: PRéCIS: Univariate and multivariable models using the Glaucoma Treatment Compliance Assessment Tool (GTCAT) statements identified multiple, patient-specific factors associated with adherence that could be used to inform personalized interventions to optimize glaucoma adherence. PURPOSE: The purpose of this study was to determine the health behavior factors related to glaucoma adherence in patients with self-reported poor adherence. METHODS: A research coordinator used the Chang Adherence Measure and the Morisky Medication Adherence Scale to identify subjects with poor self-reported glaucoma medication adherence and enrolled them in a 3-month study to electronically monitor medication adherence. At enrollment, the coordinator administered the GTCAT. We calculated the percentage of prescribed doses taken over a 3-month period using an electronic dose monitor (AdhereTech). We used Rasch analysis, and univariate and multivariable regression to determine the GTCAT statements that predicted electronically monitored adherence. RESULTS: The mean adherence was 73.8% (SD=21.04%, range: 13% to 100%). Rasch analysis showed that the GTCAT had a good overall fit and no differential bias (Anderson likelihood ratio test >0.05). Multiple GTCAT statements were associated with adherence, which represented increased knowledge, increased cues-to-action, decreased barriers, less depression, and increased self-efficacy (P<0.09 for each). The full GTCAT or a subset of statements had a high association with adherence (R range: 0.44 to 0.51, P<0.005 for all). The GTCAT identified >50% of patients who wanted more education about glaucoma; >68% who did not use reminders; and >40% who reported having difficulty using the eye drops. CONCLUSIONS: The GTCAT identified multiple factors associated with adherence. Clinicians and researchers could use this tool to identify specific barriers to adherence and develop potential interventions to improve adherence.