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

Abstract

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.

Introduction

Reaching unreached urban populations is a persistent challenge in global diabetic eye care. Diabetic retinopathy (DR), which affects over 103 million people globally, is a leading cause of preventable blindness, disproportionately burdening underprivileged populations living in urban slums and peri-urban informal settlements.[1] These communities, often excluded from structured health systems, face compounding barriers including high diabetes prevalence, poor health infrastructure, and delayed access to eye care services. The rapid pace of global urbanization has intensified this challenge, contributing to the unchecked growth of underserved urban populations living in dense, informal, and often migratory conditions. Despite being geographically close to urban hospitals and health centers, slum residents are functionally distant due to socioeconomic exclusion, infrastructural neglect, and systemic invisibility in national health planning (UNHABITAT 2008). The World Health Organization’s World Report on Vision (2019) and its integrated people-centered eye care (IPEC) framework explicitly call for innovative, inclusive strategies to extend eye care to marginalized populations. These global frameworks underscore the urgency of reaching underserved urban communities with models that are embedded, equitable, and scalable. As emphasized in IPEC, “eye care interventions should be delivered in a way that is coordinated around people’s needs and provided in the most accessible settings possible” (WHO, 2019), making a strong case for community-based approaches in urban slums.

These communities are typically migratory in nature, with individuals lacking permanent addresses, consistent medical records, or sustained healthcare contact. Such fragmentation disrupts continuity of care and exacerbates the risks of unmonitored diabetic complications.[2]

To address these gaps, community-embedded strategies are increasingly advocated. One such approach is task-shifting or task substitution – the rational redistribution of health tasks from highly specialized professionals to trained nonspecialist health workers. In the context of DR screening, this means delegating specific roles such as visual acuity testing, health education, fundus imaging, and referral coordination to community and allied health workers (CAHWs), including community health workers (CHWs), auxiliary nurse midwives, and ophthalmic technicians. Task-shifting not only alleviates workforce shortages but also improves coverage and access by engaging personnel from within the community itself. These workers are often better positioned to overcome cultural and linguistic barriers, build trust, and deliver care in a manner that is acceptable and accessible to underserved populations. This model also aligns with the core principle of “from the community, for the community,” and supports continuity of care, especially critical in transient and low-literacy populations.

Importantly, the role of CAHWs in DR screening is dynamic. With structured training and mentorship, these workers can evolve from outreach and counseling roles to performing technical tasks such as smartphone-based fundus photography and tele-ophthalmology coordination.[3] However, despite their growing importance, CAHW-led models for DR screening remain underutilized and poorly integrated into national health systems.

This review synthesizes global and regional evidence to examine the effectiveness of CAHW-led, task-shifted DR screening models in urban slums and peri-urban communities. It draws on policy frameworks, including the World Health Organization’s World Report on Vision (2019) and the IPEC strategy. By exploring the evolving competencies of CAHWs and the structural enablers that support their integration, this study outlines an equity-oriented, scalable pathway to DR screening for vulnerable urban populations.

Methodology

We conducted a narrative review to explore the roles, evolving competencies, and implementation strategies of CAHWs in DR screening within urban slums and peri-urban under-resourced settings. A structured search was performed across five major databases – PubMed, Scopus, Web of Science, Google Scholar, and grey literature sources, including institutional reports and WHO publications, for studies published between January 2010 and December 2024.

Search terms included combinations of keywords and MeSH terms such as “diabetic retinopathy” AND “community health workers,” “diabetic eye screening” AND “urban slums” OR “peri-urban,” “task-shifting” AND “eye care,” “allied health workers” AND “screening” AND “diabetes,” and “low-resource settings” AND “teleophthalmology” OR “fundus photography.” Boolean operators (AND, OR) were used to refine and expand the search scope.

Studies were eligible for inclusion if they were published in English, focused on CAHW-led DR screening efforts in urban or peri-urban low- and middle-income countries (LMIC) contexts, and described implementation details such as community mobilization, vision assessment, fundus imaging, or referral coordination. We excluded studies focused solely on rural settings, interventions lacking CHW involvement, or those limited to standalone technological evaluations without a human health resource component. Editorials, opinion pieces, and conference abstracts without primary data were also excluded.

