The importance of paediatric eye disease
Paediatric eye and vision disorders are common, but most are self-limiting or are easily fully addressed (e.g. spectacles for refractive error) or amenable to good visual outcomes after treatment: for example, amblyopia (“lazy eye”) affecting one eye occurs in between 1 and 7% of young children [
1‐
7], and good improvements in vision are achievable with treatment. In contrast, visual impairment (VI) and severe visual impairment/blindness (SVI/BL) are uncommon in the industrialised world affecting about 2 per 1000 children, usually from birth or infancy. VI and SVI/BL confers lifelong and life-changing consequences for affected individuals, their families and the societies in which they live, for example, through the significant impact on development and learning [
8‐
10].
The global burden of disease is conventionally measured using DALYs (disability-adjusted life years), but the lack of data on children, reflecting a paucity of national epidemiological studies of visual impairment [
11], means the burden of childhood blindness has to be inferred from the YLD (years lived with disability) component of DALYs, which is higher compared to adults, because it occurs so much earlier (on average 7 decades earlier) in the life course. Thus, children are a priority in VISION 2020, the WHO-led global initiative against avoidable blindness [
8,
12].
Severe visual impairment/ blindness (SVI/BL) in children is caused by a heterogeneous group of disorders which are individually uncommon. From the only national epidemiological study of incident childhood SVI/BL, which was carried out in the UK in 2000, it is estimated that in high-income countries, 4 in 10,000 children will become severely visually impaired or blind before their first birthday, with that number increasing to 6 in 10,000 before the age of 16 [
9]; from that study, the relative frequency of different underlying disorders causing SVI/BL is known. Directly comparable information for middle- and low-income settings are not available, but other studies indicate a significantly greater rate and a very different pattern of causes [
10]. Findings from an on-going national study of childhood visual impairment (VI) as well as SVI/BL, i.e.
full spectrum visual disability (acuity 0.5 LogMAR or worse in the better eye) in the UK, will provide data on incidence and the current pattern of causes [
13].
Despite the global public health importance of childhood blindness, there has not yet been a study that maps the completeness or coverage of the current evidence base on interventions to prevent or treat the major causes of childhood SVI/BL. The aim of this scoping review is to measure the distribution of robust interventional research (RCTs) across paediatric eye disease and to determine the association between the quantity of good quality RCTs and the burden of disease (relative frequency) of the key causative disorders, identifying gaps in the evidence base for tackling childhood blindness and considering the reasons for this, so as to inform research strategies and priorities.
The review will address the following questions in relation to eye and vision disease in children:
1.
How many randomised controlled trials in children have been published and how many children/young people have participated?
2.
What is the distribution of research activity (the ‘quantity’ of RCT evidence) by disease, distinguishing disorders associated with SVI/BL from those that do not cause visual impairment?
3.
What is the distribution of research activity by disease as classified by anatomical site affected and sub-classified by disorder
4.
How does the distribution of research activity by disease correlate with burden of childhood SVI/BL, as classified by comparative incidence of SVI/BL by anatomical site affected?
5.
What are the gaps in our knowledge base in terms of interventions for childhood vision and eye disease?