Repeatability of Intraocular Pressure and Corneal Biomechanical Properties Measurements by the Ocular Response Analyser

Zusammenfassung

Hintergrund: Der Ocular Response Analyser (ORA, Reichert Ophthalmic Instruments) ist ein Non-Contact-Applanationstonometer, welches die Messung des Intraokulardrucks (IOD) als Goldmann-äquivalenten IODg und als korneal kompensierten IODcc (IOD-Wert unabhängig von kornealen Eigenschaften) erlaubt. Zusätzlich können korneale biomechanische Eigenschaften in Form der kornealen Hysterese (CH) und des kornealen Resistenzfaktors (CRF) bestimmt werden. Ziel dieser Studie war es, die Reproduzierbarkeit dieser Messwerte zu prüfen. Patienten und Methoden: Bei 49 gesunden Probanden wurde ein Auge für die Untersuchungen randomisiert ausgewählt und die Messungen mit dem ORA viermal konsekutiv vor der Goldmann-Applanationstonometrie (GAT) durchgeführt. Als Masse der Wiederholbarkeit wurden der Wiederholbarkeitskoeffizient (RC), der Variationskoeffizient (CV) und der Intraclass-Korrelationskoeffizient (ICC) für die in jeder Messreihe erhobenen Messwerte berechnet. Ergebnisse: Die CH war die variabelste und der IOPg die wiederholbarste Messung, mit einem RC von jeweils 2,61 und 1,97 und einem ICC von 0,86 und 0,92 entsprechend. CV schwankte zwischen 5,73 % für IOPg und 12,38 % für CH. ORA IOP-Messungen waren höher als GAT (IOPcc = 17,43 ± 3,23; IOPg 17,53 ± 3,0; GAT 15,75 ± 2,77 mmHg). Schlussfolgerungen: ORA-Messungen zeigen eine gute Kurzzeit-Wiederholbarkeit bei gesunden Probanden. Das Gerät scheint damit in der klinischen Routine einsetzbar zu sein.

Abstract

Background: The Ocular Response Analyser (ORA, Reichert Ophthalmic Instruments) is a non-contact applanation tonometer, providing two measures of intraocular pressure (IOP) - IOPg which represents a Goldmann equivalent IOP measure and IOPcc, representing a measure of IOP independent of corneal effects. In addition, the device provides two measures believed to represent corneal biomechanical properties: corneal hysteresis (CH) and corneal resistance factor (CRF). The aim of this study was to assess the repeatability of these measurements. Patients and Methods: One randomly chosen eye from 49 healthy volunteers was measured four times consecutively with the ORA prior to Goldmann applanation tonometry (GAT). The repeatability coefficient (RC), the coefficient of variation (CV) and the intraclass correlation coefficient (ICC) were calculated as a measure of intrasession repeatability. Results: CH was the most variable and IOPg the most repeatable measure, with an RC of 2.61 and 1.97, respectively, and ICC of 0.86 and 0.92, respectively. CV ranged between 5.73 % for IOPg and 12.38 % for CH. ORA IOP measurements were higher than GAT (IOPcc = 17.43 ± 3.23; IOPg = 17.53 ± 3.0; GAT = 15.75 ± 2.77 mmHg). Conclusions: ORA measurements show good short-term repeatability in normal volunteers. Thus, this device appears to be applicable in clinical practice.

Schlüsselwörter

Ocular Response Analyser - korneale Hysterese - kornealer Resistenzfaktor - korneal kompensierter IOP

Key words

ocular response analyzer - corneal hysteresis - corneal resistance factor - corneal compensated IOP

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