From an initial pool of 250 records, 72 full-text articles were screened after title and abstract review. A total of 22 studies met the final inclusion criteria [Figure 1: Preferred Reporting Items for Systematic Reviews and Meta-Analyses-guidelines]. Data were thematically synthesized, focusing on CAHW cadres, types of tasks shifted, innovations applied (e.g., artificial intelligence [AI]-assisted imaging), program outcomes, and alignment with national or WHO eye care frameworks. Findings were categorized under key themes, including roles and competencies, regional implementation strategies, enablers and barriers, and health systems integration.

Figure 1.

Preferred Reporting Items for Systematic Reviews and Meta-analyses flow diagram illustrating study selection process

Thematic Synthesis

Community and allied health worker roles and evolving competencies

Across the studies reviewed, CAHWs were shown to function as frontline educators, screeners, and referral navigators in DR programs, significantly contributing to early detection and patient engagement in under-resourced urban communities. In Mumbai’s Dharavi slum, CAHW-led efforts increased screening uptake from 38% to 57% following structured community mobilization and outreach.[4] Comparable models in Kenya and Bangladesh reported improved adherence to DR screening referrals when CAHWs were actively involved in patient navigation and education.[5,6]

Conventionally, tasks such as basic vision assessment and fundus photography were confined to ophthalmic specialists or mid-level providers. However, increasing evidence shows CAHWs are now being trained to conduct these tasks using portable imaging devices, particularly smartphone-based fundus cameras.[5,7] This shift represents a meaningful expansion of community workforce capacity and exemplifies the principle of task-shifting in eye care.

Drawing on field-based experience from a DR screening initiative in urban slums of Mumbai, a dynamic evolution in CAHW responsibilities was observed. Initially limited to door-to-door diabetes awareness and general counseling, CAHWs gradually took on expanded responsibilities – including organizing screening camps, administering structured risk assessment questionnaires, and coordinating referrals.[3] With progressive mentorship and structured technical training, several CAHWs began independently operating handheld fundus cameras and managing image transmission for teleophthalmology review.[8]

Innovative implementation models by region

Regional strategies for task-shifting DR screening to CAHWs vary but consistently demonstrate promise in improving service delivery [Table 1]:

Table 1.

Community and allied health worker-led diabetic retinopathy screening models: Regional strategies and policy pathways

Region	Representative countries	CAHW cadres	Service strategy	Key policy levers
Asia[3,4,5,16,17,18]	India, Bangladesh, Pakistan	CHWs, ASHAs, ANMs, LHWs, ophthalmic technicians	Community sensitization, door-to-door screening, AI-supported imaging	Integrate DR into NCD packages; standardize CAHW training; expand telehealth
Africa[6,10,11,19]	Kenya, South Africa, Nigeria, Zambia	CHWs, PHC nurses, peer educators	Mobile outreach, integrated PHC-based screening	Formalize CAHW roles; strengthen referral linkages; adopt task-shifting policies
Latin America[7,13,20]	Brazil, Peru	Mid-level technicians, CHWs	AI-based fundus photography, community mobilization	Invest in digital health; subsidize DR services under insurance schemes
Oceania[15]	Fiji	CHWs, peer-support volunteers	Peer-led education, localized referral support	Incentivize volunteers; embed eye care into primary/community health platforms

CAHW: Community and allied health worker, CHW: Community health worker, ASHA: Accredited social health activist, ANM: Auxiliary nurse midwife, LHW: Lady health worker, PHC: Primary health care, DR: Diabetic retinopathy, NCD: Noncommunicable disease, AI: Artificial intelligence

• South Asia has shown early adoption of mobile DR screening models, including AI-assisted retinal imaging integrated into national blindness control programs. Task-shifting strategies involving Accredited Social Health Activists and ophthalmic technicians are gaining traction in India and Bangladesh[5,8,9]

• Sub-Saharan Africa has piloted task-shifting through CHWs and primary healthcare (PHC) nurses, particularly in Kenya and South Africa. Programs focus on integrating DR screening into existing PHC platforms to improve efficiency and sustainability[10,11,12]

• Latin America, especially Brazil and Peru, has emphasized technology-led approaches such as AI-based fundus photography. While results show improved diagnostic accuracy and referral triage, engagement with local communities and CAHWs remains an area for improvement[7,13,14]

• Oceania, notably Fiji, has deployed CHW-led peer-support models. These have improved community education and referral compliance, although long-term scalability is hindered by limited funding and reliance on volunteer labor.[15]

