Reaching the unreached: Task-shifting diabetic retinopathy screening in urban slums of low- and middle-income countries.

Diabetic retinopathy (DR) is a leading cause of preventable blindness, with the highest burden falling on populations living in urban slums and peri-urban settlements in low- and middle-income countries. These communities often remain outside the reach of conventional health systems due to systemic neglect, migratory lifestyles, and fragile infrastructure. Traditional facility-based screening models are often inaccessible, underscoring the urgent need for decentralized, community-embedded solutions. This review synthesizes global evidence on community and allied health worker (CAHW)-led DR screening initiatives in urban slum contexts, drawing from 22 studies conducted across Asia, Africa, Latin America, and Oceania. In addition, field experience from a DR screening program in Dharavi, Mumbai, one of Asia's largest informal settlements, is included to illustrate operational realities. Findings highlight the transformative potential of task-shifting DR screening responsibilities to CAHWs, many of whom are recruited from the communities they serve. These workers effectively carried out tasks including health education, visual acuity screening, portable fundus photography, referral navigation, and digital data management. With structured training and supervision, CAHWs were found capable of taking on responsibilities conventionally reserved for ophthalmic professionals. Their cultural familiarity and embedded presence also enabled them to overcome key barriers such as distrust, mobility, and language, improving screening uptake and follow-through in underserved populations. Despite clear benefits, challenges persist. Programs often lack standardized competency frameworks, adequate incentives, digital tools, and integrated referral systems. Addressing these gaps is essential for sustaining impact.