Short- and long-term reproducibility of DCT is comparable to that of GAT. GAT is more affected by CCT than DCT, measuring higher IOPs in eyes with higher central corneal thickness.
In cases with higher difference between DCT-GAT, the difference is reproducible and even present in the fellow eye. We, therefore, assume that the differences are not caused by chance, but by differing biomechanical corneal properties.
Excimer laser trabeculotomy (ELT) is a minimally invasive method for reducing intraocular pressure. It can be performed as a stand-alone procedure or in combination with cataract surgery in just a few minutes. Laser spots are applied in the anterior chamber angle via an endoscopic camera or a gonio lens. In contrast to argon laser trabeculoplasty, shunts between the anterior chamber and Schlemm's canal are prepared by a photoablative laser, thus improving the outflow of aqueous humour. Best results can be expected in patients with moderately elevated intraocular pressure and cataract undergoing the combined procedure.
Purpose: To investigate the corneal hysteresis (CH), the corneal resistance factor (CRF) and the corneal compensated intraocular pressure (IOPcc) of subjects with normal corneas and with corneal pathologies with the Ocular Response Analyzer (ORA).
Methods: IOP was measured using Goldmann applanation tonometry (GAT), dynamic contour tonometry (DCT) and ORA in 102 subjects with normal corneas and in patients with keratoconus (KC, n=32), Fuchs endothelial corneal dystrophy (FD, n=34) and penetrating keratoplasty (KP, n=50). Additionally central corneal thickness (CCT) and CH were quantified.
Results: CH and CRF were significantly reduced in all groups with corneal pathologies in comparison to the normal group (CH: 7.7 (KC), 8.9 (KP), 7.3 (FD) versus 10.3 (N), CRF: 6.4 (KC), 9.3 (KP), 8.2 (FD) versus 10.8 (N) mmHg). High significant differences were also observed in mean IOP between the control group and the groups with corneal pathologies. There was a significant correlation between CH and CCT for normal corneas and corneas with KC and KP.
Conclusions: CH and CRF are significantly decreased in patients with KC, FD and KP compared to subjects with normal corneas. Patients with corneal pathologies showed a substantial variability of mean IOP‐values evaluated by using different methods of IOP‐measurement in comparison to subjects with normal corneas suggesting that corneal properties strongly influence the validity of IOP‐measurements.
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.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.