Barriers to implementation and upscaling

Despite promising outcomes, multiple challenges inhibit the widespread scale-up of CAHW-led DR screening programs:

• Training gaps and inconsistent competencies: Absence of standardized frameworks and refresher training led to variable performance across settings. In India and Pakistan, low DR awareness caused misinformation and screening gaps.[3,4,18] In Africa and Brazil, inadequate training in eye care and image interpretation affected image quality and reduced service uptake[19,21]

• Inadequate incentives and retention issues: Irregular pay, heavy workloads, and lack of formal recognition contribute to CAHW attrition. In Pakistan, South Africa, and Brazil, staff shortages and competing duties limited CAHW capacity to deliver consistent DR screening and follow-up[17,19,21,22]

• Sociocultural constraints: Language barriers, gender norms, and low health literacy hinder CAHW effectiveness. Misconceptions and limited DR knowledge reduced screening uptake in India, while mobility and decision-making constraints limited women’s participation in Pakistan and Bangladesh.[5,11] In Fiji, linguistic diversity further hampered CHW communication efforts[15]

• Weak supervision and referral pathways: Fragmented links to secondary care and a lack of feedback mechanisms weaken follow-up and CAHW motivation. In Pakistan and sub-Saharan Africa, staff turnover, limited equipment, and low confidence in PHC workers hampered screening.[17] In Latin America, financial and staffing shortfalls disrupted referral continuity, straining tertiary centers.[13,20] These challenges underscore the urgent need for better training, resource planning, and integrated referral pathways.

Discussion

As urbanization accelerates across LMICs, urban slums and peri-urban settlements have emerged as hotspots of health inequity. Although physically proximate to urban health infrastructure, these communities remain structurally and socially excluded from formal care systems. In the context of DR, this exclusion contributes to late diagnosis, vision loss, and unnecessary blindness. Traditional facility-based eye care delivery models often fail to reach slum dwellers, particularly in settings where migration, lack of documentation, and informal housing disrupt continuity of care (WHO 2019).

Task-shifting DR screening responsibilities to CAHWs presents a pragmatic, people-centered solution. By enabling trained nonspecialist cadres, such as CHWs, auxiliary nurses, and ophthalmic assistants, to conduct awareness, basic assessments, and even retinal imaging, programs can decentralize care, increase reach, and improve patient adherence. Our synthesis demonstrates that CAHWs are not only capable of fulfilling technical roles when supported by appropriate training but are also uniquely positioned to deliver culturally competent services. This is particularly valuable in slum populations with linguistic diversity, strong local social networks, and varying health beliefs.[4,6,10,15,18]

The capacity of CAHWs to bridge formal health systems and local realities makes them critical to the success and sustainability of DR screening initiatives in urban slums. Their community-embedded roles foster trust, cultural alignment, and continuity of care, particularly important for a chronic, surveillance-dependent condition like DR. This “from the community, for the community” approach enhances service uptake among marginalized and migratory populations often missed by conventional models.[9] Importantly, CAHW competencies are not static; they can evolve through structured training, mentorship, and integration into health system workflows. When effectively empowered, CAHWs serve as trusted health ambassadors, capable of addressing sociocultural barriers and workforce shortages in eye care across underserved urban settings.

This review further highlights the evolving nature of CAHW competencies. Drawing from both literature and field experience, we observed that CAHWs can progressively transition from outreach and education roles to more specialized tasks such as operating handheld fundus cameras, conducting risk stratification, and coordinating referrals. This trajectory mirrors successful task-shifting models in other public health domains, for instance, the use of CHWs in hypertension management programs where they monitor blood pressure and encourage treatment adherence.[23]

Digital tools such as teleophthalmology platforms and AI-assisted image grading systems have played a critical enabling role in expanding task-shifted DR screening models. In multiple programs, CAHWs were trained to capture retinal images using smartphone-based or portable nonmydriatic fundus cameras. These images were then uploaded to cloud platforms for asynchronous review by remote ophthalmologists, significantly improving diagnostic turnaround and reducing the need for on-site specialists.[7,8,13] AI-supported image analysis further streamlined workflows, enabling real-time or near-real-time triaging of referable DR. This allowed CAHWs to rapidly identify high-risk patients, provide immediate counseling, and initiate timely referrals. In Brazil and India, pilot projects demonstrated that community-level screening accuracy improved when AI tools supported frontline image acquisition.[8,14] These technologies not only enhanced CAHW confidence but also strengthened quality assurance in low-resource, high-volume settings. While integration of these tools remains uneven due to digital infrastructure constraints, where implemented, teleophthalmology and AI significantly boosted CAHW performance, accuracy, and program efficiency, validating their role in scalable DR screening models.

