Comparison of intraocular pressure measurements using Goldmann tonometer, I-care pro, Tonopen XL, and Schiotz tonometer in patients after Descemet stripping endothelial keratoplasty

PURPOSE Post-Descemet stripping endothelial keratoplasty (DSEK) patients are prone for intraocular pressure (IOP) elevations and glaucoma. Corneal characteristics influence various IOP measuring devices in various ways. The aim of this study was to evaluate the agreement between four different IOP measuring devices: Goldmann applanation tonometer (GAT), I-care pro, Tonopen XL, and Schiotz tonometr in patients who underwent DSEK. METHODS This was a prospective comparative study using a convenience cohort of post-DSEK patients with compact grafts. Post-DSEK patients had IOP measured using GAT, I-care Pro, Tonopen XL, and Schiotz tonometer. Measurements were compared and agreement assessed. Wilcoxon signed-rank test was used for comparison of means as variables did not show a normal distribution. Bland-Altman plots were used for assessing agreement. RESULTS Thirty eyes of 24 patients were included in the study. Mean time from DSEK surgery was 25.31 ± 13.05 months. Mean IOP with GAT, I-care pro, Tonopen XL, and Schiotz tonometer was 13.99 ± 3.76, 13.92 ± 3.36, 13.31 ± 3.89, and 12.83 ± 4.07, respectively. GAT, I-care pro, and Tonopen XL had similar mean IOP measurements (P = 0.135 and P = 0.551, respectively), while Schiotz tonometry measurements were higher (P = 0.046). Bland-Altman plots show good agreement between GAT, Tonopen XL, and I-care pro. GAT and Schiotz tonometry show less agreement, with large variations in the differences of measured IOP. CONCLUSIONS IOP measurements in post-DSEK patients showed good agreement between GAT and either Tonopen XL or I-care pro. Schiotz tonometer has large variations in this patient group. IOP measurements and IOP difference between devices were not dependent on central corneal thickness.