Reproducibility, Repeatability, and Correlation of Central Corneal Thickness Measurement with the Pentacam Scheimpflug System and Ultrasound Pachymetry

Abstract

Background/Aim The importance of an accurate determination of central corneal thickness (CCT) relies on its diagnostic and therapeutic implications in glaucoma, corneal ectasias, corneal edema and endothelial function monitoring, and refractive surgery suitability, among others. We aimed to analyze the repeatability, reproducibility, correlation, and laterality variations of CCT measurements performed with the Pentacam HR and the standard of care ultrasound A-scan (USP).

Methods A cross-sectional study including CCT measurements of healthy individuals was performed by three independent examiners with the Pentacam HR and USP. Intra-observer and inter-observer variations were calculated with intra-class correlation coefficients (ICCs). Bland-Altman plots and 95% limits of agreement (95% LoA) were used to assess the agreement between devices. Linear correlation was calculated with Pearsonʼs coefficient.

Results Thirty individuals (60 eyes), including 10 (33.3%) men and 20 (66.6%) women, with a mean age of 30.0 ± 9.1 years, were studied. No statistical differences were found in CCT measurements between Pentacam HR (range 500 – 609 µm) and USP (range 498 – 628 µm). There was a high degree of correlation in repeatability and reproducibility of each independent device (ICC > 0.90). Pearsonʼs correlation between 1 vs. 2, 2 vs. 3, and 3 vs. 1 Pentacam HR attempts were 0.914, 0.958, and 0.925, respectively (p < 0.001). Corresponding results for USP were 0.957, 0.957, and 0.943 (p < 0.001). The Pentacam HR tended to overestimate CCT by a mean difference of 3.77 µm (95% LoA, − 24.9 – 18.4). Right eyes were also overestimated (− 3.6 ± 14.1 µm) with the Pentacam HR device, whereas left eyes were underestimated (1.3 ± 11.1 µm).

Conclusions The Pentacam HR device provides reliable operator-independent estimates of CCT. Right eyes exhibited a tendency to overestimate with the Pentacam HR. We suspect this difference is due to USP underestimation related to patientsʼ position while performing the study. In clinically relevant scenarios, performing a third measurement and cautiously measuring right eyes can provide higher accuracy.

Zusammenfassung

Hintergrund Die Bedeutung einer genauen Bestimmung der zentralen Hornhautdicke (CCT) ergibt sich u. a. aus ihren diagnostischen und therapeutischen Implikationen bei Glaukom, Hornhautektasie, Hornhautödem, Überwachung der Endothelfunktion und der Eignung für refraktive Chirurgie. Ziel der Studie war es, die Wiederholbarkeit, Reproduzierbarkeit, Korrelation und laterale Variationen von CCT-Messungen mittels Pentacam-HR und Standard-Ultraschall-A-Scan (USP) zu analysieren.

Methoden Es wurde eine Querschnittsstudie mit CCT-Messungen an gesunden Personen durchgeführt, die von 3 unabhängigen Untersuchern mittels Pentacam-HR und USP vorgenommen wurde. Die Abweichungen zwischen Intra-Beobachter und Inter-Beobachter wurden mit Intraklassen-Korrelationskoeffizienten (ICCs) berechnet. Bland-Altman-Plots und 95%-Übereinstimmungsgrenzen (95%-LoA) wurden verwendet, um die Übereinstimmung zwischen den Geräten zu bewerten. Die lineare Korrelation wurde mit dem Pearson-Koeffizienten berechnet.

Ergebnisse 30 Personen (60 Augen), 10 (33,3%) Männer und 20 (66,6%) Frauen mit einem Durchschnittsalter von 30,0 ± 9,1 Jahren wurden untersucht. Es wurden keine statistischen Unterschiede in den CCT-Messungen zwischen Pentacam-HR (Bereich 500 – 609 µm) und USP (Bereich 498 – 628 µm) festgestellt. Es gab einen hohen Korrelationsgrad bei der Wiederholbarkeit und Reproduzierbarkeit jedes unabhängigen Geräts (ICC > 0,90). Die Pearson-Korrelation zwischen 1 vs. 2, 2 vs. 3 und 3 vs. 1 Pentacam-HR-Versuchen war jeweils 0,914, 0,958 bzw. 0,925 (p < 0,001). Die entsprechenden Ergebnisse für USP waren 0,957, 0,957 bzw. 0,943 (p < 0,001). Die Pentacam-HR überschätzte die CCT tendenziell um eine mittlere Differenz von 3,77 µm (95%-LoA, − 24,9 – 18,4). Das rechte Auge wurde mit dem Pentacam-HR-Gerät ebenfalls überschätzt (− 3,6 ± 14,1 µm), während das linke Auge unterschätzt wurde (1,3 ± 11,1 µm).

Schlussfolgerung Das Pentacam-HR-Gerät liefert zuverlässige, bedienerunabhängige CCT-Schätzungen. Das rechte Auge zeigte eine Tendenz zur Überschätzung mit der Pentacam-HR. Wir vermuten, dass ein solcher Unterschied auf eine USP-Unterschätzung in Bezug auf die Position des Patienten während der Durchführung der Studie zurückzuführen ist. In klinisch relevanten Szenarien kann die Durchführung einer 3. Messung des rechten Auges eine höhere Genauigkeit bieten.

Key words

central corneal thickness - corneal pachymetry - Pentacam - ultrasound pachymetry

Schlüsselwörter

zentrale Hornhautdicke - Hornhautpachymetrie - Pentacam - Ultraschall-Pachymetrie

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