Abstract
Purpose: :
To determine the accuracy and reproducibility of intraocular pressure (IOP) measurements obtained with the TonoVet® (TV) rebound tonometer (Tiolat Oy, Helsinki, Finland) in cynomolgus monkeys.
Methods: :
The anterior chamber of each eye of 3 ketamine+pentobarbital anesthetized cynomolgus monkeys (Macaca fascicularis) was cannulated with branched, 23-gauge needles. One branch of each needle was attached to a vertically adjustable reservoir, and the other to a pressure transducer, for measurement of manometric (‘true’) IOP. IOP was increased by 5 mmHg increments from 5 to 70mmHg, and then decreased by 10mmHg decrements to 10mmHg. At each increment and decrement, IOP was measured using the TV, by 2 independent observers. IOP was also measured at 10mmHg increments from 5 to 65 mmHg and from 70 to 10mmHg, by a single experienced observer, using a Goldmann applanation tonometer (GAT).
Results: :
Readings taken with both the TV and GAT correlated strongly with manometric IOP (slope=0.972 and 0.917, respectively) and had comparable accuracy. No significant inter-operator difference was observed for the TV. GAT readings were significantly more precise than those taken with the TV (r2 coefficients=0.984±0.005 vs. 0.955±0.005 respectively; p=0.0017). TV readings taken while decreasing IOP were significantly closer to true IOP (p≤0.004) compared to TV readings taken while increasing IOP. IOP readings taken with the TV in the right eye were significantly closer to true IOP (p<0.034) vs. those taken with the TV in the left eye, however TV measurements for right and left eyes were not significantly different. The TV had a non-significant tendency to underestimate IOP, and this tendency was greater for increments than decrements (2.13 vs. 0.945 mmHg, respectively).
Conclusions: :
In normal cynomolgus monkeys the TV can be considered a reliable alternative to GAT since it allows accurate, precise and reproducible IOP readings to be obtained while requiring minimal corneal contact and no topical anesthetic.
Keywords: intraocular pressure