The Global extent of undetected glaucoma in adults

Author: Soh Z, Yu M, Betzler BK, Majithia S, Thakur S, Tham YC, Wong TY, Aung T, Friedman DS, Cheng CY.

Geographical coverage: Asia, Africa, Oceania, Europe, Latin America, Caribbean, North America

Sector: Glaucoma

Sub-sector: Epidemiology

Equity focus: Not reported

Study population: Adults with glaucoma

Review type: Epidemiology review

Quantitative synthesis method: Meta-analysis

Qualitative synthesis method: Not applicable

Background 

Despite advances in treatment, glaucoma remains the leading cause of irreversible blindness. The condition is typically asymptomatic in its early stages and progresses slowly, making prompt detection difficult. Estimates of undiagnosed disease range from 33 % to 98 %. Primary open-angle glaucoma (POAG) disproportionately affects people of African descent, whereas primary angle-closure glaucoma (PACG) is more common in Asian populations.

Objectives 

To determine the worldwide extent of undetected glaucoma and to identify factors associated with non‑detection.

Main findings

A substantial proportion of glaucoma cases remain undiagnosed worldwide, with the highest prevalence in resource‑limited regions.

The search identified 8 947 records; 55 population‑based ophthalmic studies (61 articles) involving 189 359 participants met the inclusion criteria. Twenty‑four studies (30 articles) were conducted in Asia, eight in Africa, four in Oceania, 12 in Europe, five in North America and two in Latin America and the Caribbean.

Across all regions more than half of glaucoma cases were undetected. For manifest glaucoma, the greatest proportion of previously undiagnosed cases was found in Africa (94.13 %; 95 % confidence interval [CI] 91.24 % to 96.11 %), and the lowest in Oceania (59.09 %; 95 % CI 48.63 % to 68.79 %). Compared with Europe, the odds of undetected manifest glaucoma were significantly higher in Africa (odds ratio [OR] 12.70; 95 % CI 4.91 to 32.86) and Asia (OR 3.41; 95 % CI 1.63 to 7.16); differences between Europe and other regions were not statistically significant.

For POAG, the highest proportion of undetected cases was again observed in Africa (92.35 %; 95 % CI 84.08 % to 96.50 %) and the lowest in North America (57.27 %; 95 % CI 41.56 % to 71.64 %). Relative to Europe, the odds of undetected POAG were markedly higher in Africa (OR 8.84; 95 % CI 2.64 to 29.62) and Asia (OR 4.66; 95 % CI 2.07 to 10.51).

Countries with a low Human Development Index (HDI < 0.55) showed a greater mean proportion of undetected manifest glaucoma (94.56 %; 95 % CI 92.13 % to 96.27 %) than countries with medium (78.67 %; 95 % CI 70.62 % to 84.99 %) or very high HDI (71.43 %; 95 % CI 63.10 % to 78.52 %) (all P < 0.001). In 2020, an estimated 43.78 million POAG cases were projected to remain undetected, 76.7 % of which were in Africa and Asia.

Methodology 

Systematic searches of PubMed, Web of Science, OpenGrey and non‑governmental organisation websites (Rapid Assessment of Avoidable Blindness repository, Global Burden of Disease surveys, Global Health Data Exchange repository, World Health Organization database and International Agency for the Prevention of Blindness database) were carried out to identify population‑based studies published between 1 January 1990 and 1 June 2020. Studies were included if they achieved a response rate of at least 60 %, clearly defined the sampling frame and procedure, and performed visual‑field (VF) testing to confirm functional loss attributable to glaucoma.

Two reviewers independently screened titles and abstracts, assessed full‑text eligibility and evaluated risk of bias using the Joanna Briggs Institute Critical Appraisal Checklist for Prevalence Studies. Disagreements were resolved through consultation with a third reviewer. Reference lists of relevant reviews were scanned to identify additional publications.

Data were extracted into a standardised form and synthesised using a random‑effects meta‑analysis. Heterogeneity was assessed with the I² statistic and the χ² test. Multivariable meta‑regression examined variation by geographical region, ethnicity, HDI, setting, response rate and study year. Subgroup analyses were pre‑specified, and publication bias was evaluated with a funnel plot and the Begg–Mazumdar test.

Applicability / external validity

The review provides the most comprehensive estimate to date of undetected glaucoma worldwide, but external validity is limited by sparse data from certain high‑risk areas (for example, South Asia) and heterogeneity in study methods.

Geographic focus

The included studies were conducted in Asia, Africa, Oceania, Europe, Latin America, the Caribbean, and North America.

Summary of quality assessment

Eleven potentially relevant publications were excluded without explanation, the number of reviewers involved in data extraction was not reported, no list of excluded studies was provided and there was no evidence that study authors or experts were contacted for clarifications.