Comparison of DCT, GAT and ORA values in patients with glaucoma

Abstract

Purpose: The Ocular Response Analyser (ORA) is a novel device for the measurement of intraocular pressure (IOP), corneal hysteresis (CH) and the corneal resistance factor (CRF). We compared the ORA with Dynamic Contour Tonometry (DCT) and Goldmann Applanation Tonometry (GAT). Methods: We examined 63 eyes of 63 glaucoma patients (primary open angle glaucoma (POAG) n=26, normal tension glaucoma (NTG) n=10, ocular hypertension (OHT) n=15, pseudoexfoliation glaucoma (PEXG) n=12). After assessment of corneal thickness (CCT) by Orbscan, IOP was measured in a randomized order with the ORA, DCT and GAT. For each device mean IOP and for the ORA mean IOP, CH and CRF were calculated and assessed for potential dependency on CCT. Results: Mean IOP in mmHg was 20.6 (±6.1 SD) for the ORA, 18.2 (±4.2 SD) for DCT and 16.5 (±4.4 SD) for GAT. Bland‐Altman‐Analysis showed a good agreement between DCT and GAT, while the ORA showed a tendency to higher values in patients with higher IOP. None of the devices showed a dependency on CCT (GAT: r²=0.12, DCT: r²=0.07, ORA: r²=0.08). There was no correlation between CH and CCT (r²=0.01), but a weak correlation between CRF and CCT (r²=0.2). Patients with NTG had a significantly (p=0.005) thinner CCT (506±55μm) than patients with POAG (567±53μm). As could be expected, OHT‐patients showed higher CCT values (592±41μm). CRF was significantly higher in the OHT (11.6±2.2) than in the POAG group (9.6±2.0) (p=0.006). For CH, we observed no difference between groups. Conclusions: The ORA showed a good agreement with DCT and GAT for “normal” IOP, but we observed higher results compared to the other methods for high IOP‐values. We observed no correlation between CCT and IOP, but a weak positive correlation between CRF and CCT.