Methodological quality of the review: High confidence
Author: Powell C, Hatt SR.
Region: Not specified
Sector: Vision screening
Sub-sector: Childhood, amblyopia, screening, vision
Equity focus: Children
Review type: Effectiveness review
Quantitative synthesis method: Narrative analysis
Qualitative synthesis methods: Not applicable
Amblyopia is relatively the most common cause of reduced vision in childhood, affecting 2% of children. Normal vision is likely to be restored if amblyopia is treated, particularly while the visual system is still maturing. Screening programmes have therefore been set up to test children’s vision in order to detect the condition while the child is young and possibility of treatment. However, the effect of screening programmes to reduce the prevalence of untreated amblyopia is rare.
To evaluate the impact of vision screening on the prevalence of amblyopia in comparable screened versus unscreened populations and also determine the effect of the type of personnel conducting the testing, the age at screening, and the visual acuity threshold at which participants are referred for further evaluation.
The authors retrieved 197 references from The Cochrane Library, 655 references from Medline and 979 references from Embase. After an independent review of the titles and abstracts by two review authors, three papers were retrieved in full. However, none of the three studies met the inclusion criteria, hence excluded.
The authors found no data available from randomized controlled trials (RCTs) reporting prevalence rates of amblyopia in screened versus unscreened populations. Therefore, they discussed the current practices of a small selection of papers that were identified by electronic searches. The authors noted that the lack of data from RCTs cannot be taken to mean that vision screening was not beneficial; simply that this intervention had not yet been tested in robust trials. To facilitate such trials, the authors stated that normative data on age-appropriate vision tests needed to be available and a consensus reached regarding the definition of amblyopia. In addition, the consequences of living with untreated amblyopia had yet to be quantified and a cost-benefit carried out.
Studies that the authors set as eligible were randomized controlled trials (RCTs), including cluster-RCTs in which participants were screened before they started school; intervention was screening by formal visual acuity (VA) testing; screening carried out by monocular VA assessment using any age-appropriate vision test; screening was carried out by monocular VA assessment using age-appropriate vision test. The primary outcome measure for this review was the prevalence of amblyopia in comparable screened versus unscreened population 12 months from screening.
The authors conducted a search on different bibliographic databases including Cochrane Central Register of Controlled Trials (CENTRAL) (which contains the Cochrane Eyes and Vision Group Trials Register) (The Cochrane Library, Issue 3, 2008), Medline (January 1950 to August 2008) and Embase (January 1947 to August 2008).There were no language or date restrictions in the search for trials. The electronic databases were last searched on 15 August 2008. No manual searching was done. However, authors of studies were contacted for additional information.
All stages of study selection, data extraction were conducted by two reviewers independently. Since no trials were included in the review, none were assessed for methodological quality. No analysis was performed as the study found no trials. A small selection of papers identified by the electronic searches and some from their citation lists which describe current practice were used for discussion.
The authors reported methods that they will use in terms of assessment of methodological quality of studies, data collection, data synthesis and sensitivity analysis in future updates to this review.
The authors did not discuss the applicability/external validity of the results.
Overall, there is high confidence in the conclusions about the effects of this study. The authors conducted a thorough search of the literature to ensure that all relevant studies were identified, avoiding language bias. Appropriate methods were used in terms of study selection avoiding risk of bias. As no studies were eligible for inclusion in the review, data extraction and assessment of methodological quality was not possible. Nevertheless, the authors report methods that they will be using in future updates if studies are eligible for inclusion.