A Comparison of the Corrected Intraocular Pressure Obtained by the Corvis ST and Reichert 7CR Tonometers in Glaucoma Patients

Abstract

The purpose of the study was to investigate the accuracy of two corrected intraocular pressure (IOP) measurements by Corvis Scheimpflug Technology (CST)-IOPpachy and by corneal-compensated IOP (IOPcc) using the Reichert 7CR (7CR) tonometers. We also investigated the effects of corneal anatomical and structural parameters on the IOP measurements. The participants included 90 primary open-angle glaucoma patients. We assessed the IOP measurements, obtained by the CST, 7CR, and Goldmann applanation tonometer (GAT), using a paired t-test with Bonferroni correction, Bland-Altman plots, and multiple regression analyses. The 7CR-IOPcc gave the highest value (15.5 ± 2.7 mmHg), followed by the 7CR-IOPg (13.7 ± 3.1 mmHg), GAT-IOP (13.6 ± 2.2 mmHg), CST-IOP (10.3 ± 2.6 mmHg), and CST-IOPpachy (9.7 ± 2.5 mmHg). The values of CST-IOPpachy were significantly lower than those obtained by the other IOP measurement methods (all, p < 0.01). The values of 7CR-IOPcc were significantly higher than those obtained by the other IOP measurement methods (all, p < 0.01). Bland-Altman plots showed a mean difference between the GAT-IOP and the other IOP measurements (CST-IOP, CST-IOPpachy, 7CR-IOPg, and 7CR-IOPcc), which were −3.20, −3.82, 0.14, and 2.00 mmHg, respectively. The widths of the 95% limits of agreement between all pairs of IOP measurements were greater than 3 mmHg. With the exception of the 7CR-IOPcc, all of the IOP variations were explained by regression coefficients involving gender, average corneal curvature, and central corneal thickness. The IOP values obtained by the GAT, CST, and 7CR were not interchangeable. Each new IOP measurement device that was corrected for ocular structure had its own limitations.

Age-Related Variations of Rabbit Corneal Geometrical and Clinical Biomechanical Parameters

“…Ref. [ 7 ] reports that a reduced applanation (optical reflectance) signal width and/or amplitude perhaps indicate increased localized deformation, which would cause the optical detector to see a smaller reflectance area, similar to the corneal surface after LASIK [ 7 ]. ORA waveform of keratoconus patient showed a similar characteristic [ 11 , 12 ].…”

“…ORA applies similar principle and reports two corneal biomechanical parameters termed Corneal Hysteresis (CH) and Corneal Resistance Factor (CRF) ( Figure 1 ). These two devices have their own advantages and limitations [ 7 ], and in this study, corneal biomechanical parameters in vivo are obtained based on ORA.…”

A Comparative Study Between the Goldmann Applanation Tonometer and the Non-Contact Air-Puff Tonometer (Huvitz HNT 7000) in Normal Eyes

“…Reliable results relative to GAT results for Goldmann-correlated intraocular pressure (IOPg) were obtained with the Reichert PT-100 (p=0.64) 7 and Reichert CR7 (p=0.52) even in patients with all pressure levels, although lower accuracy was achieved when considering the corneal-compensated IOP (IOPcc) modality in Reichert CR7 (p<0.01) ( Table 4 ). 18 …”

Evaluation of biomechanically corrected intraocular pressure using Corvis ST and comparison of the Corvis ST, noncontact tonometer, and Goldmann applanation tonometer in patients with glaucoma

“…The Goldmann applanation tonometer (GAT) is presently the gold standard for clinical IOP measurements, and the traditional noncontact tonometer (NCT) is widely used in optometric practice as it is rapid and simple to operate with respect to measurement of IOP. Nevertheless, IOP readings increased as the CCT increased [2][3][4][5][6][7][8][9][10][11][12], axial length decreased [13,14], age increased [9,12], and the corneal curvature decreased [8,15] when the two tonometers are used.…”

“…Previously, we compared the IOPpachy-Corvis and the IOP obtained with GAT; it is named as IOP-GAT, and found that the two measurements were not interchangeable. This may be because IOPpachy-Corvis was not sufficiently unaffected by the ocular biomechanical parameters [11]. However, in 2016, Corvis ST developed a new parameter called biomechanically corrected IOP (bIOP-Corvis).…”