Determinants of adherence to glaucoma medical therapy in a long-term patient population.

Purpose: Estimate patient adherence to glaucoma medications and identify potential determinants of nonadherence.
Design: Descriptive study.
Methods: Two hundred patients with open angle glaucoma, ocular hypertension, or glaucoma suspects were interviewed regarding their glaucoma and its treatment and their charts were reviewed. Their ophthalmologist completed a brief assessment form. Drug utilization data were extracted from the provincial drug program database. Patients were defined as adherent if they filled at least 75% of the prescribed medication necessary for their treatment.
Results: Data were available for 181 patients. About 62.9% were female and the mean age (+/-SD) was 75.1+/-8.8 years. The mean number of years of glaucoma treatment was 10.7+/-9.3. Self-reported treatment adherence was 88.3%. On the basis of the drug database, the proportion of patients who were adherent to treatment was 71.8%. According to physicians, 74.6% of patients were adherent. Among patients considered by physicians as nonadherent, 71.1% (32/45) were adherent and among patients predicted as adherent, 72.1% (98/136) were adherent. There was no significant difference in adherence according to age, sex, education, and income. However, patients using fewer agents (P=0.041), who were widowed (P=0.041), or who lived alone (P=0.042) were more adherent. Patients using prostaglandins analogs or beta-blockers were more adherent than those using carbonic anhydrase inhibitors (P<0.05).
Conclusions: Fewer medications, use of prostaglandin analogs or beta-blockers, living alone, and being widowed were significantly associated with adherence. Physicians were unable to significantly predict which patients are adherent.