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Tonometer validation and intraocular pressure reference values in the normal chinchilla (Chinchilla lanigera)
Kevin C Snyder1,2, Andrew C Lewin1,2, Christoph Mans1
1Department of Surgical Sciences, School of Veterinary Medicine, University of Wisconsin - Madison, Madison, WI, 53792, USA.
Veterinary Ophthalmology
|March 18, 2017
Summary
The TonoVet® and Tono-Pen VET™ tonometers accurately measure intraocular pressure (IOP) in chinchillas. The TonoVet® offers superior precision, establishing a normal IOP range of 4.7-14.7 mmHg for this species.
Area of Science:
- Veterinary Ophthalmology
- Ophthalmology
- Animal Science
Background:
- Accurate intraocular pressure (IOP) measurement is crucial for diagnosing and managing glaucoma and other ocular conditions in animals.
- Establishing species-specific reference ranges for IOP is essential for reliable clinical assessment.
- Chinchillas are an important animal model in vision research, necessitating validated methods for IOP assessment.
Purpose of the Study:
- To evaluate the accuracy and precision of three common tonometers (TonoVet®, TonoLab®, Tono-Pen VET™) in chinchillas.
- To determine a normal intraocular pressure (IOP) reference range for chinchillas.
- To compare the performance of rebound tonometry (TonoVet®, TonoLab®) versus applanation tonometry (Tono-Pen VET™) in this species.
Main Methods:
- Ex vivo cannulation of chinchilla eyes to obtain readings at controlled manometric IOPs (5-80 mmHg).
- In vivo tonometry performed on 60 chinchillas (age 8 weeks-16.2 years) using TonoVet® and Tono-Pen VET™.
- Statistical analysis included linear regression, ANOVA, and Bland-Altman plots to assess accuracy, precision, and age-related IOP changes.
Main Results:
- TonoVet® (dog calibration 'd') and Tono-Pen VET™ showed strong linear correlation with manometry within the 0-50 mmHg IOP range.
- TonoVet® ('d' setting) demonstrated significantly greater precision than Tono-Pen VET™ across the tested IOP range.
- Both TonoVet® and Tono-Pen VET™ were more accurate than TonoLab®; TonoLab® and TonoVet® (unspecified setting) were inaccurate.
- Mean ± SD IOP measured by TonoVet® ('d') in chinchillas was 9.7 ± 2.5 mmHg, with a 95% reference interval of 4.7-14.7 mmHg.
Conclusions:
- Tono-Pen VET™ and TonoVet® provide clinically acceptable IOP estimates in chinchillas.
- TonoVet® offers accurate and precise IOP measurements, while Tono-Pen VET™ measurements exhibited greater variability.
- The TonoVet® in 'dog' calibration mode is recommended for accurate IOP assessment in chinchillas, establishing a normal reference range.
