Corneal Stress Distribution Using the Procedure of Goldmann Applanation Tonometry, as Tested on a Human Cornea Model

Abstract

Objective To assess the effect of corneal thinning and changes in intraocular pressure (IOP) on the distribution of corneal stress induced by Goldmann applanation tonometry (GAT).

Methods A 2D model of a human cornea was created using a computer-aided design and finite element analysis software, employing previously reported corneal biomechanical properties. The GAT procedure was simulated, and the magnitude and distribution of stress in the corneal stroma were obtained for several corneal thicknesses, stiffnesses, and IOP.

Results A significant increase in stress was found in the outer and inner layers of the central cornea and in the inner layers of the surrounding central region. The maximal stress value was observed in the central outer layers when the stiffness was doubled, as in our theoretical baseline cornea (125.16 kPa). Minimal stress was observed in the central inner layers for a central corneal thickness of 300 µm (28.17 kPa). The thickness and stiffness of the cornea significantly influenced the magnitude of the stress, whereas the stress distribution in the cornea did not show significant changes. The change in IOP did not induce significant changes in either stress magnitude or stress distribution.

Conclusions The changes and distribution of corneal stress when a GAT procedure is performed support the idea that variations in corneal thickness and stiffness induce changes in corneal biomechanics that may be relevant for IOP readings. These findings are relevant for assessing IOP in corneas that have undergone surgical procedures or have diseases that alter their layers.

Zusammenfassung

Ziel Beurteilung der Auswirkung von Hornhautverdünnung und Veränderungen des Augeninnendrucks (IOD) auf die Verteilung der durch Goldmann Applanationstonometrie (GAT) induzierten Hornhautbelastung.

Methoden Ein 2D-Modell einer menschlichen Hornhaut wurde mithilfe einer Software für computergestütztes Design und Finite-Elemente-Analyse erstellt, wobei bereits gemessene biomechanische Eigenschaften der Hornhaut verwendet wurden. Das GAT-Verfahren wurde simuliert und das Ausmaß und die Verteilung der Spannung im Hornhautstroma für verschiedene Hornhautdicken, steifigkeiten und den Augeninnendruck ermittelt.

Ergebnisse Es wurde ein signifikanter Spannungsanstieg in den äußeren und inneren Schichten der zentralen Hornhaut sowie in den inneren Schichten der umgebenden zentralen Region festgestellt. Der maximale Spannungswert wurde in den zentralen Außenschichten beobachtet, wenn die Steifigkeit verdoppelt wurde, wie in unserer theoretischen Ausgangshornhaut (125,16 kPa). Bei einer zentralen Hornhautdicke von 300 µm (28,17 kPa) wurde eine minimale Spannung in den zentralen Innenschichten beobachtet. Die Dicke und Steifheit der Hornhaut beeinflussten das Ausmaß der Belastung maßgeblich, wohingegen die Spannungsverteilung in der Hornhaut keine signifikanten Veränderungen aufwies. Die Veränderung des Augeninnendrucks führte weder zu signifikanten Veränderungen der Belastungsgröße noch der Belastungsverteilung.

Schlussfolgerungen Die Veränderungen und die Verteilung der Hornhautbelastung bei der Durchführung eines GAT-Eingriffs stützen die Annahme, dass Variationen der Hornhautdicke und -steifheit Veränderungen in der Hornhautbiomechanik hervorrufen, die für die IOD-Messwerte relevant sein können. Diese Ergebnisse sind relevant für die Beurteilung des Augeninnendrucks bei Hornhäuten, die chirurgischen Eingriffen unterzogen wurden oder deren Schichten durch Krankenheiten verändert wurden.

Keywords

Goldmann applanation tonometry - corneal stress - glaucoma - corneal biomechanics - finite element analysis

Schlüsselwörter

Goldmann-Applanationstonometrie - Hornhautspannung - Glaukom - korneale Biomechanik - Finite-Elemente-Analyse

Publication History

Received: 22 May 2024

Accepted: 27 November 2024

Accepted Manuscript online:
27 November 2024

Article published online:
21 January 2025

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