Psychosocial Determinants of Glaucoma Treatment Adherence: A Longitudinal Study Extending the Health Belief Model

Purpose: Adherence to glaucoma treatment remains a critical challenge in Japan, with nearly half of patients discontinuing treatment within a year. Guided by the Health Belief Model (HBM), this study investigated the psychosocial predictors of treatment adherence and evaluated an extended model incorporating personality traits and optimistic bias. Methods: A two-wave longitudinal online survey was conducted among 2,400 patients aged 40–69 years with early-to-mid-stage glaucoma across Japan (T1: January 2023; T2: October 2023). The measures included glaucoma treatment status, knowledge, doctor–patient relationship, health belief-related variables, social norms, personality traits, and optimistic bias. Structural equation modeling was used to test the predictive validity of the HBM and extended models. Results: Among health belief-related factors, perceived barriers (β = −.31, p < .001) and social norms (β = .18, p < .001) negatively and positively predicted adherence, respectively. Personality and optimistic bias improved the overall model fit, although the variance explained by adherence was modest (12%). The doctor–patient relationship and knowledge indirectly influenced adherence by reducing perceived barriers and enhancing social norms. Perceived severity and self-efficacy were not significant predictors of treatment adherence. Conclusions: Lower perceived barriers and higher social norms were found to predict higher treatment adherence. Perceived severity and self-efficacy were weaker predictors of glaucoma treatment adherence than barriers and social norms. Extending the HBM to include personality and optimistic bias provided an incremental explanatory value. These findings highlight the importance of strengthening doctor–patient relationships and tailoring interventions to individual belief systems to support long-term treatment adherence for glaucoma.