The range of the waveform score of the ocular response analyzer (ora) in healthy subjects.

Abstract

Purpose: The waveform score (WS) indicates the reliability of each intraocular pressure (lOP) measurement signal performed with the Ocular Response Analyzer (ORA, Reichert). We aimed to assess i) the range of waveform score in IOP measurements with ORA in healthy subjects and to ii) identify a cut-off WS value under which an ORA measurement should be discarded.

Methods: Prospective study including three ORA IOP measurements performed in the right eye of 80 healthy normal subjects. The different WS were recorded and the highest WS of the three measurements was analysed. ANOVA test was used to assess variance in repeated measurements.

Results: Mean age of 80 subjects was 46.7+/-15.6 years. Mean WS of the first IOP measurement was 4.8+/-2.0 and 4.8+/-1.7 and 5.0+/-1.9 respectively for the second and third measurements (p= 0.74). Mean WS of the analysed 240 signals (3 measurements per eye) was 4.9+/-1.9 (range: 1.2-9.5). The mean value of all the highest values per eye was 6.2+/-1.8 (range: 2.9 -9.5 and was significantly higher than the mean WS of the 240 signals together (p <0.001). The 10th percentile of all the best values was 3.7 and the 75th percentile 7.5.

Conclusion: ORA measurements with WS <3.7 should be discarded in healthy normal subjects. As much as that the corresponding quality of the waveform ORA scan is satisfying, one single measurement with a WS >7.5 could be considered as sufficient. If this score cannot be reached after three consecutive measurements, the signal with the highest WS should be selected.