New Non-contact Tonometer HNT-1P Reliability: Comparing Intraocular Pressure, Central Corneal Thickness, and Corrected Intraocular Pressure

Purpose: To assess the reliability of a new non-contact tonometer, HNT-1P, by comparing its intraocular pressure (IOP), central corneal thickness (CCT), and corrected IOP (cIOP) measurements with the IOP measured by Goldmann applanation tonometry (GAT), the CCT measured with ultrasound pachymetry (USP), and the cIOP derived from GAT IOP and USP CCT. Methods: A total of 120 eyes of 65 healthy or glaucoma suspects were included in this study. The IOP was measured with the HNT-1P and GAT. The CCT was determined using the HNT-1P and USP. The IOP measured with GAT was corrected according to the CCT measured by USP. The correlations of the measurements obtained with the various instruments were evaluated using Pearson's correlation coefficient, and the agreement was assessed using Bland-Altman plots. Results: The average IOP measured with the HNT-1P and GAT was 14.8 +/- 5.1 mmHg and 15.6 +/- 5.2 mmHg, respectively, and the correlation coefficient between the two IOP measurements was 0.964 (p < 0.001). The mean CCT was 553.5 +/- 27.4 mu m using the HNT-1P and 550.6 +/- 26.3 mu m using USP, and the correlation coefficient between the two measurements was 0.913 (p < 0.001). The average cIOP was 14.6 +/- 5.0 and 13.4 +/- 6.5 mmHg according to the HNT-1P and GAT, respectively, and the correlation coefficient between the two corrected measurements was 0.956 (p < 0.001). Bland-Altman plots showed a high degree of agreement between the HNT-1P measurements and those of the other devices. Conclusions: The new non-contact HNT-1P tonometer provided reliable IOP, CCT, and cIOP measurements when compared with GAT and USP. HNT-1P could therefore be used clinically for reliable and accurate measurements of the IOP, CCT, and cIOP.