Comparison of the Rebound Tonometer to the Applanation Tonometer for Measuring Intraocular Pressure in Normotensive Rabbits
World Small Animal Veterinary Association World Congress Proceedings, 2009
F.Q. Pereira; A.C.V.R. Almeida; L. Albuquerque; C. Faganelo; J.A.T. Pigatto
Veterinary College, Federal University of Rio Grande do Sul, Porto Alegre, RS, Brazil

The purpose of this work was to compare the accuracy and variability of the rebound tonometer to the applanation tonometer for measuring intraocular pressure in normotensive rabbits. All studies were approved by the institutional Animal Care and Use Committee and were in accordance with the ARVO Statement for the Use of Animals in Ophthalmic and Vision Research. The study population consisted of 60 eyes of 30 New Zealand white rabbits, males or females, and the mean age was 3 months. All patients included in this study received an ophthalmic examination. For all ophthalmic testing, animals were gently physically restrained. Measurements of intraocular pressure were performed with both tonometers. The tonometry was performed by the same examiner and measurements were taken three times for each eye and the average was recorded as the IOP of the animal. Rebound tonometry (Tonovet®, Tiolat, Helsinki, Finland) was performed first and immediately after topical anesthetic drops were instilled in both eyes. One minute after the application of the topical anesthetic, applanation tonometry (TonoPen XL®, Medtronic Solan, Jacksonville, FL, USA) was performed in both eyes. Statistical analysis was performed using paired t tests. A P value of < 0.05 was considered significant. The mean intraocular pressure measurement was 10.35 mmHg (± 1.3) measured by the Tonovet and 18.47 mmHg (± 4.8) measured by the Tonopen. This study demonstrated that the intraocular pressures obtained with the rebound tonometer were concordant with the IOP readings obtained by applanation, but Tonovet values were significantly (p < 0.0001) lower. There was a good correlation between the readings obtained with the Tonovet rebound tonometer and the Tonopen applanation tonometer (r = 0.96). Both tonometers were easy to use. The Tonovet had the advantage of not requiring local anesthetic but the disadvantage of requiring horizontal use while the Tonopen can be used in any position. This study shows that the Tonovet tonometer is a valuable tool in veterinary ophthalmology, useful for measuring the intraocular pressure in the rabbit eye.

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F.Q. Pereira
Veterinary College
Federal University of Rio Grande do Sul
Porto Alegre, RS, Brazil

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