The relationship between intraocular pressure (IOP), central corneal thickness (CCT) and the manifestation of glaucoma is a complex one. It’s long been known that you need to take into account CCT when measuring patients’ IOP; the smaller a patient’s CCT, the greater their chance of developing primary open-angle glaucoma (POAG) (1),(2). But with research showing topical anti-glaucoma therapies can thin patients’ corneas (3),(4), the question people are asking is: how might prostaglandin analog (PGA) treatment affect the accuracy of IOP monitoring with Goldmann Applanation Tonometry (GAT)?

A Montreal-based team of researchers decided to investigate (5). They recruited 35 patients (70 eyes) with POAG who were on chronic topical PGA therapy (mean treatment duration, 3.99 years) into a prospective, 12-week interventional case-control study. Each patient ceased PGA therapy for a six-week period in one eye (the better, “study eye”), before recommencing therapy afterwards (Figure 1). The contralateral eye continued to receive therapy throughout the study, and acted as control.