Health Systems Analysis of Eye Care Service Integration into Primary Healthcare in Nigeria: Evidence from Four States Using a Realist Evaluation Framework

The integration of eye care into Nigeria's primary healthcare (PHC) system has been a policy aspiration since the National Eye Health Policy of 2005, but systematic evidence on the mechanisms, contexts, and outcomes of such integration efforts is lacking. This study applies a realist evaluation framework to analyze how, for whom, and under what contextual conditions eye care integration into PHC works in four purposively selected states: Ondo (South West), Taraba (North East), Delta (South South), and Niger (North Central). The realist evaluation will unfold in four stages: systematic scoping of existing program theories for PHC eye care integration; hypothesis generation from stakeholder interviews with 80 informants including health ministry officials, PHC managers, optometrists, and community health officers; quantitative outcome measurement from routine health management information system data on eye care service coverage; and realist synthesis to produce context-mechanism-outcome configurations. The study will produce an original realist program theory for PHC eye care integration in Nigeria, providing a nuanced understanding of the enabling and constraining mechanisms. Findings will be submitted to the Federal Ministry of Health's PHC development board and WHO Nigeria country office to inform policy reform and implementation science for eye health systems strengthening. Keywords: health systems, primary healthcare integration, eye care, realist evaluation, Nigeria