Analysis of differences in intraocular pressure evaluation performed with contact and non-contact devices

Background: To evaluate differences of intraocular pressure (IOP) measurements performed with Goldmann applanation tonometer (GAT), dynamic contour tonometer (DCT), rebound tonometry (RT), Ocular Response Analyzer (ORA) and Corvis ST (CST) in eyes screened for refractive surgery. Methods: One eye, only the right one, of 146 patients was included in this study. Each participant was submitted to a corneal analysis with Scheimpflug camera and IOP evaluation with GAT, DCT, RT, ORA and CST. Differences in IOP values obtained thanks to each instruments were compared and then correlations between these discrepancies and morphological features such as mean keratometry (MK) and central corneal thickness (CCT) provided by Pentacam were studied. Software used to run statistical evaluations was SPSS, version 18.0. Results: Study participants had a mean age of 33.1 +/- 9.2 years old. IOP values observed in this study were 15.97 +/- 2.47 mmHg (GAT), 17.55 +/- 2.42 mmHg (DCT), 17.49 +/- 2.08 mmHg (RT), 18.51 +/- 2.59 mmHg (ORA) and 18.33 +/- 2.31 mmHg (CST). The mean CCT was 560.23 +/- 31.00 mu m, and the mean MK was 43.33 +/- 1.35 D. GAT provided significant lower values in comparison to all other devices. DCT and RT gave significantly lower intermediate IOP values than those measured with ORA and CST. All the IOP measures and the differences between devices were significantly correlated with CCT. Conclusions: According to our data, although our findings should be confirmed in further studies, GAT tonometer cannot be used interchangeably with DCT, RT, ORA and CST.