We searched Medline, Embase, PsychINFO, and the Cochrane library for papers published between January, 1995, and December, 2013 (appendix pp 1–2). We used the search terms “randomised control trial”, “cohort”, “case-control or longitudinal’, “child or preschool”, “amblyopia”, “strabismus”, “squint”, “hypermetropia or myopia or anisometropia”, “screening”, and “prevalence or surveillance”. Systematic reviews, randomised, controlled trials, and population-based observational studies were
ReviewWhole-population vision screening in children aged 4–5 years to detect amblyopia
Introduction
Developmental neuroplasticity starting at birth drives structural and functional changes in the eye and brain during maturation of the visual system. Amblyopia is a neurodevelopmental disorder that arises secondary to disruption of normal processes during this sensitive period. It most commonly arises because of visual blur from defocus (refractive amblyopia), failure to maintain alignment of the eyes (strabismic amblyopia), structural disorders of the eye, such as cataract, that obscure incoming images (form-deprivation amblyopia), or a combination of these features. Both eyes might be affected, but the disorder is predominantly unilateral, and is generally associated with impaired or absent stereoacuity (depth perception).1, 2 Any childhood ocular disorder carries a risk of amblyopia and, therefore, it is the most prevalent disorder managed in paediatric ophthalmology. Standard clinical practice is to implement treatment within the critical period, which is thought to span from infancy to around age 7–9 years, to improve vision and enable development along as normal a vision trajectory as possible.3
Visual acuity is the key visual function. WHO and other organisations use acuity in the better eye to classify individuals as non-impaired, visually impaired, severely visually impaired, or blind.4 Thus, individuals with reduced acuity in one eye, irrespective of severity, are not classified as visually impaired. In the UK, in more than 97% of children with severely reduced vision in both eyes the diagnosis is made early in childhood.5 Diagnosis frequently arises owing to the concerns of carers and caregivers or in the context of the routine universal Newborn and Infant Physical Examination programme (figure 1) or other disorder-specific screening programmes. As amblyopia is a developmental disorder, affected children may grow up without a comparative visual experience and are likely to be unaware of the poorer vision in the amblyopic eye. Thus, screening at age 4–5 years is primarily aimed at identifying unilateral impaired vision with the aim of beginning intervention early.
In 1995, Snowdon and Stewart-Brown6 reported a systematic review of childhood vision screening to detect amblyopia that was commissioned by the UK Health Technology Assessment body, which is responsible for independent assessment of effectiveness, costs, and effects of health-care interventions. They showed an absence of good quality research into efficacy of treatments for and disability associated with amblyopia. The conclusion was a recommendation that the UK National Screening Committee, the body responsible for the continuation, modification, or withdrawal of existing population screening programmes, consider whether to discontinue screening.6 The findings were opposed by the international ophthalmic community, but did lead to a rationalisation of the existing practices in the UK. The findings also led to substantial primary research throughout the world that began to provide information on whole-population childhood vision screening programmes, which exist in most industrialised countries.
We undertook a systematic review of the evidence on childhood vision screening to detect amblyopia (figure 2, appendix pp 1–3). Here we summarise our findings, focusing on the fundamental public health issues—the appropriateness and effectiveness of universal childhood vision screening and the effectiveness of treatments for amblyopia.7 For brevity we do not report on factors such as screening for risk factors or other conditions that might predispose to amblyopia or on screening thresholds. Similarly, we do not discuss other screening programmes, such as neonatal and infant programmes to detect major eye anomalies or screening of preterm children for retinopathy of prematurity, or best practice clinical surveillance of children at increased risk of ophthalmic disorders, such as those with hearing impairment or neurodevelopmental disorders.
Section snippets
Definitions and prevalence of amblyopia
Vision matures owing to structural and functional development of the eyes and visual pathways in early childhood. By definition, vision of 0·0 logMAR (6/6 Snellen) is taken to be normal adult acuity. Neonates have an average acuity worse than 1·0 logMAR (6/60), which improves to near adult levels by age 5–6 years.8 As there is no internationally agreed definition or vision threshold for amblyopia, reported prevalence varies (Table 1, Table 2). This variation is compounded by substantial
Effects of amblyopia
Impaired vision in both eyes is recognised as having substantial effects on development, health, and quality of life, but the Health Technology Assessment body report by Snowdon and Stewart-Brown6 found no robust evidence of disability in individuals with unilateral amblyopia. Research has since been directed at understanding the effects of reduced vision in one eye. Inconsistent associations have been made between unilaterally reduced vision in adulthood and impairment of mental health,
Effectiveness
The natural history of untreated amblyopia in human beings is not well documented, which is unsurprising as screening and treatment have long been established. The existing data, however, support the notion of a sensitive period for diagnosis and treatment.
Conventional treatment comprises correction of the amblyogenic defect, most commonly by refractive correction combined with so-called penalisation of the non-amblyopic eye through physical (occlusion with patches) or pharmacological
Effectiveness
A European population-based cohort study showed a low rate of residual amblyopia (0·8%) at age 7 years in children who underwent intensive screening (seven assessments by age 6 years) compared with published rates for unscreened populations.82 This finding supports a positive effect with screening. No randomised controlled trials, however, have shown that vision screening in children aged 4–5 years efficaciously lessens morbidity and other health effects. Thus, several systematic reviews have
Conclusions
We have found no robust evidence to support making significant changes to the overall content of the existing UK National Screening Committee's recommended programme for children aged 4–5 years, despite being more conservative than the intensive programmes of repeated testing up to age 5 years in other European countries. This finding is noteworthy in view of the European Union Horizon 2020 initiative on screening.100 Also of note is that revisions to the US national recommendations99 bring the
Search strategy and selection criteria
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Cited by (73)
Utilization and barriers to eye care following school-wide pediatric vision screening
2023, Canadian Journal of OphthalmologyThe cost-effectiveness of different visual acuity screening strategies in three European countries: A microsimulation study
2022, Preventive Medicine ReportsCitation Excerpt :The calibration of the model is performed on the Dutch OVAS study that may be less representative for other countries, because of the high acceptability of screening, high coverage of screening and treatment, awareness and good public health infrastructure in the Netherlands. Although the prevalence of amblyopia seems about the same in different countries (Solebo et al., 2015), it is possible that the type or severity of amblyopia differs. In addition, we only modeled VA measurement and not photorefraction, since the impact of photorefraction on the reduction in the development of amblyopia is unknown and the test is rarely used as stand-alone test in Europe (Rostamzad et al., 2020; Horwood et al., 2021).
Visual acuity percentile curves in a Spanish paediatric population
2022, Journal of OptometryImpact of Persisting Amblyopia on Socioeconomic, Health, and Well-Being Outcomes in Adult Life: Findings From the UK Biobank
2021, Value in HealthCitation Excerpt :Nevertheless, population-based estimates for this are lacking, which limits the ability to counsel patients at the start of treatment. Universal childhood vision screening programs targeting amblyopia exist worldwide.1,2,9-11 One justification is the prevention of vision impairment later in life in the uncommon event of disease or injury affecting the nonamblyopic eye, rendering reliance on the amblyopic eye.12-14