In the treatment of any chronic disease, even the most effective medical therapies cannot achieve optimal success without patients’ co-operation with their prescribed regimens. Patient behaviors, outlooks, and circumstances that lead them to not take prescribed medications are still poorly understood. Such behaviors are probably the result of a complex interplay of many factors that are not easily generalized. What has been commonly referred to as patient compliance can be more accurately described as adherence—the degree to which a patient follows the instructions to take a prescribed treatment during a defined period of time.1 Persistence represents a measure of the time until the patient first discontinues a medication.1 Patient adherence and persistence represent a pervasive problem in the care of patients with glaucoma. Although glaucoma is a major cause of blindness worldwide, the typical course of the disease—a chronic process that is initially asymptomatic—appears to set the stage for suboptimal patient adherence and persistence. Patients with glaucoma are largely not reminded by the disease process itself of the importance of taking medications as prescribed. Indeed, in the care of patients with glaucoma, adherence and persistence rates are not as good as one would hope. And poor adherence to medications can lead to worsening disease.2,3 Moreover, ophthalmologists are not great detectors of non-adherence, with one large study finding that approximately one-fifth of patients had non-adherence undetectable by their physician.4,5 Thus, non-adherence represents a major obstacle in the effective treatment of this sight-threatening condition.
An emerging body of evidence examining factors that influence adherence is providing greater insight into the complexities surrounding why patients have difficulty with adhering to glaucoma therapy and why doctors are poor at detecting this. In this article, we review methods of measuring adherence and persistence, and discuss some of the predominant barriers to adherence and possible strategies to improve it.
Measuring Adherence and Persistence
How does one really know whether a patient is taking a medication as prescribed? Detection of adherence in the clinical setting most commonly uses patient self-reporting in some form or another. When determining adherence in larger cohorts, self-reporting through interviews or questionnaires is a simple method, but also one that has several weaknesses. Self-reports are affected by selection bias and recall bias, and will reflect only the patients who submit to them.2 Those who fail to attend follow-up appointments are excluded from such measurements.2
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