Clinical evaluation of multiparameter correction equations for Goldmann applanation tonometry

Abstract

Purpose To evaluate and compare the multiparameter equations in correcting intraocular pressure (IOP) measurements obtained using the Goldmann applanation tonometer (IOPG) for the effects of central corneal thickness (CCT), corneal curvature (R), and age in different ethnic populations. Methods Data of IOPG, CCT, R, and age were collected from three clinical centers. The sample size consisted of 945 eyes of 945 glaucoma patients or suspects (669 Europeans, 127 African Americans, and 149 Indians). The 'corrected IOP' was calculated using five multiparameter equations to decrease the association of CCT, R, and age with measured IOP. Regression analyses were performed to calculate variance (r 2 ) and determine the association of CCT, R, and age with IOPG and corrected IOP (residual association). Results Overall, CCT accounted for the majority of variance in IOPG, while R and age had a much smaller effect, with the combined effect on IOPG ranging from 4.7 to 7.5% in the three data sets. The residual association of CCT, R, and age with corrected IOP in the three groups ranged from 0.2 to 1.3% and 0.5 to 1.8% with the application of the Elsheikh and the Chihara equations, respectively. The residual association of CCT, R, and age with corrected IOP calculated using the Ehlers, Orssengo and Pye, and Shimmoyo equations were 7-11.5, 1.8-11.7, and 4.6-8.3%, respectively. Conclusion The Elsheikh and the Chihara equations better decreased the association of CCT, R, and age with measured IOP than the Ehlers, Orssengo and Pye, and Shimmoyo equations.

A Comparative Analysis of Goldmann Tonometry Correction

“…IOP measured with different methods, a multivariate analysis was conducted 9 . The findings presented in Table 3 (Table 3).…”

“…11 The effect of other parameters that influence GAT have been investigated more recently (age, axial length and biomechanical parameters). 8,9,12,13 Nevertheless, none of these attempts have yielded a universally accepted correction formula. 7,9,13 The consequence of this is that there are several correction methods available rendering it difficult to make a comparative analysis between different studies.…”

“…The corrective function is referred to as the true intraocular pressure (IOPc) function. [4][5][6][7][8][9] Earlier proposals for correction only accounted for the thickness of the cornea; 10 subsequent methods also included the radius of the curvature. 11 The effect of other parameters that influence GAT have been investigated more recently (age, axial length and biomechanical parameters).…”

Influence of Pachymetry and Intraocular Pressure on Dynamic Corneal Response Parameters in Healthy Patients

“…37 It was developed using numerical, finite element simulations of the Corvis ST procedure applied on human eye models with different tomographies (including thickness profiles), ages, and IOP values. 8,35,[38][39][40] The analysis was used to provide bIOP, which are IOP estimates significantly less affected by corneal parameters and given as a function of measured IOP, CCT, and age. The bIOP formula used was a modified algorithm of the published formula 37 :…”

Clinical Evaluation of Methods to Correct Intraocular Pressure Measurements by the Goldmann Applanation Tonometer, Ocular Response Analyzer, and Corvis ST Tonometer for the Effects of Corneal Stiffness Parameters

“…6,13 In response, a number of multiparameter correction equations 10 were developed to mitigate errors induced by CCT, central corneal radius of curvature (R), and age on GAT-IOP, and these equations were successful to different extents in reducing the association of IOP measurements with the cornea's stiffness parameters. [14][15][16] As a further response to the problems reported in GAT with the stiffness-related inaccuracies, the dynamic contour tonometer (DCT) was developed by SMT Swiss Microtechnology AG, Switzerland, on the basis of the principle of contour matching (Fig. 1A).…”