TonoVet Plus (R): Higher reliability and repeatability compared with Tono-Pen XL (TM) and TonoVet (R) in rabbits

Objective To evaluate the accuracy and repeatability of the Tono-Pen XL (TM), TonoVet (R) and TonoVet Plus (R) tonometers by manometric evaluation, and to establish adjustment equations for intraocular pressure (IOP) estimates in rabbits. Animal Studied Rabbits. Procedures A postmortem study was conducted on seven rabbit eyes to verify the correlation between manometry and tonometry with an artificial incremental increase in IOP from 5 and 60 mmHg. A clinical study was conducted to evaluate accuracy and to establish reference values for the species, with measurement of IOP in 17 animals, for 2 consecutive days, with the same tonometers and calibrations used in the postmortem evaluations. Results There were strong linear trends for all evaluated tonometers. In the in-vivo evaluation, the mean IOP values were: 14.23 +/- 1.75 (Tono-Pen XL (TM)); 13.89 +/- 2.07 (TonoVet (R) calibration mode 'd'); 8.88 +/- 1.24 (TonoVet calibration mode 'p'); 18.59 +/- 1.94 (Tonovet Plus (R)). There was a significant difference in the two evaluation times for the two TonoVet (R) calibration modes. The adjustment equations generated from the manometry for the evaluated tonometers were: Y = 0.2570X + 2.219 (Tono-Pen XL (TM)), Y = 0.2289X + 2.389 (TonoVet (R) 'd'), Y = 0.4043X + 4.062 (TonoVet (R) 'p'), Y = 0.1233X + 0.3644 (TonoVet Plus (R)) (X is device-estimated IOP). Conclusions All evaluated tonometers were well correlated with the manometry, with an underestimation of IOP by all devices. Applying adjustment formulas may compensate for systematic errors. TonoVet Plus (R) was well tolerated, and showed better repeatability and reliability in successive evaluations.