A Comparison of Tonographic-Trace Simulations Achieved by Two Systems: Nonlinear Elastic and Linear Viscoelastic

Twenty normal clinical tonographic traces were averaged and compared at 10-s intervals by means of two systems: 1) the decay curves of a linear viscoelastic mathematical model having a single degree of freedom, and 2) nonlinear elastic models, including the classical (or current) Grant model. The linear viscoelastic model provided a considerably better match than the other models. So far as degree of match and facility of outflow values were concerned, the study showed the effect on the models of various investigators' formulations of ocular rigidity, corneal indentation, and tonometer calibration. In precise work facility of outflow values should be reported only if a measure of the degree of fit to the tonogram is given.