A new paper published in the Journal of Clinical Epidemiology has found that systematic reviews and primary research in cataract, the leading cause of avoidable blindness globally, do not take into account factors that could make them more equitable for the most vulnerable people affected.

The study, undertaken by researchers from the International Centre for Eye Health, looked at Cochrane Eyes and Vision systematic reviews and the recent primary research studies they are based on. Systematic reviews aim to collate existing studies within a healthcare topic to provide summaries and compare findings, and Cochrane are a leading provider of these reviews.

Vision impairment from cataract is distributed unequally, with disadvantaged populations disproportionately affected. Looking at factors associated with disadvantage in healthcare, such as location, socioeconomic status and disability, the team found that the majority of reviews and primary papers did not assess these factors when choosing the question to be studied, the populations to study, or the effects of interventions on subgroups within populations.

Considering equity in healthcare is extremely important to ensure that all groups affected by an illness receive the benefits of a healthcare intervention. In some cases, healthcare interventions may have a negative impact on equity. While gender/sex was often taken into account when describing participants of the studies, the effect on differences in these groups was not assessed further. Specific sub-analyses that could assess the effect of the studies on other population groups, such as race/ethnicity, were very rarely or never done.

Despite the burden of cataract being predominantly experienced by people in low and middle-income countries (LMICs), an LMIC author led only two of the sixty-two primary studies and one of the twenty-three reviews assessed by the team.

The study highlights the need for improved inclusion of LMIC authors in research teams and the consideration of equity factors when undertaking research to improve the effectiveness of cataract interventions for all.