Comparison of IOP measurement by ocular response analyzer, dynamic contour, Goldmann applanation, and noncontact tonometry

PURPOSE. To assess the agreement among ocular response analyzer (ORA), dynamic contour tonometry (DCT), Goldmann applanation tonometry (GAT), and noncontact tonometry (NCT), and to determine the effects of central corneal thickness (CCT) and corneal hysteresis (CH) on intraocular pressure (IOP) measurements with these devices. METHODS. Sixty healthy volunteers were recruited. The average of ORA (corneal compensated IOP [IOP-ORAcc] and Goldmann-correlated IOP [IOP-ORAg]), DCT GAT and NCT levels were compared and the devices were examined with respect to CCT and CH. One-way analysis of variance and Pearson correlation tests were used for statistical analysis. RESULTS. Mean CCT was 543.28 +/- 36.2 mu m and mean CH was 10.87 +/- 1.27 mmHg. Mean IOP obtained using DCT was 16.4 +/- 2.9 mmHg, whereas those provided by ORA were 15.8 +/- 2.9 mmHg for IOP-ORAcc and 15.1 +/- 2.8 mmHg for IOP-ORAg. The mean IOPs obtained using GAT and NCT were 14.8 +/- 3.1 mmHg and 14.7 +/- 2.8 mmHg. The differences between the measurements of DCT and GAT, NCT and IOP-ORAg were statistically significant (p=0.002, p=0.002, and p=0.015, respectively), but not between DCT and IOP-ORAcc (p=0.263). We did not detect a significant correlation between DCT and CCT and IOP-ORAcc and CCT (p=0.081 and p=0.093). No correlation was observed between IOP-ORAg and CCT (p=0.067). We found a significant correlation between GAT and CCT and NCT and CCT (p=0.004 and p=0.001). CH was detected to be correlated only to IOP-ORAcc (p=0.017). CONCLUSIONS. IOP readings detected by DCT and IOP-ORAcc were not found to be clinically interchangeable with GAT and NCT readings. IOP-ORAcc and DCT readings may be regarded as comparable and independent of CCT in the range of the normal IOP. (Eur J Ophthalmol 2009; 19: 936-41)