Corneal and Epithelial Thickness Measurements: Comparability between two Different Ocular Coherence Tomography Devices

Abstract

Background Corneal and epithelial thickness maps obtained with high-frequency ultrasound were first used to diagnose keratoconus. Anterior segment OCT has recently become widely used in many conditions especially in preoperative planning before refractive surgery, keratoconus diagnosis, keratoconus progression monitoring, hydrops formation, and epithelial healing monitoring. We compare epithelial and pachymetric thickness-based parameters from two different Fourier-domain optical coherence tomography (OCT) devices as to whether they can be used interchangeably.

Methods Retrospective, comparative chart review. This study comprises 24 normal consecutive eyes and 32 consecutive post-SMILE eyes with corneal thickness and epithelial thickness maps obtained using two different OCT devices (Cirrus 5000, Carl Zeiss Meditec, Germany and Avanti RTVue 100, OptoVue Inc., USA). The following common parameters in the print-out of the two OCT devices were examined: minimum corneal thickness (Pachy min), minimum corneal thickness minus median corneal thickness (Pachy min−med), average corneal thickness of the superonasal octant minus the average corneal thickness of the inferotemporal octant (Pachy SN−IT), average corneal thickness of the superior octant minus average corneal thickness of the inferior octant (Pachy S−I), minimum epithelial thickness (Epi min), and maximum epithelial thickness (Epi max).

Results Pachy min and Epi max measurements matched well between the two devices (ICC at 0.906 and 0.839, respectively). We found a significant correlation in Pachy min (p = 0.040), Pachy min−med (p = 0.033), and Epi max (p < 0.001) in the normal eye group. Only Pachy min and Epi max measurements (p < 0.001 for both) exhibited a significant correlation between the two devices in the post-SMILE group.

Conclusion Anterior segment OCT is a valuable method for evaluating quantitative corneal and epithelial thickness measurements. However, measurements may differ between devices, and they should not be used interchangeably.

Zusammenfassung

Hintergrund Zunächst wurden Hornhaut- und Epitheldickenkarten mit hochfrequentem Ultraschall hergestellt und zur Diagnose von Keratokonus verwendet. Seit einiger Zeit wird die optische Kohärenztomografie (OCT) des vorderen Augenabschnitts bei vielen Erkrankungen eingesetzt, insbesondere bei der präoperativen Planung vor refraktiven Eingriffen, der Diagnose von Keratokonus, der Verlaufskontrolle bei progressivem Keratokonus sowie der Überwachung der Epithelheilung. Wir haben die epithelialen und pachymetrischen Dickenparameter von 2 verschiedenen optischen Kohärenztomografen verglichen, um zu prüfen, ob die Geräte austauschbar verwendet werden können.

Methoden Retrospektive, vergleichende Datenanalyse. Diese Studie umfasst 24 normale und 32 post-SMILE-Augen, deren Hornhautdicken- und Epitheldickenkarten mit 2 verschiedenen OCT-Geräten (Cirrus 5000, Carl Zeiss Meditec, Deutschland und Avanti RTVue 100, OptoVue Inc., USA) erstellt wurden. Es wurden die gemeinsamen Parameter der beiden OCT-Geräte untersucht: minimale Hornhautdicke (Pachy min), minimale Hornhautdicke minus mediane Hornhautdicke (Pachy min−med), durchschnittliche Hornhautdicke des superonasalen Oktanten abzüglich der durchschnittlichen Hornhautdicke des inferotemporalen Oktanten (Pachy SN−IT), durchschnittliche Hornhautdicke des oberen Oktanten minus durchschnittliche Hornhautdicke des unteren Oktanten (Pachy S−I), minimale Epitheldicke (Epi min) und maximale Epitheldicke (Epi max).

Ergebnisse Die Messungen von Pachy min und Epi max stimmten gut zwischen den beiden Geräten überein (ICC betrug 0,906 bzw. 0,839). In der Gruppe der normalen Augen gab es eine signifikante Korrelation zwischen Pachy min (p = 0,040), Pachy min−med (p = 0,033) und Epi max (p < 0,001). In der post-SMILE-Gruppe zeigten nur die Messungen von Pachy min und Epi max (p < 0,001 für beide) eine signifikante Korrelation zwischen den beiden Geräten.

Schlussfolgerung Das OCT des vorderen Augenabschnitts ist eine wertvolle Methode zur Auswertung der quantitativen Hornhaut- und Epitheldickenmessungen. Die Messungen können jedoch von Gerät zu Gerät unterschiedlich sein und sollten nicht austauschbar verwendet werden.

Conclusion Box

Already known:

• Corneal and epithelial thickness-based parameters can be used in diagnosing different corneal conditions.

• Anterior segment OCT devices provide reliable and reproducible measurements of corneal and epithelial thicknesses.

Newly described:

• Corneal and epithelial thickness measurements obtained with Avanti and Cirrus OCT devices cannot be used interchangeably.

• Cut-off values for the corneal and epithelial thickness-based parameters should be established specifically to each OCT device.

Keywords

cornea - Fourier-domain OCT - epithelial thickness - corneal thickness - comparison of device

Schlüsselwörter

Kornea - Fourier-Domain-OCT - Epitheldicke - Hornhautdicke - Gerätevergleich

Publikationsverlauf

Eingereicht: 06. März 2024

Angenommen: 11. März 2025

Artikel online veröffentlicht:
28. Mai 2025

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