Global and regional prevalence of age-related cataract: a comprehensive systematic review and meta-analysis

Author: Hashemi H, Pakzad R, Yekta A, Aghamirsalim M, Pakbin M, Ramin S, Khabazkhoob M. 

Geographical coverage: the Western Pacific, South-East Asia, Europe, the Americas, the Eastern Mediterranean and Nigeria

Sector: Burden of disease

Sub-sector: Epidemiology, age-related cataracts

Equity focus:  Not reported

Study population: Patients with cataract

Review type: Effectiveness review

Quantitative synthesis method: Meta-analysis

Qualitative synthesis method: Not applicable

Background:

Cataract remains a leading cause of visual impairment worldwide and continues to pose a major public-health challenge in both high- and low-income countries. More than 90 % of cataract-related disability-adjusted life-years are borne by populations in developing nations. Although ageing is the principal risk factor, ultraviolet exposure, diabetes and smoking also contribute to lens opacification. Over the past three decades numerous population-based investigations have mapped prevalence patterns across ethnic and regional groups, information that is essential for planning effective public-health interventions and services.

Objective:

To estimate global and regional cataract prevalence, assess age-specific rates, and explore sources of heterogeneity.

Main findings:

Forty-five studies (161 947 participants) published between 1994 and 2019 were included in the review. Minimum and maximum study ages ranged from 19–29 years and 90–99 years, respectively. Six WHO regions were represented, but only one study originated from Africa (Nigeria). Study quality was rated very good (23), good (14) or satisfactory (3).

• Age-standardised pooled prevalence estimates (ASPPE):
  • Any cataract – 17.20 % (95 % CI 13.39 – 21.01)
  • Cortical cataract – 8.05 % (95 % CI 4.79 – 11.31)
  • Nuclear cataract – 8.22 % (95 % CI 4.93 – 11.52)
  • Posterior subcapsular (PSC) cataract – 2.24 % (95 % CI 1.41 – 3.07)
• Age-group prevalence of any cataract:
  • 20–39 years – 3.01 % (95 % CI 1.68 – 4.34)
  • 40–59 years – 16.97 % (95 % CI 11.36 – 22.57)
  • ≥ 60 years – 54.38 % (95 % CI 47.57 – 61.18)
• Prevalence varied by WHO region and increased steeply with age.

Methodology:

PubMed, Embase, Web of Science, Scopus, and Google Scholar were searched up to 13 August 2019 for cross-sectional or cohort studies that applied Lens Opacity Classification System (LOCS) II or III grading in general populations. Two reviewers independently screened records, extracted data, and appraised quality with the Newcastle–Ottawa Scale. Pooled estimates were calculated using fixed- or random-effects meta-analysis; heterogeneity was examined with the Cochran Q-test and I², while meta-regression explored potential modifiers. Publication bias was assessed via funnel plots, with trim-and-fill adjustment when necessary.

Applicability / external validity:

Generalisability is restricted by under-representation of several regions—particularly Africa—and by exclusion of studies that used non-LOCS grading systems. Variation in diagnostic methods and demographics across studies further limits applicability to settings that differ markedly from those reported.

Geographic focus:

Studies were conducted in the Western Pacific (19), South-East Asia, Europe, the Americas, the Eastern Mediterranean and Africa (one Nigerian study). No geographical restrictions were imposed.

Summary of quality assessment:

Searches were comprehensive and eligibility criteria were explicit; dual-reviewer screening and quality appraisal followed established standards. Study characteristics were fully reported, and appropriate statistical methods were used to address heterogeneity and potential publication bias. Limitations include absence of an excluded-studies list, unreported independence of data extraction, and sparse data from some regions, which collectively yield low overall confidence in effect estimates.