Intra-Ocular Pressure Measurement in a Patient with a Thin, Thick or Abnormal Cornea



Colin I. Clement1, 2, 3, 4, Douglas G.A. Parker1, 4, Ivan Goldberg*, 1, 2, 3
1 Eye Associates, 4/187 Macquarie Street Sydney NSW 2000, Australia
2 Glaucoma Unit, Sydney Eye Hospital, Australia
3 Discipline of Ophthalmology, The University of Sydney, Australia
4 Gosford and Wyong Eye Surgery, Australia


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© Clement et al.; Licensee Bentham Open.

open-access license: This is an open access article licensed under the terms of the Creative Commons Attribution-Non-Commercial 4.0 International Public License (CC BY-NC 4.0) (https://creativecommons.org/licenses/by-nc/4.0/legalcode), which permits unrestricted, non-commercial use, distribution and reproduction in any medium, provided the work is properly cited.

* Address correspondence to this author at the Eye Associates, 4/187 Macquarie Street Sydney NSW 2000. Australia; E-mail: eyegoldberg@gmail.com


Abstract

Accurate measurement of intra-ocular pressure is a fundamental component of the ocular examination. The most common method of measuring IOP is by Goldmann applanation tonometry, the accuracy of which is influenced by the thickness and biomechanical properties of the cornea. Algorithms devised to correct for corneal thickness to estimate IOP oversimplify the effects of corneal biomechanics. The viscous and elastic properties of the cornea influence IOP measurements in unpredictable ways, a finding borne out in studies of patients with inherently abnormal and surgically altered corneal biomechanics. Dynamic contour tonometry, rebound tonometry and the ocular response analyzer provide useful alternatives to GAT in patients with abnormal corneas, such as those who have undergone laser vision correction or keratoplasty. This article reviews the various methods of intra-ocular pressure measurement available to the clinician and the ways in which their utility is influenced by variations in corneal thickness and biomechanics.

Keywords: Applanation, corneal pathology, corneal thickness, hysteresis, intraocular pressure.