Comparison between Corvis and other tonometers in healthy eyes

To determine the agreement of intraocular pressure (IOP) values in healthy eyes among Goldmann applanation tonometer, dynamic contour tonometer, ocular response analyzer and Corvis. Additionally, to study the relationship between their differences with central corneal thickness (CCT) and corneal curvature (CK).

Seventy-six eyes of 76 healthy subjects were examined. Every subject underwent a complete ophthalmic evaluation, a Pentacam scan and three consecutive IOP measurements with each instrument (DCT, GAT, ORA and CST). IOP measurements provided by each device were compared with each other and the differences between them were correlated with morphological parameters obtained by Pentacam (CCT and CK). Statistical analysis was performed using SPSS software, version 18.0.

The mean age of enrolled subjects was 36.8 ± 10.6 years old. The mean IOP measurements that were obtained with GAT, DCT, ORA and CST was 15.62 ± 2.33 mmHg, 17.44 ± 2.51 mmHg, 15.99 ± 3.58 mmHg and 17.24 ± 3.44 mmHg respectively. The mean CCT was 543.63 ± 36.15 μm, the mean CK was 43.35 ± 1.23 D. GAT and ORA provided IOP values not showing a statistical difference; CST and DCT IOP measurements did not show a statistical difference whereas CST provided statistically higher IOP values both than GAT and both ORA.

According to our data, CST produces IOP values that are notably higher than GAT measures; therefore they cannot be used interchangeably. If CST should be used as the next gold standard, higher IOP values will come to be considered normal.