Researchers in a recent study created a predictive model of nonadherence to topical intraocular pressure (IOP)-lowering medications for glaucoma.

Patients with glaucoma who do not adhere to topical IOP-lowering medications could worsen their symptoms, which could potentially lead to vision loss and increased costs, according to a study published by the Journal of Managed Care & Specialty Pharmacy.

Information from the Humana Research Database was used to collect information such as medical and pharmacy claims, as well as data from 73,256 patients age between 65 and 89 years enrolled in Medicare Advantage Prescription Drug (MAPD) plans through Humana. All patients included were prescribed at least 1 IOP-lowering medication between January 2011 and September 2012.

Researchers analyzed factors such as age, gender, race, and geographic location, along with clinical characteristics and pharmacy-based measures. A patient was deemed nonadherent to treatment if they filled less than 292 days of medication over the 12-month period.

Researchers found that 50.9% of patients were adherent to their treatment, although certain types of drugs had lower adherence, such as alpha agonists (39%). Adherence was also increased in continuing users (59%) compared with patients who were not previously treated (33%).

The researchers found that factors that influence adherence were:
  • use of mail or retail to obtain prescriptions
  • new or continuing users
  • gender
  • pre-index medical costs
  • age
  • pharmacy costs
  • having a low-income subsidy
  • glaucoma surgery prior to the study
  • diagnosed with open-angle glaucoma by an ophthalmologist
  • geographic location
Patients who received their prescriptions by mail (OR = 2.68; 95% CI = 2.57-2.79) and those who were new users (OR = 2.48; 95% CI = 2.37-2.60) were the most likely to be nonadherent, according to the study. Adherent patients were also likely to be older, had prior glaucoma surgery, were diagnosed with the condition, had higher pharmacy costs, lived in the South, and received a low-income subsidy.

The researchers believe that other health plans could potentially replicate this model to predict nonadherence for MAPD plan patients, the study concluded.