Fachbereich Veterinärmedizin



    Calibration of the rebound tonometer Tono Vet for the use in birds of prey (2009)

    Reuter, A.
    Müller, K. (WE 20)
    Eule, C. (WE 20)
    Annual Meeting of the European College of Veterinary Ophthalmologists
    Dänemark, 03. – 07.06.2009
    Veterinary Ophthalmology; 12(6, Abstract Nr. 30) — S. 387
    ISSN: 1463-5216
    DOI: 10.1111/j.1463-5224.2009.00712.x
    Klinik für kleine Haustiere

    Oertzenweg 19 b
    Haus 1
    14163 Berlin
    +49 30 838 62356

    Abstract / Zusammenfassung

    Purpose: The TonoVet (Tiolat/Icare, Finland) has already been used for measuring IOP in birds
    of prey. However, data on calibration of the instrument for use in birds are missing, and have therefore
    been the aim of this study. Methods: Ocular health was confirmed intra vitamin. Freshly enucleated
    eyes were cannulated with a 20G-needle and connected to a digital manometer (ATP
    GmbH, Germany). IOP was set at 5 mmHg steps from 5 to 60 mmHg by adjusting the height of a
    NaCl-solution reservoir connected to the needle. At each step, IOP-readings were obtained with the
    TonoVet (internal calibration ‘d’). Regression analysis in SPSS was used to calculate the correlation
    between manometric and tonometric values. Results: The TonoVet increasingly overestimates
    IOP in White-tailed Eagles (Haliaeetus albicilla), Common Buzzards (Buteo buteo) and Goshawks
    (Accipiter gentilis) with increasing IOP. Formulae for regression are as follows: y ¼ )1.20 + 1.60x
    (n ¼ 13 eyes, r2 ¼ 0.992, standard error of the estimate, SEE ¼ 2.54), y ¼ 1.08 + 1.45x (n ¼ 21,
    r2 ¼ 0.994, SEE ¼ 2.07), and y ¼ )1.66 + 1.37x (n ¼ 5, r2 ¼ 0.997, SEE ¼ 1.27), respectively. In
    Eurasian Sparrowhawks (Accipiter nisus) TonoVet values almost represent the ideal line (y ¼
    0.67 + 0.97x, n ¼ 14, r2 ¼ 0.998, SEE ¼ 0.68). In Tawny Owls (Strix aluco) and Long-eared Owls
    (Asio otus), the TonoVet increasingly underestimates IOP with increasing pressure. Regression formulae
    are y ¼ )2.92 + 0.97x (n ¼ 6, r2 ¼ 0.992, SEE ¼ 1.56) and y ¼ )2.30 + 0.80x (n ¼ 4, r2 ¼
    0.997, SEE ¼ 0.84), respectively. Conclusion: IOP values measured with the TonoVet show
    great variations among the different species. In order to interpret tonometric findings, these differences
    need to be considered. Using the presented regression formulae, corrected IOP values can be