Global estimates on the number of people blind or visually impaired by cataract: a meta-analysis from 2000 to 2020

Author: Vision Loss Expert Group of the Global Burden of Disease Study

Geographical coverage: Southeast Asia, East Asia, Oceania, Central Europe, Eastern Europe, Central Asia, High-income, Latin America and the Caribbean, North Africa and the Middle East, South Asia, Sub-Saharan Africa

Sector: Burden of Disease

Sub-sector: Prevalence, blindness and visual impairment due to cataracts

Equity focus: Not reported

Study population: Population with cataracts

Review type: Effectiveness review

Quantitative synthesis method: Meta-regression

Qualitative synthesis method: Not applicable

Background

In 2020, the GBD Study reported cataract as the leading cause of blindness, with 15.2 million cases and 78.8 million affected by MSVI. Despite progress, inequalities remain, particularly in low- and middle-income countries. The study aims to update global estimates using the Global Vision Database.

Objective

To estimate global and regional trends from 2000 to 2020 in the number of people visually impaired by cataract and the proportion this represents.

Main findings

The study found 17.01 million people were blind due to cataracts in 2020, and 83.48 million had MSVI. While age-standardised cataract-related blindness fell by 27.54%, the absolute number rose by 29.72%. MSVI cases increased by 93.11%, especially in Southeast Asia and Oceania.

Methodology

A systematic review included 137 population-based studies and data from RAAB, NHANES, and WHO SAGE. Data were processed using MR-BRT and DisMod-MR 2.1 to estimate prevalence by age, sex, location, and year.

Applicability/external validity

Findings are applicable globally with variations by region. Cataract contributed more to blindness in South Asia and Southeast Asia than in other regions.

Geographic focus

Studies were included from all major world regions.

Summary of quality assessment

Confidence in the findings is low due to limitations in literature search, unclear methods for screening and data extraction, and lack of detailed risk of bias assessment.