Purpose:
To compare the test-retest reproducibility between two traditional tonometry methods, Goldmann applanation tonometry (GAT) and Schiotz tonometry (ST) with two new methods, Ocular Response Analyzer (ORA) and Dynamic Contour Tonometry (DCT).
Methods:
Consecutive Albuquerque VA Medical Center eye clinic patients that were previously diagnosed ocular hypertension, glaucoma suspect, primary open-angle or normal pressure glaucoma were recruited to participate in this prospective, observational study. For each participant, one of the authors (MSM or KDH) acquired 4 ORA, 2 GAT, 2 DCT, and 2 ST measurements in each eye, and then these measurements were repeated approximately 15-30 minutes later either by the same examiner or the other examiner. Examiners were masked to all results except the ORA signal profile and DCT quality value (which remained unmasked so the examiner could ensure good quality readings.) ORA was completed first (prior to anesthetic drops), followed by either GAT or DCT (randomized order), and then ST. To minimize tonographic effect, methods were separated by 10-15 minute intervals. Mean IOP values, including both ORA estimates of IOP (IOPg and IOPcc), were calculated for use in statistical analysis.
Results:
120 eyes were studied, with 60 eyes in the inter-examiner group and 60 eyes in the intra-examiner group (30 eyes each for MSM and KDH). Because no significant IOP reproducibility differences were evident between the two intra-examiner groups, these groups were consolidated into a single intra-examiner group for further analysis. Overall test-retest reproducibility was best for GAT and DCT, followed by ORAg, then ORAcc, and finally ST. See Table 1.
Conclusions:
IOP parameters from the ORA and DCT demonstrated good to excellent reproducibility in this study. Considering that the optimal intra-observer reproducibility for GAT-IOP has been suggested to be +/- 2.5 mm Hg, our results suggest that DCT and ORA can provide IOP estimates that are sufficiently reproducible to be usable in clinical practice.
Keywords: intraocular pressure • cornea: clinical science • anterior segment