A systematic review of the proportion of blindness in the population 50 years and older from total population-based surveys of blindness and visual impairment

Author: Mushumbusi E, Buchan J, Mactaggart I, Macleod D, Foster A.

Geographical coverage: Asia, Africa and South Korea

Sector: Burden of disease

Sub-sector: Prevalence

Equity focus: Not reported

Study population: Patients with blindness or visual impairment

Review type: Effectiveness review

Quantitative synthesis method: Meta-analysis

Qualitative synthesis method: Not applicable

Background:

Under the WHO’s VISION 2020: The Right to Sight initiative, countries are urged to gather reliable data to inform national eye-care programmes. Full population surveys are expensive, so rapid methodologies—initially RACSS and later the Rapid Assessment of Avoidable Blindness (RAAB)—were developed to focus on those aged ≥ 50 years, the age group thought to harbour most blindness. Two decades on, demographic change and shifting disease patterns may have altered that proportion.

Objective:

To assess whether recent total-population surveys still show a similar share of blindness in the ≥ 50 age group to that reported by the SEVA Foundation in Nepal (78.7 %).

Main findings:

Ten eligible surveys were identified. The proportion of all blindness occurring in people aged ≥ 50 years ranged from 45.8 % (South Korea, 2015) to 90.2 % (Mali, 1996); the pooled mean was 73.1 % (95 % CI 60.4 – 85.8 %). For moderate/severe visual impairment (MSVI) in the 50+ age group ranged from 50.3% in South Sudan (2006) to 89.5% in China (2012), with a mean of 73.8% (95% CI: 54.8% to 92.8%). %). No temporal trend was evident. National GDP per capita did not correlate with the proportion of blindness in the ≥ 50 group, although overall blindness prevalence was lower in wealthier nations (p = 0.014). Causes mirrored global patterns: cataract predominated, but onchocerciasis, refractive error, retinal disease and trachoma were locally important.

Overall, the results support the continued use of RAAB surveys focused on the 50+ age group for efficient and effective eye health planning, though the variability in findings underscores the need for occasional reassessment and caution in extrapolating results to entire populations.

Methodology:

PubMed, EMBASE, Global Health, Web of Science and the Cochrane Library were searched for English-language, population-based blindness surveys published January 1996 – July 2017. Inclusion required WHO ICD-10 definitions and sampling frames covering the entire population or ≥ 6-year-olds. Two reviewers independently screened, extracted data and resolved disagreements by discussion. Study quality was appraised with the Cochrane Risk of Bias tool and findings were synthesised narratively.

Applicability / external validity:

Total population surveys remain scarce, limiting firm validation of RAAB estimates. Wide inter-survey variation cautions against blanket extrapolation from ≥ 50 data to whole populations. Nonetheless, the consistently high share of blindness in this age group supports continued RAAB use for efficient planning, provided results are interpreted in context.

Geographic focus:

Surveys were conducted in Asia and Africa (all low- and middle-income countries) and one high-income setting (South Korea). No geographical limits were applied.

Summary of quality assessment:

Searches were comprehensive and criteria explicit; dual-reviewer screening and data extraction were employed, and established quality tools used. Limitations include the English-language restriction, absence of an excluded-studies list and no reported reference-list checking. Overall confidence in the conclusions is low.