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L. Zhong, C. Kos, L. Desai; Comparison of Intraocular Pressure Measurements Between Tonopen Vet and TonoVet in Dutch Belted Rabbits. Invest. Ophthalmol. Vis. Sci. 2009;50(13):2856.
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Dutch Belted rabbits are commonly used for the evaluation of topical drugs to lower intraocular pressure (IOP). The accuracy of IOP measurements, being therefore critical in the analysis of data and subsequent extrapolation to humans, depends on tonometers and techniques. The purpose of this study was to establish the most reliable technique, from two currently available veterinary tonometers, Tonopen Vet and TonoVet, of measuring IOP in Dutch Belted rabbits.
The IOP measurements of 305 healthy Dutch Belted rabbits were performed in the morning at 9:00AM and in the afternoon at 3:00PM with the Tonopen Vet (Medtronic Ophthalmic, Jacksonville, FL USA) and TonoVet (Icare Finland, Panorama Tower, Finland). The measurement range of Tonopen Vet is 5-80 mmHg and each IOP measurement was averaged manually from three continuous readings. The measurement range of TonoVet is 1-99 mmHg and each IOP reading was derived from droping the highest and the lowest of the continuous 6 reading and averaging the remaining 4 reading automatically. All IOP measurements were analyzed by the Student's t-test. After the IOP measurement, the cornea was examined fluororesin staining by a Slit-Lamp.
All IOP measurement range was 16-28 mmHg and the mean IOP of all IOP measurements was 21.74 ± 2.34 mmHg. The mean IOP measurements with Tonopen were 21.61 ± 2.22 mmHg in the left eye and 21.61 ± 2.11 mmHg in the right eye at 9:00AM. The mean IOP measurements with Tonopen were 21.66 ± 2.01 mmHg in the left eye and 21.77 ± 2.01 mmHg in the right eye at 3:00PM. The mean IOP measurements with TonoVet were 21.90 ± 2.77 mmHg in the left eye and 21.73 ± 2.73 mmHg in the right eye at 9:00AM. The mean IOP measurements with TonoVet were 21.92 ± 2.47 mmHg in the left eye and 21.70 ± 2.26 mmHg in the right eye at 3:00PM. There is no significant difference (p>0.05) between the left eye and the right eye at 9:00AM or at 3:00PM either using Tonopen Vet or using TonoVet. There is no significant difference (p>0.05) between 9:00AM and 3:00PM in the left eye or in the right eye either using Tonopen Vet or using TonoVet. There are 5 corneas to find a few positive fluororesin staining using Tonopen Vet and there is 1 cornea to find a few positive fluororesin staining using TonoVet. After 24 hours, all positive fluororesin staining disappeared and no injury on the cornea was found.
There were no great differences in the observations of the IOP measurements using Tonopen Vet and TonoVet tonometers.The mean baseline IOP in Dutch Belted rabbits was 21.74 ± 2.34 mmHg. Both Tonopen Vet and TonoVet tonometers were reliable for measuring IOP in Dutch Belted rabbits without obvious corneal damage.
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