High Reliability in Patients with Normal Intraocular Pressure Using the G3 Ocular Response Analyzer

Abstract

Purpose : Intraocular pressure (IOP) measurement is a crucial clinical maneuver of ophthalmological examination. The increase in IOP is the main risk factor for glaucoma to both develop and progress. Remembering that glaucoma, it is the first cause of irreversible blindness in the world. The ocular response analyzer (ORA) is a method to assess IOP and some biomechanical properties of the cornea. The reliability of this method has been demonstrated in the newest version of ORA (generation 3 or G3) in ocular hypertension (OH) eyes, finding an excellent reliability results in all its parameters (ARVO 2022). The main objective of this study is to investigate the reliability ORA G3 in eyes with normal intraocular pressure.

Methods : This cross-sectional study to assess the reliability of IOP included 18 non-consecutive patients with no glaucoma or OH and IOPs at the moment of the study less than 21 mm Hg. Three consecutive measurements were made with an interval of 1 to 2 minutes between each measurement to restart the equipment, all of them by the same operator. In all subjects, central corneal thickness (CCT) was measured with the Cirrus 6000 optical coherence tomography (OCT). The statistical package SPSS version 25 was used to analyze the intraobserver reliability with the intraclass correlation coefficient (ICC) test, as well as the Pearson test to evaluate the correlation of the variation with the central corneal thickness (CCT).

Results : Thirty-six eyes of 18 patients were analyzed (10 female, 8 male). The mean age was 29.7 ± 3.8 years. In regards of the reliability analysis an excellent intraclass correlation coefficient was demonstrated in corneal compensated IOP (IOPcc), corneal hysteresis (CH) and Goldmann correlated IOP (IOPg) (r = 0.87 p = 0.000, r = 0.89 p = 0.000, r = 0.91 p = 0.000 respectively). The Waveform score (WS) had an acceptable ICC (r = 0.55 p = 0.002).
The mean CCT was 529 ± 32.1 µm and there was a very weak, non-significant correlation between CCT and the level of variation of IOPcc (r = 0.3, p = 0.05) or in with IOPg (r = 0.2 p = 0.13).

Conclusions : This study demonstrates that performing IOP measurements using ORA G3 in patients with normal intraocular pressure has excellent reliability, as it was previously demonstrated in patients with OH, making it a very good method for assessing IOP.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.