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

ABSTRACT

Purpose

Epidemiological data is essential for planning; however, all-age population-based surveys are resource intensive. Rapid Assessment of Cataract Surgical Services methodology was developed in India in 1995 and subsequently promoted by the World Health Organisation for use worldwide. The commonly used Rapid Assessment of Avoidable Blindness (RAAB) evolved from this in 2005, constraining surveys to populations aged 50 or more based on the report ‘The Epidemiology of Blindness in Nepal’ (SEVA, 1988), where 78.7% of blindness occurred in people aged 50+. The purpose of this study is to examine whether more recent total-population-based surveys continue to find a similar proportion of blindness in the population aged 50+.

Methods

A systematic literature review identified all population-based surveys of blindness published 1996–2017. Data extraction was undertaken by two independent researchers and compared.

Results

The proportions of blindness (presenting visual acuity (PVA) <3/60) and moderate/severe visual impairment (MSVI) (PVA <6/18–3/60) from total population-based surveys in people aged 50+ ranged from 90% (Mali, 1996) to 45.8% (South Korea, 2015); the mean proportions across all surveys were 73.1% (95% CI, 60.4–85.8%) for blindness, and 73.8% (95% CI, 54.8–92.8) for MSVI. No trend over time or association with GDP was identified.

Conclusion

This systematic literature review supports the rationale for constraining surveys to the population aged 50+ as this will greatly reduce sample size but still include a high proportion of total cases of blindness; paucity of total population-based surveys highlights the ongoing need for RAAB in service planning internationally.

KEYWORDS:

• blindness
• population based survey
• visual impairment
• prevalence

Summary

The factors that led to the development of RAAB (the expense and resource-intensive nature of total population-based surveys) make it perhaps unsurprising that we found just 10 total population-based surveys eligible for this review. The data showed an estimate for the proportion of all blindness that is among those aged 50 or above that is similar to that found previously, but repeating this study and reviewing the proportion of blindness in the population 50+ in another 10 years would seem prudent as demographics and eye health programs’ effectiveness continue to change. If eye health planning is based on predominantly on survey data including only those aged over 50 years of age and there should be an increase in the proportion of blindness in younger age groups, then we risk paying insufficient attention to the needs of that younger population. If there were a shift to a greater proportion of blindness occurring in the older age groups then there could be an opportunity to gain further efficiency savings in terms of time and resource by constraining surveys to an even older age group.

Disclosure statement

None of the authors have any proprietary interests or conflicts of interest related to this submission.

Financial Support

Edmund Mushumbusi was sponsored by Commonwealth Scholarship Commission (CSC), the British Council for Prevention of Blindness (BCPB), and his salary supported by the government of Tanzania. Salary for J Buchan was supported by the Queen Elizabeth Diamond Jubilee Trust through the Commonwealth Eye Health Consortium. Salary for Islay Mactaggart was supported by the Queen Elizabeth Diamond Jubilee Trust through the Commonwealth Eye Health Consortium, the UK Department for International Development, World Vision Vanuatu, Peek Vision and the Foreign Commonwealth & Development Office. Salary for D Macleod is jointly funded by the UK Medical Research Council (MRC) and the UK Department for International Development (DFID) under the MRC/DFID Concordat agreement and is also part of the EDCTP2 program supported by the European Union. Grant Reference MR/K012126/1

Additional information

Funding

This work was supported by the Commonwealth Scholarship Commission; DFID [MR/K012126/1]; Medical Research Council [MR/K012126/1]; World Vision Vanuatu; Queen Elizabeth Diamond Jubilee Trust; British Council for the Prevention of Blindness.