Influence of Corneal Biomechanical Properties on Intraocular Pressure Differences Between a non-contact ORA Tonometer and the Goldmann Applanation Tonometer in primary congenital glacomatous children

This study aimed at evaluating the effect of corneal properties on the difference between IOP measured with non-contact tonometer (IOPcc) and contact goldman applantation tonometer(GIOP) in children with primary congenital glaucoma(PCG). In current study The influence of central corneal thickness (CCT), keratometry(Km), equicalent sphere of refractive error (ES) and Ocular Response Analyzer (Reichert) measurements of corneal viscoelasticity [corneal hysteresis (CH) and corneal resistance factor (CRF)] on IOP differences between tonometers was evaluated in children with PCG. The CH was calculated to be the best predictor of the differences in IOP readings between tonometers (r2=0.46; P< 0.0001. CRF,CCT,Es and Keratometry performed very poorly as lone predictor of IOP differences. In a multiple regression model CH and CRF together accounted for 84% (r2=0.84; P< 0.0001) of the variance in IOP reading differences between tonometers. Corneal viscoelastic properties (CH) induced by either contact or noncontact tonometers was calculated to be the most determinant factor in influencing IOP differences(IOPcc-GIOP).