Comparison of Goldmann applanation and applanation resonance tonometry in a biomicroscope-based in vitro porcine eye model.

We have developed an in vitro porcine eye model based on a biomicroscope, to simulate a clinical situation for IOP measurement on enucleated eyes. The aims of this study were to evaluate the model and to apply and compare Goldmann applanation tonometry (GAT) and applanation resonance tonometry (ART) measurements in porcine eyes. The GAT measurement (IOPGAT) showed a lower pressure, mean - 14.0 mm Hg (SD = 1.7 mm Hg) as compared with the reference pressure. For in vitro measurement with GAT on porcine eyes the linear calibration was IOP = 1.14 IOPGAT + 12.5 mm Hg (R2 = 0.99, p < 0.001, n = 280, four eyes). ART measurements correlated significantly to reference IOP, R = 0.86 (p < 0.001, n = 252, six eyes), with a mean difference of 5.4 mm Hg (SD = 6.7 mm Hg). GAT could only be used on porcine eyes if the IOP exceeded 13 mm Hg. Evaluation of the ART in this in vitro model showed position dependence for the sensor. To facilitate centre positioning a guiding tool is suggested. Porcine eyes are a possible substitute for human eyes in in vitro models for pre-clinical evaluation of new tonometry methods.