Reproducibility of viscoelastic property and intraocular pressure measurements obtained with the Ocular Response Analyzer

Abstract

. Purpose: To analyse the reproducibility of corneal hysteresis (CH), corneal resistance factor (CRF), Goldmann‐correlated intraocular pressure (IOPg) and corneal‐compensated intraocular pressure (IOPcc) obtained with the ocular response analyzer (ORA). Methods: This is a prospective study, nonmasked, of eight successive examinations with the ORA device in 60 normal eyes. Using 30 eyes (one eye per subject), the reproducibility was assessed by comparing the first series of four examinations to the second four and by calculating the within‐subject coefficient of variation. The correlation and difference with the fellow eye were analysed, respectively. Results: The mean values were 10.7 ± 1.8 mmHg, CRF; 10.6 ± 1.6 mmHg, CH; 15.9 ± 3.9 mmHg, IOPg and 16.2 ± 3.7 mmHg, IOPcc. The reproducibility was significantly different for CRF (5.2 ± 5.9%), CH (7.3 ± 8.6%), IOPg (7.7 ± 6.7%) and IOPcc (10.1 ± 8.0%); p < 0.001. Considering the reproducibility, CRF correlated with CH (rs = 0.55; p < 0.001) and showed to be independent of IOPg and IOPcc. The score spread was best for CRF (2.6 ± 1.5 mmHg; 24.0%) compared to IOPg (4.3 ± 1.5 mmHg; 28.1%) and CH (3.1 ± 1.7 mmHg; 29.9%) and worst for IOPcc (5.5 ± 2.5 mmHg; 34.4%). The lowest difference with the fellow eye was observed for CRF (5.0%; p = 0.09). The correlation with the fellow eye was high, especially for IOPcc and CRF (rs > 0.9; p < 0.001) followed by IOPg and CH (rs > 0.8; p < 0.001). Conclusion: The ORA device provides reproducible information on viscoelastic properties of the cornea in normal eyes notably CRF and CH. IOPcc was less reproducible. Four measurements per eye were necessary to reach a 10% precision and six for 5%.

Corneal biomechanical properties measured with the Ocular Response Analyser in a myopic population

“…For three measurements on each eye Kopito et al. 17 found a relative difference between the two eyes of magnitude about 9.4 ± 10.1% and 7.5 ± 7.7% in CH and CRF respectively, or roughly 1.0 ± 1.1mmHg and 0.8 ± 0.8 mmHg; unfortunately they did not give summary statistics for the signed differences. If we assume that the inter‐ocular differences in CH and CRF were normally distributed about zero, these values correspond to standard deviations in CH and CRF of about 1.5 and 1.3 mmHg respectively, similar to those found in the present study.…”

“…The only other previous study is that of Kopito et al. 17 who found in 30 normal adult subjects that the means of three right and left eye measurements were well correlated, the mean magnitudes of the differences between the eyes being 9.4 ± 10.1% and 7.5 ± 7.7% in CH and CRF respectively.…”

Tonographic Effect of Ocular Response Analyzer in Comparison to Goldmann Applanation Tonometry

“…The ORA-measurements have shown to be reproducible in several studies [17, 18, 23]. There are only few studies evaluating an influence of repeated ORA measurements or ocular massage on the IOP in healthy subjects [17, 24, 25].…”

Repeatability of corneal biomechanical measurements in children wearing spectacles and orthokeratology lenses

“…Hence, the repeatability of CH and CRF measurements in children is an important issue. Whilst some papers have reported the repeatability and reproducibility of the ORA, all reports are on adults only 11–16 . However, as the ORA is a non‐contact tonometer which will eject air pulse during measurements, repeatability of measurements may be different in children compared to adults.…”