Evaluation of corneal biomechanical properties using the ocular response analyzer and the dynamic Scheimpflug-Analyzer Corvis ST in high pressure and normal pressure open-angle glaucoma patients

Abstract

Purpose To characterize differences in corneal biomechanics in high (HPG) and normal pressure (NPG) primary open-angle glaucoma, and its association to disease severity. Methods Corneal biomechanical properties were measured using the Ocular Response Analyzer (ORA) and the dynamic Scheimpflug-Analyzer Corvis ST (CST). Disease severity was functionally assessed by automated perimetry (Humphrey field analyzer) and structurally with the Heidelberg Retina Tomograph. To avoid a possible falsification by intraocular pressure, central corneal thickness and age, which strongly influence ORA and CST measurements, group matching was performed. Linear mixed models and generalized estimating equations were used to consider inter-eye correlation. Results Following group matching, 60 eyes of 38 HPG and 103 eyes of 60 NPG patients were included. ORA measurement revealed a higher CRF in HPG than in NPG (P < 0.001). Additionally, the CST parameter integrated radius (P < 0.001) was significantly different between HPG and NPG. The parameter SSI (P < 0.001) representing corneal stiffness was higher in HPG than in NPG. Furthermore, regression analysis revealed associations between biomechanical parameters and indicators of disease severity. In HPG, SSI correlated to RNFL thickness. In NPG, dependencies between biomechanical readings and rim area, MD, and PSD were shown. Conclusion Significant differences in corneal biomechanical properties were detectable between HPG and NPG patients which might indicate different pathophysiological mechanisms underlying in both entities. Moreover, biomechanical parameters correlated to functional and structural indices of diseases severity. A reduced corneal deformation measured by dynamic methods was associated to advanced glaucomatous damage.

Biomechanical and Vascular Metrics Between Eyes of Patients With Asymmetric Glaucoma and Symmetric Glaucoma

“…Reviews have been published that support the role of CH as a predictor of glaucoma risk, despite the lack of a known causal link between CH and glaucoma 24,25 . Interestingly, it has been reported that there is no difference in CH between high-pressure glaucoma and low-pressure glaucoma while the group matched for IOP, CCT, and age, although there were differences in elastic parameters 26 . This may be interpreted that both high-pressure and low-pressure glaucoma have similar susceptibility to pressure fluctuations while chronic exposure to higher pressure leads to modifications of the tissue structure leading to stiffening.…”

In Vivo Evaluation of Corneal Biomechanics Following Cross-Linking Surgeries Using Optical Coherence Elastography in a Rabbit Model of Keratoconus

“…Existing clinical devices include the ocular response analyzer and the Corvis-ST, both of which can only analyze corneal biomechanics qualitatively. 46 – 48 The OCE technique has been used for nondestructive, noncontact quantitative evaluation of the elastic modulus of corneal tissue and is considered to be the elastography technique with the greatest potential for clinical translation. 45 , 49 , 50 Conventional ARF OCE systems typically use ultrasonic transducers with centimeter-scale geometries and focused excitation to meet the requirements for optical detection.…”