Comparison of two analyzer measurements focusing on material stiffness among normal, treatment-naïve, and treated glaucoma eyes

Abstract

To investigate differences in biomechanical properties focusing on stiffness parameters between normal, treatment-naïve primary open-angle glaucoma (POAG), and treated POAG eyes. Retrospective case–control study, This study included 46 treatment-naïve POAG eyes, 46 POAG eyes treated with prostaglandin analogues, and 49 normal eyes used as controls; matched in terms of age and axial length. Corneal hysteresis (CH) and corneal resistance factor (CRF) were measured using an ocular response analyzer (ORA). Fifteen biomechanical parameters were measured with the Corneal Visualization Scheimpflug Technology (Corvis ST), including biomechanical glaucoma factor (BGF) and two stiffness parameters of ‘SP A1’ and ‘stress–strain index (SSI)’, which were compared among the three groups. Additionally, the area under the curve (AUC) values of the receiver-operating curve to discriminate control and treatment-naïve POAG eyes were calculated for BGF and CH. Treatment-naïve POAG eyes had higher ‘SSI’ than normal eyes even after controlling for IOP (p < 0.05, Tukey-Cramer test). Treated POAG eyes had significantly lower CRF, and higher BGF than treatment-naïve POAG eyes. There were also significant differences in CH or SP A1 among the three groups. BGF and CH had similar AUC values (0.61 and 0.59). Treatment-naïve POAG eyes had stiffer corneas compared to normal eyes, which seemed to result from the material/structure of the cornea rather than higher intraocular pressure. Antiglaucoma topical medication alters biomechanical properties measured with Corvis ST. These results are important for understanding the pathogenesis and improving the management of POAG.

Predictive Value of Dynamic Corneal Response Parameters Evaluated with Scheimpflug High-Speed Video (Corvis ST) on the Visual Field Progression in Prostaglandin Treated Ocular Hypertension and Open-Angle Glaucoma Patients

“…A higher SSI signifies a higher stiffness of the cornea. There is evidence from a cross-sectional study that treatment-naïve POAG eyes have a higher SSI when compared to control eyes [ 16 ]. There is no study in the literature to our knowledge to evaluate the role of SSI in the risk for glaucoma progression.…”

Factors affecting corneal deformation amplitude measured by Corvis ST in eyes with open-angle glaucoma

“…[ 21 ] Another recent retrospective case–control study compared treatment-naïve POAG eyes with POAG eyes treated with prostaglandin analogs (± other IOP-lowering drops) and found that the treated eyes were stiffer than untreated eyes. [ 22 ] Thus, the effect of medication on Corvis ST parameters has still not been clearly elucidated. In the present study, this aspect was not examined at all because the focus was to determine the factors affecting DA and to improve our understanding of this parameter for future long-term studies.…”

Biomechanical properties measured with dynamic Scheimpflug analyzer in central serous chorioretinopathy

“…This commercially available non-contact tonometer visualizes dynamic corneal responses to external pressure applied with an air pulse, captured by a high-speed Scheimpflug camera. Biomechanical parameters measured with Corvis ST have proven useful in managing various ocular diseases such as corneal ectasia [ 10 ] and glaucoma [ 11 ]. Given that the corneal and scleral stroma consist of similar extracellular matrix constituents, it is likely they possess common biomechanical properties [ 12 , 13 ], suggesting that corneal stiffness could serve as a surrogate marker for scleral stiffness.…”