Hysteresis Measurement as a New Tool to Access Biomechanical Properties of the Cornea

Abstract

Abstract: : Purpose: To compare corneal hysteresis measurements in eyes with normal corneas, Fuchs’ dystrophy and corneal grafts. Methods: The Ocular Response Analyzer (ORA; Reichert Instruments ^TM) provides instantaneous corneal applanation by an air puff, and an electro–optical collimation system detects both the inward and outward movements directly related to the cornea. In this manner, corneal hysteresis, a component of the material and viscoelastic properties of the cornea, can be determined. A total of 52 eyes of 26 subjects were analyzed prospectively, including 14 eyes with Fuchs’ dystrophy, 8 eyes with penetrating keratoplasty, and 30 normal eyes. All eyes underwent corneal hysteresis measurements using the ORA. The mean of two sequential measurements for each eye was used for analysis. Results: The mean measurement was 11.385 + 1.750 for normal corneas, 8.102 +1.856 for eyes with Fuchs’ dystrophy and 8.778 +1.156 for eyes with corneal grafts. The differences in the measurements between normal corneas and those with Fuchs’ dystrophy (3.166; 95% CI: 1.943 to 4.390; P<0.001) as well as with penetrating keratoplasty (2.812; 95% CI: 1.453 to 4.172; P<0.001) were statistically significant. The differences in the measurements between corneas with Fuchs’ dystrophy and penetrating keratoplasty were not statistically significant (P=0.54). Conclusions: Normal corneas have higher hysteresis measurements than corneas in patients with Fuchs’ dystrophy and penetrating keratoplasty. Hysteresis measurements, which assess biomechanical properties of the cornea, may be used as a tool to distinguish between normal and disturbed corneas.

Keywords: intraocular pressure • cornea: clinical science • clinical (human) or epidemiologic studies: systems/equipment/techniques