Sir,

We read this paper with interest. The study is an economic evaluation of topical antagonists and prostaglandin analogues for the treatment of glaucoma. It uses a Markov model to explore costs, and mentions risk of blindness, glaucoma subtypes and makes the assumption that health status will remain the same. Outcome measures also discuss visual field progression. The study suggests that topical antagonists are the cost-effective model in the United Kingdom.

This may or may not be the case, but the study does not provide adequate evidence to address this question. Specifically, there is no consideration of systemic side effects. There are compelling data that topical antagonists are associated with an increased risk of airways obstruction, necessitating drug treatment and further evidence that more serious side effects occur.1, 2, 3 In an earlier study, the number needed to harm with topical antagonists was calculated to be one in 23 patients.2 Without considering costs incurred by the health-care economy as a whole, such studies have very limited application.