Factors influencing intermethod agreement between goldmann applanation, pascal dynamic contour, and ocular response...

Area of Science:

• Ophthalmology
• Biomedical Engineering
• Optometry

Background:

• Accurate intraocular pressure (IOP) measurement is crucial for diagnosing and managing glaucoma.
• Goldmann applanation tonometry (GAT) is a widely used method, but its accuracy can be affected by corneal properties.
• Newer tonometers like the Ocular Response Analyzer (ORA) and Pascal Dynamic Contour Tonometer (DCT) offer alternative methods for IOP assessment, incorporating corneal biomechanical properties.

Purpose of the Study:

• To investigate the factors influencing measurement agreement among GAT, ORA, and DCT for intraocular pressure (IOP).
• To identify specific corneal parameters that affect the concordance of IOP readings obtained from different tonometry devices.
• To evaluate the interchangeability of IOP measurements from these three common tonometry methods.

Main Methods:

• The study included 243 eyes of subjects diagnosed with primary open-angle glaucoma, ocular hypertension, glaucoma suspect, or normal tension glaucoma.
• Measurements included corneal hysteresis (CH), corneal resistance factor (CRF), ocular pulse amplitude, and IOP using ORA (IOPcc, IOPg), DCT, and GAT.
• Corneal curvature, thickness, axial length, retinal nerve fiber layer thickness, visual field data, diabetes status, and topical IOP-lowering treatment were also recorded.
• Statistical analyses included ANOVA, Bland-Altman, and regression analyses to assess IOP agreement and influencing factors.

Main Results:

• Mean DCT-IOP and ORA-IOPcc were significantly higher than ORA-IOPg and GAT-IOP.
• Multivariate regression models indicated that variations in CH, CRF, and IOP level almost completely explained intermethod differences between ORA (IOPg, IOPcc) and DCT (r(2)=0.98 to 0.99).
• In contrast, intermethod variability between GAT-IOP and the other three IOP metrics was only partially explained by the evaluated factors (r(2)=0.31 to 0.65).

Conclusions:

• The four IOP measurement variables (ORA-IOPcc, ORA-IOPg, DCT-IOP, GAT-IOP) are not interchangeable.
• Corneal hysteresis (CH) and corneal resistance factor (CRF), as measured by ORA, were the most significant confounders affecting IOP measurement agreement.
• Incorporating CH and CRF measurements may improve the accuracy of transcorneal IOP estimations.