It is difficult to estimate what percentage of patients with glaucoma fail to take their medications as prescribed, primarily because we lack a foolproof method of detecting noncompliance. Published studies report noncompliance rates of 28% to 59% among glaucoma patients.2-7'13-15 The large range can be attributed to differences in the definitions of compliance used and in the measurement techniques employed. Rather than classifying patients as either compliant or noncompliant using an arbitrary criterion, it may be more informative to measure the level of compliance (adherence). One study used an electronic monitor to measure compliance to a treatment regimen of pilocarpine taken four times daily.10 Monitor data indicated that patients administered a mean ± standard deviation of 76% ± 24.3% of prescribed doses. The same patients reported taking a mean ± standard deviation of 97.1% ± 5.9% of their doses. These data indicate that noncompliance is common and support the belief that patients who admit noncompliance are truthful, while patients who report good compliance may or may not be truthful.
In recent years, researchers have utilized large databases from Medicare, health plans, or insurance companies to study persistence with medication. A retrospective cohort study using health insurance claims data of 5,300 newly treated glaucoma or glaucoma-suspect patients found that persistence decreased over time and was affected by the type of glaucoma medication used.16 Within 6 months of initiating therapy, nearly half of the patients who filled a prescription discontinued all topical ocular hypotensive medication. In addition, only 37% of these individuals continued to fill the prescription during the subsequent 3 years. Other studies report
Table 14.1 Improper Spacing of Dosing Interval3
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