Comparability of icare pro rebound tonometer with goldmann applanation and noncontact tonometer in a wide range of intraocular pressure and central corneal thickness

Purpose: To evaluate the agreement between the reading values of the Goldmann applanation tonometer (GAT), Icare Pro rebound tonometer (IRT) and noncontact tonometer (NCT) in glaucoma patients. Methods: This cross-sectional study comprised 292 eyes of 292 patients selected from a glaucoma outpatient clinic. The intraocular pressure (IOP) was measured sequentially, at a 10-min interval each, in the following order: NCT, IRT and GAT. The central corneal thickness (CCT) was measured using Pentacam HR before the IOP measurements. Results: The mean IOPs measured by the GAT, NCT and IRT were 20.17 +/- 6.73 mm Hg (range: 4-48), 19.77 +/- 6.88 mm Hg (range: 3-46) and 19.30 +/- 5.15 mm Hg (range: 7.30-44.5), respectively. The correlation coefficients of the GAT and IRT, NCT and IRT, and GAT and NCT measurements were r(2) = 0.673, r(2) = 0.663 and r(2) = 0.938 (all p <0.001), respectively. The IRT tends to overestimate in the low GAT-measuredIOPs, whereas it underestimates in high GAT-measured IOPs. The measurements of all 3 devices were also correlated with the CCT at a statistically significant level (GAT: r(2) = 0.063, NCT: r(2) = 0.063, IRT: r(2) = 0.058). Conclusion: The agreement between the IRT and GAT measurements is higher in the IOP range of 9-22 mm Hg, whereas significant discrepancies occur as the IOP deviates from normal values. The variability of the IRT and GAT measurements over a wide range of CCT is minimal.