Latanoprost treatment differentially affects intraocular pressure readings obtained with three different tonometers

Purpose To evaluate the apparent intraocular pressure (IOP) change observed after treatment with latanoprost in naive eyes of patients with primary open-angle glaucoma (POAG) or ocular hypertension (OHT) using Goldmann applanation tonometer (GAT), ocular response analyzer (ORA) and Corvis ST tonometry. Methods Prospective observational cohort study. One eye from each of 59 newly diagnosed patients with POAG or OHT in our institution was analysed. IOP readings obtained using GAT, ORA and Corvis at baseline and after a 3-month period of treatment with latanoprost were compared. Additionally, pre- and post-treatment biomechanical corneal parameters provided by the Corvis tonometer were analysed. Results There was no statistically significant difference between the apparent treatment-induced IOP reductions when GAT and ORA were compared (p > 0.05). In contrast, the treatment-induced IOP reduction recorded using the Corvis tonometer was significantly smaller compared to the apparent IOP reduction observed with GAT and ORA (p = 0.0001 for both comparisons). With respect to biomechanical corneal properties, statistically significant changes were found after 3 months of treatment with latanoprost for the first corneal applanation time (AT1) (p = 0.001), second corneal applanation time (AT2) (p = 0.001) and deformation amplitude (DA) (p = 0.0003). Conclusion Following a 3-month course of latanoprost, the apparent treatment-induced IOP reduction in previously naive patients with POAG or OHT differed depending on the tonometer used. Certain corneal biomechanical parameters assessed using Corvis ST exhibited a significant change. The ocular hypotensive effect of prostaglandin analogues may be overestimated when chronically treated patients are measured using GAT or ORA.