Medication Adherence

Daily medication adherence was measured using MEMS caps (Aardex), which electronically registered the date and time at which the bottle was opened. The MEMS caps recorded data during the implementation phase of adherence,15 which follows treatment initiation and describes the extent to which actual dosing corresponded to prescribed dosing. Patients were given 1 MEMS device for each prescribed ocular hypotensive medication and were instructed to place the eye drop bottle in the MEMS bottle after each instillation. This method was used previously to assess adherence in patients with glaucoma.13 ^, 16 We labelled the MEMS devices with the name of each medication, and the research coordinator verified that the correct medication was in the correct MEMS device at each study visit. Patients were told that the MEMS caps recorded the date and time at which the bottle was opened and were instructed to use the eye drops as usual. The MEMS caps were not equipped with a liquid crystal display, and patients did not receive daily feedback on adherence. The data were downloaded from the MEMS caps at each study visit using a MEMS universal serial bus near-field communication reader, which allows for seamless data transfer from the MEMS caps to the secure web-based MedAmigo platform. When a study visit was missed, the MEMS device continued to monitor adherence and the data were downloaded at the next study visit. Although study visits were missed during the pandemic, all but 4 patients had returned for a visit when the dataset used in this study was assembled.

For each patient, a profile was created in MedAmigo that included the number of MEMS caps assigned, the medication regimen associated with each cap, and regimen changes. This information allowed MedAmigo to translate the raw data downloaded from the MEMS caps into percent adherence. Only 2 patients underwent a change in regimen during the study period. One patient was excluded because of a clinical decision to stop ocular hypotensive therapy in favor of surgery. The other patient underwent a change in medication class and was excluded to avoid introducing regimen change as a confounding variable. Daily adherence was defined as

The 24-hour period that defined 1 day was set arbitrarily to start at 3 am and to end at 2:59 am to minimize the impact of variability in bedtime hour (e.g., if a patient instilled a bedtime dose at 12:25 am, this dose would be counted even though it was technically obtained on the next day). Additional instillations were excluded from the calculation, but no penalty was applied. Penalties also were not applied for doses obtained outside the prescribed time frame (e.g., we did not apply any penalization for an eye drop instilled at 3 pm that was prescribed to be taken in the morning). When 2 or more medications were prescribed, an overall percent adherence score was calculated by averaging the mean adherence for each medication.