significant adverse outcomes that are not captured by summary statistics.

Conclusions

Amblyopia is not significantly associated with adverse cognitive performance and trajectories in early schooling and there is no evidence that this is due to a mediating effect of treatment. Although amblyopia combined with strabismus is associated with poor school readiness, this is not translated into poor cognitive performance. These novel findings may explain the lack of association reported between amblyopia and educational outcomes in adult life and suggest that the impact of amblyopia on education is not of itself a justification for whole population child vision screening aimed at detecting this disorder.