The Relationship between Corneal Biomechanics and Corneal Shape in Normal Myopic Eyes

Introduction In a broad review, evidence that the corneal biomechanical properties influence the results and outcomes of various ocular measurements and procedures has existed for some time [1,2]. However, assessing the biomechanical properties of corneal tissue in vivo has previously not been possible. With the recent introduction of the Reichert Ocular Response Analyzer (ORA), direct clinical measurements of the corneal biomechanical response are now available and provide novel ways for the preoperative screening of refractive surgery candidates. The ORA uses a high-speed air puff to deform the cornea and records two corneal biomechanical metrics termed corneal hysteresis (CH) and corneal resistance factor (CRF). CH may predominantly reflect the viscous properties [3], whereas CRF is thought to reflect overall viscoelastic resistance of the cornea [4]. The ORA has been widely used to study corneal biomechanical properties [5-7], and it has been suggested that different clinical conditions would affect corneal biomechanical properties, such as the decrease in CH with keratoconus and corneal surgeries [8]. Meanwhile, more recently published studies have set out to discover the exact clinical features and value of CH and CRF as corneal biomechanical metrics [9,10]. Recently, it has been reported that CRF strongly correlates with corneal spherical-like aberrations, especially in severe keratoconus, which implies it should be considered an additional factor in keratoconus grading [11]. Additionally, it is well known that keratoconus is an ectatic disease of the cornea, with progressive thinning and anterior protrusion, eventually leads to an irregular Abstract