However, several barriers hinder the scale-up of such community-led DR screening models. Unlike established frameworks like WHO’s Package of Essential NCD interventions, DR screening lacks global competency guidelines tailored to CAHWs. The absence of such standardization leads to variability in training quality, scope of practice, and service delivery across settings. Furthermore, while digital innovations, such as AI-assisted grading and teleophthalmology, enhance task-shifting potential, their integration remains constrained by infrastructural gaps, regulatory uncertainties, and workforce readiness.[7,8,13]

From a systems perspective, sustaining CAHW programs requires more than technical training. Inadequate financial incentives, unclear career pathways, and inconsistent supervision contribute to high attrition. Embedding CAHWs into formal health workforce strategies, with defined roles, incentives, and supervisory mechanisms, is essential to program durability.

Looking ahead, implementation research should focus on context-specific models for integrating CAHW-led DR screening into national primary care systems, including performance-based remuneration and community co-design mechanisms. Evaluating cost-effectiveness, patient outcomes, and digital readiness will provide a stronger evidence base for policy adoption.

Strengths and limitations

This review is among the first to focus exclusively on community-led, task-shifted DR screening models in urban slums and peri-urban settings across LMICs. It combines evidence from 22 studies with practical field insights from a slum-based program in Mumbai, enhancing both relevance and contextual depth. The use of a thematic synthesis approach and the inclusion of implementation-level insights provide actionable guidance for health planners, policymakers, and global eye health stakeholders. However, as a narrative review, this study does not include formal risk-of-bias assessments or quantitative meta-analysis. Heterogeneity across settings, health systems, and CAHW cadres may limit generalizability. In addition, few studies provided long-term outcome data or cost-effectiveness analyses, which are essential for policymaking and integration into universal health coverage (UHC) schemes.

Policy Implications

To scale and sustain task-shifted DR screening in urban slums, national and local policymakers must prioritize system-level interventions that institutionalize the role of CAHWs. The following actions are recommended:

• Standardize competencies: Develop and adopt national competency frameworks for CAHWs in DR screening, aligned with WHO’s people-centered eye care guidelines. These should outline clear scopes of practice, training protocols, and certification pathways

• Integrate with primary health care and UHC: Embed CAHW-led DR screening within national diabetes and eye care programs as part of UHC. This integration should include referral pathways, follow-up systems, and shared data infrastructure

• Sustainable financing and incentives: Allocate dedicated funding through public health budgets or insurance schemes to support CAHW remuneration, career progression, and digital tools. Performance-based incentives can further improve retention and accountability

• Leverage digital innovation: Support the uptake of teleophthalmology and validated AI-based imaging tools to expand CAHW capacity, particularly in settings with limited specialist availability

• Community ownership and cultural relevance: Promote participatory planning and peer-led outreach strategies that leverage CAHWs’ embeddedness in the community. This enhances trust, counters misinformation, and improves long-term screening adherence.

Policy supports in these domains will not only improve DR detection and treatment among underserved populations but will also contribute to broader goals of health equity, workforce optimization, and prevention of avoidable blindness in LMIC urban settings.

Conclusions

Urban slums and peri-urban communities remain underserved in DR care, despite their growing vulnerability. This review affirms that CAHWs, when adequately trained and supported, can extend DR screening coverage through a task-shifting model tailored to local needs. Their evolving roles, from health education to fundus imaging, demonstrate practical, people-centered solutions to bridge eye care gaps in low-resource urban settings.

To move from isolated success to system-wide impact, CAHW-led screening must be formally embedded within national health strategies, linked to primary care, and supported by clear competency frameworks, digital tools, and sustainable financing. Advancing this model is not only cost-effective but also essential for achieving equity and reducing avoidable blindness in rapidly urbanizing LMICs.

Conflicts of interest

There are no conflicts of interest.

Funding Statement

Nil.