Causal Pathway Modelling of Barriers to Glaucoma Treatment Adherence in Northern Nigeria Using a Structural Equation Framework

Non-adherence to glaucoma medication and follow-up schedules is the primary driver of preventable blindness among diagnosed glaucoma patients in Nigeria. Despite extensive descriptive literature on barriers to adherence, causal pathway models that illuminate the relative contributions of individual, interpersonal, and health system factors remain absent from the Nigerian context. This study develops and empirically tests a structural equation model (SEM) of barriers to glaucoma treatment adherence among patients in Sokoto, Katsina, Kano, and Jigawa States in the North West geopolitical zone. A longitudinal mixed-methods design will be employed, beginning with 25 in-depth interviews and four focus group discussions to generate locally grounded theoretical constructs, followed by a cross-sectional survey of 800 glaucoma patients to test the model. SEM analysis using AMOS will examine direct and indirect pathways among variables including health literacy, trust in healthcare providers, medication cost, travel distance, social support, and adherence outcomes. The study will produce a validated causal adherence model applicable to glaucoma programs in low-income settings. Findings will be submitted to the Federal Ministry of Health's blindness prevention unit and international partners for integration into health system strengthening frameworks. This research constitutes an original theoretical contribution to the chronic disease adherence literature in ophthalmology and optometry for northern Nigeria. Keywords: glaucoma adherence, structural equation modelling, causal pathways, northern Nigeria, health system barriers