May 2005
Volume 46, Issue 13
ARVO Annual Meeting Abstract  |   May 2005
Abstract Title: An Evaluation of the TonoVet® Rebound Tonometer for Measuring Intraocular Pressure in Dogs and Horses
Author Affiliations & Notes
  • A.M. Knollinger
    Eye Care for Animals, Salt Lake City, UT
  • N.C. La Croix
    Eye Care for Animals, Salt Lake City, UT
  • P.M. Barrett
    Eye Care for Animals, Salt Lake City, UT
  • P.E. Miller
    School of Veterinary Medicine, University of Wisconsin–Madison, Madison, WI
  • Footnotes
    Commercial Relationships  A.M. Knollinger, None; N.C. La Croix, None; P.M. Barrett, None; P.E. Miller, None.
  • Footnotes
    Support  Comparative Ophthalmic Research
Investigative Ophthalmology & Visual Science May 2005, Vol.46, 4845. doi:
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      A.M. Knollinger, N.C. La Croix, P.M. Barrett, P.E. Miller; Abstract Title: An Evaluation of the TonoVet® Rebound Tonometer for Measuring Intraocular Pressure in Dogs and Horses . Invest. Ophthalmol. Vis. Sci. 2005;46(13):4845.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract: : Purpose: Until recently, all commercially available tonometers used in domestic mammals have been optimized for the human eye and require the use of topical anesthesia. Hence, they may not only inaccurately estimate IOP in these species, but the frequent application of topical anesthesia can also confound anti–glaucoma drug screening in animals. The new, commercially available, TonoVet tonometer uses the motion parameters of an induction/impact (I/I) probe as it rebounds from the cornea to create species–specific calibration curves. The effects of greatly differing globe sizes and corneal physical characteristics on the accuracy of this instrument, however, have not been documented. We compared TonoVet rebound tonometric IOP estimates from a common laboratory animal used in glaucoma drug screening (dogs) and a domestic mammal with a very large eye (horses) to those obtained with the Tono–PenVET® applanation tonometer and a manometer. Methods: In vitro: Using enucleated eyes from dogs (n=10) and horses (n=6) TonoVet IOP estimates were compared to "open" manometric readings over the range of 5 to 80 mm Hg in 5 mm Hg increments. In vivo: IOP estimates were obtained from 100 normal dogs and 35 normal horses using both tonometers in various orders. Results: Canine and equine IOP rebound tonometric estimates were highly linear (r2 = 0.99) and closely paralleled manometric IOP in both species. In general, TonoVet IOP differed from manometric IOP by only 2.1% in dogs and 4.7% in horses. Tonometer order did not alter IOP estimates in living animals. Normal mean (± SD) IOP with the rebound tonometer was 10.8 ± 3.1 mm Hg (range 5 – 17 mm Hg) in dogs, and 22.1 ± 5.9 mm Hg (range 10 – 34 mm Hg) in horses. Tono–PenVET applanation tonometer readings in the same animals were 12.9 ± 2.7 mm Hg (range 8 – 18 mm Hg) in dogs, and 21.0 ± 5.9 mm Hg (range 9 – 33 mm Hg) in horses. Application of the TonoVet tonometer to the eye of living horses and dogs in the absence of topical anesthesia failed to elicit a perceptible response by the animal. Conclusions: The TonVet rebound tonometer accurately estimated IOP in normal canine and equine eyes, which differ greatly in size and corneal physical characteristics, and allowed for tonometry in these species without topical anesthesia

Keywords: intraocular pressure 

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