Evaluation des Applanationstonometers Tono-Pen Avia^® Vet™ für die Bestimmung des Augeninnendrucks bei Hunden und Katzen

Zusammenfassung

Gegenstand und Ziel Tonometer messen den Augeninnendruck (IOD) nur indirekt, sodass es zu Messungenauigkeiten kommt. Alle Geräte müssen daher durch vergleichende manometrische Messungen für die einzelnen Tierarten kalibriert werden. Im Rahmen dieser Studie wurde das Applanationstonometer Tono-Pen Avia^® Vet™ (TPA) für Hund und Katze kalibriert und ein Korrekturfaktor berechnet. Anschließend wurden anhand einer augengesunden Population Referenzwerte bestimmt und der Einfluss von Alter, Körpergewicht und Geschlecht untersucht.

Material und Methoden Für die manometrische Studie erfolgte bei jeweils 10 enukleierten Hunde- und Katzenaugen eine vergleichende Messung des IOD mit einem Manometer und dem TPA über den Druckbereich von 5–60 mmHg. Anhand der mittleren prozentualen Abweichung zwischen dem mit dem Manometer und dem TPA gemessenen IOD wurden Korrekturfaktoren abgeleitet. Zur Ermittlung von Referenzwerten wurde bei augengesunden Tieren der IOD mit dem TPA gemessen. Die statistische Analyse eines Einflusses von Alter, Körpergewicht und Geschlecht der Tiere auf den IOD erfolgte mit gemischten Modellen.

Ergebnisse Der TPA unterschätzt bei steigendem Druck den IOD zunehmend. Durch Multiplikation des mit dem TPA gemessenen IOD bei Hunden und Katzen mit dem Faktor 1,5 lässt sich der manometrisch bestimmte, reale IOD berechnen. Es wurden 94 Hunde (188 Augen) und 64 Katzen (128 Augen) untersucht. Der Referenzbereich für den mit dem TPA gemessenen IOD beträgt für Hunde 9–18 mmHg und für Katzen 9–20 mmHg. Bei beiden Tierarten hat das Alter einen signifikanten (p = 0,001 bzw. p = 0,008) Einfluss auf den IOD: Mit höherem Alter sinkt der IOD.

Schlussfolgerung Der TPA unterschätzt den wahren IOD bei steigendem Druck. Die Nutzung des berechneten Korrekturfaktors ist bei der Umrechnung des tonometrisch gemessenen IOD in den wahren IOD sinnvoll.

Klinische Relevanz Der TPA eignet sich gut für die Messung des IOD bei Hunden und Katzen.

Abstract

Objective Using tonometers, intraocular pressure (IOP) is merely measured indirectly leading to measurement inaccuracies. All available technical devices are designed for humans, hence a calibration via comparison to manometric measurements is necessary for their use in veterinary medicine. In this study, the applanation tonometer Tono-Pen Avia^® Vet™ (TPA) was to be calibrated for use in dogs and cats resulting in the calculation of a correction factor. Additional objectives were the determination of reference values for TPA-derived IOP and the evaluation of possible influence of patient characteristics on measurements results.

Material and methods For the manometric study, 10 enucleated eyes from cats and dogs were subject to IOP measurement with a manometer and the TPA covering the range of 5–60 mmHg. The mean percentage of difference between manometer and TPA was used to calculate correction factors. Subsequently, the TPA was employed to measure the IOP in healthy animals without signs of ocular disease for the determination of reference values. The effect of the patient characteristics age, body weight, and gender on the IOP measurement results was examined using statistical mixed models.

Results With rising intraocular pressure, the TPA underestimated IOP to an increasing degree. Multiplication of the TPA-derived IOP with the factor of 1.5 for dogs and cats resulted in values well in accordance with the manometrically-derived, actual IOP. In the second part of the study, a total of 94 dogs (188 eyes) and 64 cats (128 eyes) were examined. Reference values for the IOP measured with the TPA are 9–18 mmHg for dogs and 9–20 mmHg for cats. For both species, age exhibited a significant influence (dog, p = 0.001 and cat, p = 0.008) on the IOP measurement results in that the IOP-values displayed a decrease with increasing age.

Conclusion The TPA underestimated the actual IOP with increasing intraocular pressure. The calculated correction factor of 1.5 is suitable for the conversion of tonometric IOP results into actual pressure values.

Clinical relevance The TPA is suitable for the measurement of the IOP in dogs and cats.

Schlüsselwörter

Tonometrie - intraokularer Druck - Manometrie - Auge

Key words

Tonometry - intraocular pressure - manometry - eye

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