Ex Vivo Validation of the TONOVET Plus and TONOVET Pro in Cynomolgus Monkeys (Macaca fascicularis): Comparison of Canine and Lapine Calibration Modes.

OBJECTIVE: To evaluate the accuracy of the TONOVET Plus (TVP) and TONOVET Pro (TVPR) in measuring intraocular pressure (IOP) in ex vivo cynomolgus monkey eyes compared to manometry, and to determine the accuracy of Canine and Lapine calibration modes: ANIMALS STUDIED: Five enucleated eyes from three cynomolgus monkeys. PROCEDURES: The anterior chambers were cannulated to regulate IOP manometrically from 5 to 80 mmHg. Agreement between tonometric and manometric readings was analyzed using a linear mixed-effects model (LMM), Lin's concordance correlation coefficient (CCC), and repeated-measures Bland-Altman analysis. Data points at the 80 mmHg manometric setting were excluded to prevent artificial distortion from the devices' maximum display limits. RESULTS: Strong linear relationships were observed between manometric and tonometric IOPs for all modes. However, the Lapine mode demonstrated proportional overestimation with steeper regression slopes compared to the Canine mode. The Canine mode showed excellent agreement (CCC: 0.967 for TVP, 0.971 for TVPR) with minimal mean bias. In contrast, the Lapine mode exhibited significant positive bias and wider limits of agreement, particularly at higher pressures. CONCLUSIONS: Both TVP and TVPR provided accurate and reliable IOP measurements in cynomolgus monkeys when using the Canine calibration mode. Despite the central corneal thickness of cynomolgus monkeys being closer to that of rabbits, the Lapine mode resulted in significant overestimation and is not recommended. Among the tested settings, the Canine mode provided highly accurate IOP measurements with minimal bias, whereas the Lapine mode significantly overestimated IOP.