Tonometer validation and intraocular pressure reference values in the normal chinchilla (<italic>Chinchilla lanigera)</italic>.

Abstract: Objectives: To determine accuracy and precision of three commonly used tonometers (TonoVet^® and TonoLab^® (ICare Oy, Finland)—rebound tonometers, and Tono‐Pen VET™ (Reichert, NY)—applanation tonometer) in normal chinchillas, and to establish a normal intraocular pressure (IOP) reference range in this species. Methods: The anterior chambers of three chinchilla eyes were cannulated <italic>ex vivo</italic> and readings obtained at manometric IOPs from 5 to 80 mmHg, using each of the three tonometers in random order. Data were analyzed by linear regression, ANOVA, and Bland–Altman plots. Tonometry was performed in both eyes of 60 chinchillas (age 8 weeks–16.2 years) using the TonoVet^® and relationship between age and IOP analyzed using linear regression. For all statistical tests, <italic>P</italic> < 0.05 was significant. Results: Intraocular pressure values obtained using the Tono‐Pen VET™ and TonoVet^® (in dog calibration mode;‘d’) showed strong linear correlation with manometry within the physiologic and clinically relevant range of IOP (0–50 mmHg). The TonoVet^® ‘d’ setting displayed significantly greater precision over the full range of IOP evaluated than the Tono‐Pen VET™, and both TonoVet and Tono‐Pen VET™ were significantly more accurate than the TonoLab^® tonometer. Mean ± SD IOP (TonoVet^® ‘d’) in chinchillas was 9.7 ± 2.5 mmHg, and the 95% reference interval was 4.7–14.7 mmHg. Conclusions: Both the Tono‐Pen VET™ and TonoVet^® provided clinically acceptable estimates of IOP in chinchillas. The TonoVet^® provides accurate and precise IOP values, while Tono‐Pen VET™ derived measurements showed greater variability. Values obtained either with the TonoLab^® or TonoVet^® used in the ‘unspecified’ calibration setting were inaccurate in this species. [ABSTRACT FROM AUTHOR]