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Evaluation of three applanation tonometers in dogs
D R Priehs1, G G Gum, R D Whitley
1Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville 32610-0126.
American Journal of Veterinary Research
|October 1, 1990
Summary
The Mackay-Marg tonometer demonstrated the highest reliability for measuring intraocular pressure (IOP) in dogs across a wide range. Other devices showed varying accuracy, with Tono-Pen overestimating low IOP and underestimating high IOP.
Area of Science:
- Veterinary Ophthalmology
- Ophthalmology
- Comparative Medicine
Background:
- Accurate intraocular pressure (IOP) measurement is crucial for diagnosing and managing ocular conditions in animals.
- Applanation tonometry is a common method for IOP assessment, but device reliability can vary.
- In vivo evaluation of tonometers in a canine model provides valuable comparative data.
Purpose of the Study:
- To evaluate the in vivo accuracy and reliability of the Mackay-Marg, Tono-Pen, and Challenger applanation tonometers.
- To compare tonometric IOP measurements with direct manometric IOP measurements in canine eyes.
- To assess tonometer performance across a broad range of intraocular pressures (5-100 mm Hg).
Main Methods:
- Six clinically normal dogs were used, with 12 eyes evaluated.
- Tonometric IOP measurements were taken using Mackay-Marg, Tono-Pen, and Challenger devices.
- Measurements were compared against closed manometric IOP readings from the anterior chamber under anesthesia.
Main Results:
- The Mackay-Marg tonometer showed the highest reliability (r2 = 0.996) across the 5-100 mm Hg IOP range and excellent reliability (r2 = 0.962) between 10-30 mm Hg.
- The Tono-Pen tonometer was reliable (r2 = 0.967) but showed a tendency to overestimate low IOP and underestimate high IOP.
- The Challenger tonometer was reliable (r2 = 0.965) but lacked accuracy due to a poor linear correlation.
Conclusions:
- The Mackay-Marg tonometer is the most reliable device for in vivo IOP measurement in dogs within the tested pressure range.
- Tono-Pen and Challenger tonometers exhibit limitations in accuracy and linearity, particularly at extreme pressure values.
- These findings inform the selection of appropriate tonometers for canine ophthalmic examinations.