Evaluation of intraocular pressure measured with Corvis ST tonometry, noncontact tonometry and dynamic contour tonometry

Objective To explore the repeatability of the Corneal Visualization Scheimpflug Technology (Corvis ST) for measuring intraocular pressure (IOP), and compare the results of Corvis ST with the results of noncontact tonometer (NCT) and dynamic contour tonometer (DCT). Methods Ninety-one eyes from 91 healthy subjects were included in this study. All the right eyes were chosen for IOP measurement using Corvis ST, NCT and DCT, respectively, and each measurement repeated three times. The IOP results of three different tonometers were analyzed with ANOVA, and the intraclass correlation coefficient (ICC) was used to evaluate the repeatability of these three methods; Bland-Altman was used to evaluate the consistency of IOP results, and the correlation relationship between the IOP results were analyzed by Pearson correlation analysis. Results The mean values of IOP_Cor, IOP_NCTand IOP_DCTwere (13.39±2.48) mmHg (1 mmHg=0.133 kPa), (13.94±2.32) mmHg and (17.26±2.00) mmHg, respectively. The difference were statistically significant (F=76.949, P< 0.001, ANOVA). Correlation analysis showed that three tonometers measured IOP results had significant correlation between each other (P< 0.001). The Cologne Bach coefficient (Cronbach's α) of IOP_Cor, IOP_NCTand IOP_DCTwere 0.94, 0.91 and 0.94, respectively; and ICC were 0.83, 0.76 and 0.83, respectively. Bland-Altman consistency analysis showed that in group IOP_Corand IOP_NCT, the deviation was (-0.5±1.8) mmHg, IOP_Corand IOP_DCTwas (-3.9±2.1) mmHg, IOP_DCTand IOP_NCTwas (-3.3±2.2) mmHg, the consistency limit intervals were (-4.1- 3.0) mmHg, (-7.9- 0.2) mmHg and (-7.6- 1.0) mmHg, respectively. Conclusion Corvis ST can effectively measure the IOP with good measurement repeatability. The relationship with NCT measurement results shows good consistency, but there still exist differences with DCT measurement results.