Reproducibility of intraocular pressure and outflow facility measured by pneumatic tonography and Schiotz tonography

The purpose of this study was to compare means, variability, and reproducibility in intraocular pressure and in outflow facility measured repeatedly over several days by Bio-Rad pneumatonography and Schiotz tonography in normal human volunteers. For each instrument a measurement of intraocular pressure and one of outflow facility were obtained at each of three repeated examinations of eight healthy subjects in the supine position. For pressure, the Bio-Rad mean was significantly higher by 5.31 mmHg than the Schiotz mean (p < 0.00005). Reproducibility was 71.1% and 59.0% for the Bio-Rad and Schiotz, respectively. For outflow, the Bio-Rad and Schiotz means were not significantly different. Reproducibility was 17.3% and 58.7% for the Bio-Rad and Schiotz, respectively. For measuring pressure, both the Bio-Rad and Schiotz instruments had good reproducibility; for measuring outflow, the Bio-Rad and Schiotz instruments had low and good reproducibility, respectively.