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Goldmann tonometer error correcting prism: clinical evaluation

Authors McCafferty S, Lim G, Duncan W, Enikov ET, Schwiegerling J, Levine J, Kew C

Received 21 February 2017

Accepted for publication 16 March 2017

Published 3 May 2017 Volume 2017:11 Pages 835—840


Checked for plagiarism Yes

Review by Single anonymous peer review

Peer reviewer comments 2

Editor who approved publication: Dr Scott Fraser

Video abstract presented by Sean McCafferty.

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Sean McCafferty,1–3 Garrett Lim,2 William Duncan,2 Eniko T Enikov,4 Jim Schwiegerling,1 Jason Levine,1,3 Corin Kew3

1Department of Ophthalmology, College of Optical Science, University of Arizona, 2Intuor Technologies, 3Arizona Eye Consultants, 4Department of Aerospace and Mechanical, College of Engineering, University of Arizona, Tucson, AZ, USA

Purpose: Clinically evaluate a modified applanating surface Goldmann tonometer prism designed to substantially negate errors due to patient variability in biomechanics.
Methods: A modified Goldmann prism with a correcting applanation tonometry surface (CATS) was mathematically optimized to minimize the intraocular pressure (IOP) measurement error due to patient variability in corneal thickness, stiffness, curvature, and tear film adhesion force. A comparative clinical study of 109 eyes measured IOP with CATS and Goldmann prisms. The IOP measurement differences between the CATS and Goldmann prisms were correlated to corneal thickness, hysteresis, and curvature.
Results: The CATS tonometer prism in correcting for Goldmann central corneal thickness (CCT) error demonstrated a reduction to <±2 mmHg in 97% of a standard CCT population. This compares to only 54% with CCT error <±2 mmHg using the Goldmann prism. Equal reductions of ~50% in errors due to corneal rigidity and curvature were also demonstrated.
Conclusion: The results validate the CATS prism’s improved accuracy and expected reduced sensitivity to Goldmann errors without IOP bias as predicted by mathematical modeling. The CATS replacement for the Goldmann prism does not change Goldmann measurement technique or interpretation.

Keywords: glaucoma, tonometry, Goldmann, IOP, intraocular pressure, appalnation tonometer, corneal biomechanics, CATS tonometer, CCT, central corneal thickness, tonometer error

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