Photo credit: Heiko Philippin

Glaucoma is the leading cause of irreversible blindness globally. In 2020, 3.6 million people over 50 years of age were blind globally due to the condition, and there are estimated to be 112 million people with glaucoma by 2040. Early detection and treatment are crucial to slow or prevent vision loss, but there are major disparities between countries and populations that mean some are more likely to lose sight than others.

There is existing evidence that race, gender, location and socioeconomic status can lead to unequal outcomes for glaucoma, and globally there is a higher prevalence of glaucoma and glaucoma-blindness in sub-Saharan Africa compared to elsewhere. Inadequate diagnosis and management of glaucoma in low-income countries is compounded by limited health infrastructure and technology, decreased access to medical and surgical treatment, and in turn, more advanced disease at presentation.

Research into glaucoma can help to reduce these inequities, but only when it considers disadvantaged groups. Systematic reviews, where the results of many studies are analysed and conclusions drawn from their findings, are often used to inform guidelines (for instance the American Academy of Ophthalmology POAG guidelines were designed in partnership with the Cochrane Eyes and Vision US Project which incorporates Cochrane systematic reviews), but are reliant on the type of data they assess. When research fails to consider equity, it may perpetuate or further increase inequities experienced by some groups.

A new study including researchers from the International Centre for Eye Health aimed to evaluate the extent of equity considerations for glaucoma in Cochrane Reviews (a database of systematic reviews and meta-analyses) and a sample of primary studies within them.

The authors analysed 40 systematic reviews in the Cochrane Library (which comprised all reviews from its inception in 2003 to 31st January, 2024) and a sample of 122 recently published primary studies.

The systematic reviews exclusively included randomised controlled trials (RCTs) or quasi-RCTs. Twenty-nine (72.5%) reviews acknowledged populations experiencing inequities in glaucoma care, but none were able to analyse these subgroups due to the data being unavailable in the primary studies included in the review.

Forty seven percent of review authors were women, while fifty-three percent were men, and most authors were either affiliated with institutions in the European or American regions. None were primarily affiliated with institutions in Africa or low-income countries.

While most RCTs reported gender or sex of participants, only half reported race or ethnicity. No RCTs reported place of residence, occupation, socioeconomic status (SES), or the social capital of participants.

The authors recommend that:

• Authors of primary research should seek diverse participants during recruitment to avoid results that may mask potential benefits or harms to certain groups. By considering whether evidence synthesis of primary study participants are representative of the population with glaucoma, clinicians and policymakers can then make judgements about whether intervention benefits apply equally to a population
• Systematic reviews could consider planning subgroup analyses when PROGRESS factors (a way to analyse health equity) are available in primary research, or where they are not they should try to describe populations according to the PROGRESS framework
• Authors of systematic reviews could include population representation in the summary of recommendations in their paper and discuss generalisability when study populations are not representative
• Journals with the aim of addressing health inequities may consider endorsing the Consolidated Standards of Reporting Trials equity extension for RCTs, and Strengthening the Reporting of Observational Studies in Epidemiology equity for observational studies
• Efforts to promote diversity and inclusion in research authorship and fostering collaboration with researchers and organisations from diverse backgrounds is essential

Overall, the study underscores the need for improved guidance and implementation of tools to incorporate health equity when conducting systematic reviews on glaucoma. The authors identified poor sociodemographic reporting and geographic representation in glaucoma RCTs, including race and ethnicity, potentially limiting the generalisability and applicability of interventions to populations experiencing inequities and people from low-income countries.

Publication

Bondok M, Dewidar O, Al-Ani A et al. Inequities in glaucoma research: an analysis of Cochrane systematic reviews and randomized trials. Journal of Clinical Epidemiology. May 2025. https://doi.org/10.1016/j.jclinepi.2025.111717