PURPOSE:

To evaluate the relationship between glaucoma medication usage and dry eye using a Taiwan nationally representative sample.

METHODS:

We identified patients with glaucoma diagnoses (ICD-9-CM [International Classification of Diseases, Ninth Revision, Clinical Modification] codes 365) from Taiwan claims data. The study group included 2065 glaucoma patients with newly diagnosed dry eye (ICD-9-CM code 375.15) identified during 2000 and 2011. The control subjects were 8260 glaucoma patients without dry eye who were frequency matched for age, sex, and the year of the index date. The following variables were considered: sex (male/female) and age (12 to 34 years, 35 to 49 years, 50 to 64 years, and ≥ 65 years). Six available glaucoma drugs in Taiwan were analyzed, namely, prostaglandin analog, β-blocker, carbonic anhydrase inhibitor, α-agonists, pilocarpine, and combination drugs. Univariate and multivariate unconditional logistic regressions were used to estimate the effects of glaucoma treatment and comorbidities on the risk of dry eye as indicated by odds ratios (ORs) with 95% confidence intervals (CIs). Further analysis was performed to assess the dose-response effect on the risk of dry eye according to the cumulative number of different types of glaucoma medications used.

RESULTS:

Among the 2065 dry eye case patients, 63.3% were female and 48.9% were aged 65 years and older. After adjusting for potential confounding factors, an increased risk of dry eye was observed for all glaucoma medications (prostaglandin analog: adjusted OR, 1.48; 95% CI, 1.30 to 1.69; β-blocker: adjusted OR, 1.57; 95% CI, 1.35 to 1.83; carbonic anhydrase inhibitor: adjusted OR, 1.38; 95% CI, 1.20 to 1.59; pilocarpine: adjusted OR, 1.19; 95% CI, 1.07 to 1.32; combination drugs: adjusted OR, 1.32; 95% CI, 1.09 to 1.58) with the exception of α-agonists. The adjusted OR of having dry eye increased with the number of glaucoma medications used. Similar trends were observed for both female and male subjects.

CONCLUSIONS:

An increased number of glaucoma medications used may increase dry eye risk, particularly in subjects who use more than two types of glaucoma medications and in female subjects. Clinicians should be cautious when prescribing medications for glaucoma patients.