Which are the Optimal Tonometers for Different Animal Species?

—Mice and Rats—

Abstract

To select the optimum type of tonometers for laboratory animals, we tried to record intraocular pressure of Crj: CD-1 (ICR) mice and Crj: CD (SD) rats using a Keeler pulsair, a Topcon tonometer CT-30, a Perkins hand-held applanation tonometer, an Alcon applanation pneumatonograph, and a Tono-Pen XL.

The Keeler pulsair did not show focuses in the operation zone on mice and could focus in the operation zone but not work automatically on rats. The Topcon tonometer CT-30 did not show the alignment points on mice and could not control two points within the inner alignment circle on rats. The Perkins hand-held applanation tonometer did not show half circles of fluorescence on both rodents. The Alcon applanation pneumatonograph was unusable because of the difficulty in immobiliging the animals and the size of the sensor tip on both animals. Although the Tono-Pen XL did not show data with less than 5% error on mice, it could show data with less than 5% error on rats. We perform the repeated observations for 5 days on 5 rats using the same observer. It took 45 to 90 minutes to complete testing of both eyes of 5 rats (5 times/rat/day). The data varied widely within and between animals and days. Furthermore, the value (total mean value 36.6±8.8 mmHg) was somewhat higher than that in references.

We conclude that these tonometers cannot be used for recording intraocular pressure in mice and rats.