Intraocular Pressure Measurement Precision with the Goldmann Applanation, Dynamic Contour, and Ocular Response Analyzer Tonometers
Presented at: Association for Research in Vision and Ophthalmology Annual Meeting, May 2009, Fort Lauderdale, Florida.
Received 12 June 2009; received in revised form 4 August 2009; accepted 11 September 2009. published online 01 February 2010. Corrected Proof
Objective
To examine the repeatability and reproducibility of intraocular pressure (IOP) measurements obtained with the Goldmann applanation tonometer (GAT), the Pascal dynamic contour tonometer (DCT; Swiss Microtechnology AG, Port, Switzerland), and the Reichert Ocular Response Analyzer (ORA; Reichert Ophthalmic Instruments, Buffalo, NY). A secondary objective was to assess agreement between the devices.
Design
Evaluation of technology.
Participants
One hundred participants; a mixture of glaucoma suspects, patients, and control volunteers.
Methods
The IOP measurements were obtained with the GAT, DCT, and ORA by 2 of 3 experienced clinicians. Keratometry (CC) measurements were made using the IOLMaster (Carl Zeiss Meditech, AG, Jena, Germany). Three ORA corneal compensated IOP (IOPcc) measurements (in millimeters of mercury) were obtained before the instillation of anesthesia, after which 2 GAT IOP and 3 DCT IOP measurements were obtained in a randomized order. Central corneal thickness (CCT) was measured using an ultrasound pachymeter. The average ORA corneal response factor (CRF) and the average DCT ocular pulse amplitude (OPA) were determined. Intraobserver variability was calculated by the repeatability coefficient. Interobserver variability (measurement reproducibility) and device agreement were calculated with Bland-Altman analysis (mean difference [bias] and 95% limits of agreement [LoA]). The effect of corneal characteristics (CC, CCT, and CRF) on the IOP measurement differences between tonometers also was determined.
Main Outcome Measures
Repeatability and reproducibility of the GAT, DCT, and ORA IOPcc and agreement between tonometers.
Results
The repeatability coefficients for GAT, DCT, and ORA were 2.2, 2.3, and 4.3 mmHg, respectively. The intraobserver variability of ORA measurements was shown to be significantly associated with OPA and to a lesser degree with the quality of ORA waveform scans. The interobserver bias (95% LoA) was −0.8 (±3.9) mmHg for GAT IOP, −0.2 (±2.8) mmHg for DCT IOP, and −0.3 (±3.9) mmHg for ORA IOPcc. On average, GAT under-read both DCT and ORA IOP measurements by approximately 2 mmHg. The IOP measurement differences were predicted better by CRF than CCT.
Conclusions
The DCT shows excellent measurement precision, displaying the best repeatability and reproducibility of the 3 tonometers. Corneal stiffness, as defined using CRF, was associated significantly with agreement between devices. The IOP measurements with each device are not interchangeable.
Financial Disclosure(s)
Proprietary or commercial disclosure may be found after the references.
Available online:
1The National Institute for Health Research Biomedical Research Centre for Ophthalmology, Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, United Kingdom
2Department of Optometry and Visual Science, City University London, United Kingdom
3Glaucoma Research Unit, Moorfields Eye Hospital NHS Foundation Trust, London, United Kingdom
4GB Bietti Foundation for Research in Ophthalmology, Instituto Ricerca e Cura a Carattere Scientifico, Rome, Italy
Correspondence Aachal Kotecha, Glaucoma Research Unit, National Institute for Health Research Biomedical Research Centre for Ophthalmology, Institute of Ophthalmology, 11-43 Bath Street, London EC1V 9EL, United Kingdom
Manuscript no. 2009-799.
The author(s) have made the following disclosure(s): D. F. Garway-Heath - Financial Support - Reichert Inc, Zeimer Ophthalmic Systems AG. Supported in part by the Department of Health's National Institute for Health Research (NIHR) Biomedical Research Centre for Ophthalmology at Moorfields Eye Hospital NHS Foundation Trust and the UCL Institute of Ophthalmology, London, United Kingdom (AK, DFG-H). The views expressed in this publication are those of the authors and not necessarily those of the Department of Health.
The study has been supported by Pfizer with an Investigator Initiated research grant.
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