Corneal hysteresis is an important indication of the biomechanical properties of the cornea it is an indicator of viscous damping in the cornea during inward and outward applanation pressure events that is the ability of the tissue to absorb and dissipate energy, a property that is determined by the visco-elastic properties of the corneoscleral shell. Abnormalities in corneal hysteresis have been detected in a variety of corneal diseases including keratoconus, fuch’s dystrophy and post lasik surgeries; it is possible to predict which patients stand the greatest risk for postoperative ectasia and other corneal pathologies. Corneal hysteresis can be measured in vivo using Ocular Response Analyzer.