Aims To compare the biomechanically corrected intraocular pressure (IOP) estimate (bIOP) provided by the Corvis-ST with Goldmann applanation tonometry (GAT-IOP) in patients with high-tension and normal-tension primary open-angle glaucoma (POAG; HTG and NTG), ocular hypertension (OHT) and controls. Moreover, we compared dynamic corneal response parameters (DCRs) of the Corvis-ST in POAG, OHT and controls, evaluated the correlation between global visual field parameters mean deviation and pattern SD (MD and PSD) and DCRs in the POAG group.
Methods 156 eyes of 156 patients were included in this prospective, single-centre, observational study, namely 41 HTG and 33 NTG, 45 OHT cases and 37 controls. Central corneal thickness (CCT), GAT-IOP and bIOP were measured, GAT-IOP was also adjusted for CCT (GATAdj). DCRs provided by Corvis-ST were evaluated, MD and PSD were recorded by 24–2 full-threshold visual field. To evaluate the difference in DCRs between OHT, HTG and NTG, a general linear model was used with sex, medications and group as fixed factors and bIOP and age as covariates.
Results There was a significant difference between GAT-IOP, GATAdj and bIOP in NTG and HTG, OHT and controls. NTG corneas were significantly softer and more deformable compared with controls, OHT and HTG as demonstrated by significantly lower values of stiffness parameters A1 and highest concavity and higher values of inverse concave radius (all p<0.05). There was a significant correlation (p<0.05) between MD, PSD and many DCRs with POAG patients with softer or more compliant corneas more likely to show visual field defects.
Conclusions Corneal biomechanics might be a significant confounding factor for IOP measurement that should be considered in clinical decision-making. The abnormality of corneal biomechanics in NTG and the significant correlation with visual field parameters might suggest a new risk factor for the development or progression of NTG.
- optic nerve
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Contributors RV initiated the project, designed data collection tools, monitored data collection for the whole trial, wrote the statistical analysis plan, cleaned and analysed the data, drafted and revised the paper. SR and NV collected and analysed the data as well as drafted and revised the paper. GC wrote the statistical analysis plan and revised the draft and approved the final version of the paper. AE, CEW, MB, AC and RC contributed substantially in conception and design of the study revised and approved the draft and the final version of the paper.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Disclaimer OCULUS Optikgeräte GmbH did not take part in design, analysis or interpretation of the results.
Competing interests RV and AE are consultants for OCULUS Optikgeräte GmbH.
Patient consent for publication Not required.
Ethics approval The study data were acquired under ethical approval of the Royal Liverpool University Hospital for service development audit purposes and adhered to the tenets of the Declaration of Helsinki.
Provenance and peer review Not commissioned; externally peer reviewed.
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