Long-term glaucoma medication adherence in Finland: a 13-year registry study with clinical outcomes and international cohort comparisons

Background/aims Despite well-known suboptimal adherence to glaucoma medications, the evidence linking adherence to clinical outcomes is limited. We evaluated long-term adherence and clinical outcomes in a large cohort and compared our findings with three recent publications. Methods Using pharmacy dispensing claims of glaucoma medications, 10 769 patients’ refilling data in 2008–2020 were linked to hospital records and national reimbursement data. Clinical data were available for 6802 patients (63%). Adherence was quantified as persistence (time on therapy with 90 day refill gap defined as discontinuation) and implementation (proportion of days covered, PDC). Intraocular pressure (IOP), visual field mean deviation and progression as well as the frequency of procedures were analysed for better and worse eyes in patients with manifest and suspected glaucoma. Results During the median 9-year (IQR, 4–13) follow-up, of the 46% of patients discontinuing therapy at least once, 73% subsequently restarted using medications. Among persistent patients, implementation was high (median PDC 0.93, IQR 0.79–0.98, mean 0.84, SD 0.20) and improved over time. Combining non-persistence with suboptimal implementation, patients were non-adherent for a median 9.5% (IQR, 0–44%) and mean 19% (SD, 22%) of the follow-up time. Suboptimal adherence was associated with male sex, higher IOP and more surgical procedures. Conclusion Despite higher adherence than in previous studies, our study revealed frequent interruptions and resumptions. Similar to international cohorts, suboptimal adherence was linked to higher IOP and more frequent surgery. However, differences in cohort compositions, methodology and reporting indicate a demand for developing standardised protocols in adherence studies.