Glaucoma patients with comorbid conditions have a higher medication burden which, according to this study, may contribute to declining adherence to drops over time. To keep these patients on track, researchers suggest integrating glaucoma treatment into comprehensive chronic disease management plans. Photo: Getty Images.

Getting glaucoma patients to adhere to their drop regimens is a perennial challenge for eyecare providers, with noncompliance rates ranging from 30% to 50%. Studies have pinpointed numerous barriers to glaucoma medication adherence, such as high out-of-pocket costs, discomfort or difficulty instilling drops, simple forgetfulness and insufficient glaucoma-related knowledge, to name a few. A recent study published in American Journal of Ophthalmology identified another barrier to add to this list: the presence of comorbidities. Its authors found that the higher medication burden in glaucoma patients with comorbid conditions may lead to reduced priority for glaucoma treatment, given that glaucoma often has less prominent symptoms.

To help determine the impact of comorbidities on glaucoma drop adherence, data was gathered from National Health Insurance claims on 50,408 patients with newly diagnosed glaucoma who were followed for up to five years. Researchers used a metric called the Deyo-Charlson Comorbidity Index to identify patient comorbidities and another known as the medication possession ratio (MPR) to assess adherence, calculated by dividing the total number of days a patient had a supply of glaucoma medication by 365.

The researchers found that compared with people without comorbidity, patients with at least one comorbidity exhibited higher MPR (equating to better medication adherence) in the first two years following glaucoma onset. However, in the long term, these patients had significantly lower medication adherence, specifically in the fourth and fifth years after glaucoma onset.

In their paper on the study, the authors offered a possible explanation for the observed pattern of declining adherence among patients. “Individuals with higher comorbidity scores are more likely to visit healthcare facilities for the management of their comorbidities,” they wrote. “More frequent physician visits are associated with higher medication adherence. However, in the long term, the burden of managing multiple chronic diseases may become increasingly high.”

Aligning with this theory, the data also revealed that the degree of nonadherence increased with the number of comorbidities. “Patients with a higher number of comorbidities had a significantly lower probability of having persistent high adherence over the next five years after glaucoma onset,” the researchers wrote in their paper. By year five, they reported that patients with more than four comorbidities displayed nearly a 12% reduction in glaucoma drop adherence.

“Managing multiple comorbidities necessitates complex treatment plans and multiple medications, increasing the complexity of the medication regimen,” which can make adherence more difficult, the authors explained. They add that some comorbidities are clinically dominant (e.g., end-stage renal disease) or highly symptomatic (e.g., chronic pain), which “may divert attention away from glaucoma, which typically lacks immediate fatal consequences or clear symptoms.”

To help improve medication adherence among glaucoma patients with comorbidities, which is crucial for achieving positive outcomes, the study authors emphasize “the importance of integrating glaucoma treatment into comprehensive chronic disease management plans.”

Hou CH, Pu C. Long-term effect of systemic comorbidity on glaucoma medication adherence. Am J Ophthalmol. January 24, 2024. [Epub ahead of print].