TY - JOUR
T1 - Tono-Pen XL® calibration curves for cats, cows and sheep
AU - Passaglia, Christopher L.
AU - Guo, Xiaoli
AU - Chen, Jie
AU - Troy, John B.
PY - 2004
Y1 - 2004
N2 - The objective of this study was to provide calibration curves for correcting intraocular pressure (IOP) measurements obtained using the Tono-Pen XL® tonometer in cats, cows and sheep. Twelve eyes from 9 cats, 13 eyes from 7 cows, 10 eyes from 5 sheep were used. The anterior chamber of the eye was cannulated in vivo, in situ (immediately post mortem) or ex vivo with a fine needle and IOP was varied from 10 to 90 mmHg in steps of 10 mmHg by adjusting the height of a saline reservoir connected to the needle. For each pressure setting, several readings of IOP were made using the tonometer. The relationship between Tono-Pen® reading and manometer setting was linear over the full range of measurement. However, the slope of the data regression line deviated significantly from 1 and indicated that the instrument systematically underestimated IOP. For cats the average slope was 0.62 and for cows and sheep it was 0.72 and 0.69, respectively. For the latter animals, the regression line also had a nonzero intercept of ≈ 4.5 mmHg. Similar results were obtained from in vivo and ex vivo eyes and with different Tono-Pen XL® tonometers. Although developed for use on humans, the Tono-Pen XL® can provide reproducible and accurate measurement of IOP in cats, cows and sheep when suitably calibrated by manometry. The calibration curves provided here, and by implication those reported for other animals using this tonometer, differ in slope from those measured with earlier models of the Tono-Pen®. The reproducibility of the curves we obtained implies that they can be used to correct IOP readings from the Tono-Pen XL® when manometry is not possible.
AB - The objective of this study was to provide calibration curves for correcting intraocular pressure (IOP) measurements obtained using the Tono-Pen XL® tonometer in cats, cows and sheep. Twelve eyes from 9 cats, 13 eyes from 7 cows, 10 eyes from 5 sheep were used. The anterior chamber of the eye was cannulated in vivo, in situ (immediately post mortem) or ex vivo with a fine needle and IOP was varied from 10 to 90 mmHg in steps of 10 mmHg by adjusting the height of a saline reservoir connected to the needle. For each pressure setting, several readings of IOP were made using the tonometer. The relationship between Tono-Pen® reading and manometer setting was linear over the full range of measurement. However, the slope of the data regression line deviated significantly from 1 and indicated that the instrument systematically underestimated IOP. For cats the average slope was 0.62 and for cows and sheep it was 0.72 and 0.69, respectively. For the latter animals, the regression line also had a nonzero intercept of ≈ 4.5 mmHg. Similar results were obtained from in vivo and ex vivo eyes and with different Tono-Pen XL® tonometers. Although developed for use on humans, the Tono-Pen XL® can provide reproducible and accurate measurement of IOP in cats, cows and sheep when suitably calibrated by manometry. The calibration curves provided here, and by implication those reported for other animals using this tonometer, differ in slope from those measured with earlier models of the Tono-Pen®. The reproducibility of the curves we obtained implies that they can be used to correct IOP readings from the Tono-Pen XL® when manometry is not possible.
KW - Cat
KW - Cow
KW - Glaucoma
KW - Intraocular pressure
KW - Sheep
KW - Tonometer
UR - http://www.scopus.com/inward/record.url?scp=3242666824&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=3242666824&partnerID=8YFLogxK
U2 - 10.1111/j.1463-5224.2004.04038.x
DO - 10.1111/j.1463-5224.2004.04038.x
M3 - Article
C2 - 15200622
AN - SCOPUS:3242666824
SN - 1463-5216
VL - 7
SP - 261
EP - 264
JO - Veterinary Ophthalmology
JF - Veterinary Ophthalmology
IS - 4
ER -