Abstract
Purpose :
The porcine ocular model has been used extensively in ocular research and development. However, assessment of the intraocular pressure (IOP) of this animal model is limited by two critical factors: 1. inaccuracy of available tonometers in the porcine eye without calibration function and 2. the pig has soft and thick cornea which are different from other species that creates a significant challenge. Additionally, no tonometer is designed to measure the porcine IOP, including one of the most advanced rebound tonometers (TonoVet® Plus). The purpose of this study was to calculate actual IOP calibration functions for four available species settings (Canine, Feline, Equine, and Leporine mode) in the tonometer with the enucleated porcine eyes and provide the options to measure accurate porcine IOPs using TonoVet Plus®.
Methods :
Fresh enucleated porcine eyes (n=15) were cannulated with two 20-gage needles into the anterior chamber at the 3 and 9 o’clock areas. One needle was connected to a height-adjustable Balance Salt Solution (BSS) reservoir, and the other was connected to a manometer with a tube. The IOP was measured by TonoVet Plus® with four selections of species at 7.5, 10, 15, 20, 25, 30, 35, 40, 45, 50, and 55 mmHg, respectively (e.g., 15 eyes X 4 species modes X 11 pressure points = 660 measurements). The linear regression was performed for the TonoVet Plus® device with four different modes by plotting the manometric IOP against the reading given by the tonometer.
Results :
A statistically significant (p > 0.05) linear regression was observed from experimental results, and linear functions were calculated for each species’ mode. In the equine mode, the obtained IOP value is well aligned with the true IOP with the manometer (y=1.007x + 0.104, r2 = 0.995, where y = tonometer reading and x = manometer reading). In the feline mode, the tonometer slightly underestimated and overestimated IOP in the lower IOP (7.5 – 15 mmHg) and higher IOP (50 – 55 mmHg), respectively (y=1.077 X – 2.5457, r2 = 0.993). The canine and leporine modes consistently overestimated IOP (Canine: y=1.186 x + 2.2554, r2 = 0.980; Leporine: y=1.382 x + 0.800, r2 = 0.986).
Conclusions :
All species modes could produce appropriate linear functions and presented strong linear trends. Furthermore, using TonoVet Plus® with the equine mode selected provided the most accuracy for measuring pressurized porcine eyes.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.