Methodological quality of the review: High confidence

Author: Sheeladevi S, Lawrenson JG, Fielder AR and Suttle CM

Region: Global

Sector: Prevalence of cataract

Type of cataract: Paediatric cataract

Equity focus: None specified

Quantitative synthesis method: Narrative synthesis

Qualitative synthesis method: Not applicable

Background:

Childhood cataract is an avoidable cause of visual disability worldwide and is a priority for VISION 2020: The Right to Sight. There is a paucity of information about the burden of cataract in children.

Research objectives:

The aim of this review is to assess the global prevalence of childhood cataract.

Main findings:

Twenty prevalence and four incidence studies of childhood cataract from five different geographical regions including Europe and Central Asia (n= 8), South Asia (n=3), East Asia and Pacific (n=8), Sub-Saharan Africa (n= 3), and North America (n=2) were included in the review. Authors note that studies were generally of moderate to good methodological quality, although they were often poorly reported. In addition, authors identified a considerable degree of heterogeneity between the 20 studies reporting prevalence of childhood cataract (Cochran’s Q-test, Po0.01; I2 =94%).

The overall prevalence of childhood cataract and congenital cataract was in the range from 0.32 to 22.9/10,000 children (median=1.03) and 0.63 to 9.74/10,000 (median=1.71), respectively. The incidence ranged from 1.8 to 3.6/10,000 per year. The prevalence of childhood cataract in low-income economies was found to be 0.42 to 2.05 compared with 0.63 to 13.6/10,000 in high-income economies.

There was no difference in the prevalence based on laterality or gender. This review highlights substantial gaps in the epidemiological knowledge of childhood cataract worldwide, particularly from low and lower middle-income economies. More studies are needed using standard definitions and case ascertainment methods with large enough sample sizes.

Methodology:

Authors included all studies at any global location which estimated the prevalence and/or incidence of cataract among children (aged less than 18 years). In this context, prevalence indicates the number of children in a population that have cataract at a given point of time divided by those at risk (the total number of children in the population sample).

Authors conducted a search on following databases The Cochrane Library, Medline, and Embase. No language or date restrictions were applied. Bibliographies of related articles were checked to identify additional potentially relevant reports. The WHO website was searched for program reports and government documentation.

Two authors independently screened studies for inclusion, extract data and quality assessment of included studies. Authors used the prevalence critical appraisal instrument developed by Munn et al. Heterogeneity was assessed using Cochran’s Q chi-squared statistic and by calculating the I2. Prevalence was assessed for geographical location according to income status, defined according to the gross national income per capita per year and calculated using the World Bank Atlas method. Correlation tests were used to correlate variables with Po0.05 considered as statistically significant.

Applicability/external validity:

Authors report the median prevalence of childhood cataract as 1.03 per 10,000 (range 0.32-22.9/10,000) children. Over 90% of cataracts were classified as congenital or developmental. However, authors note that it is not clear whether the wide range in reported prevalence values reflects true variances between populations or whether this is due to differences in methodology and/or case definitions used in the included studies.

Geographic focus:

Authors note that the prevalence of childhood cataract in low-income economies was found to be 0.42 to 2.05, and that there are substantial gaps in the epidemiological knowledge of childhood cataract worldwide, particularly from low and lower middle-income economies.

Quality assessment:

Overall, there is high confidence in the conclusions about the effects of this review. Authors used rigorous methods to ensure that publication bias was avoided. In addition, used appropriate methods to screen studies for inclusion, assess methodological quality and extract data of included studies.