beta Blockers for glaucoma and excess risk of airways obstruction: population based cohort study

Abstract
We used the Mediplus database to identify patients with no previous diagnosis of airways obstruction. We defined exposed patients as patients who had used ophthalmic topical β blockers for the first time in the period 1993-7. Unexposed patients were randomly selected (loosely matched by age and sex to exposed patients). For validation we inspected a random sample of 40 full longitudinal records of exposed and unexposed patients.