Ex vivo evaluation of Tono-Pen and pneumotonometry in cat eyes.
OBJECTIVE
To evaluate the validity and intraobserver reliability of intraocular pressure (IOP) measurements with both pneumotonometry and the Tono-Pen in a closed ex vivo system in cat eyes.


METHODS
IOP was increased step by step in 5 enucleated cat eyes, while taking IOP measurements with the Tono-Pen and pneumotonometry. The outcomes were compared to readings of a digital manometer simultaneously measuring the actual pressure in the anterior chamber.


RESULTS
Pneumotonometry overestimated IOP below 15 mm Hg and underestimated pressures above 20 mm Hg. Tono-Pen tonometry considerably underestimated IOP over the whole spectrum in all of the eyes tested. The pneumotonometer was identified as the more valid and reliable instrument for cat eyes.


CONCLUSIONS
Both tonometers are clinically useful tools to assess IOP for glaucoma studies using a cat animal model. However, one has to consider underestimation of IOP in the upper ranges. A correction formula can be used to calculate the actual IOP.
Stoiber
Josef
J
Bascom Palmer Eye Institute, University of Miami School of Medicine, Florida 33136, USA.
Fernandez
Viviana
V
Lamar
Peggy D
PD
Hitzl
Wolfgang
W
Fantes
Francisco
F
Parel
Jean-Marie
JM
D000818:Animals; D000867:Anterior Chamber / Q000502:physiology; D002415:Cats; D003936:Diagnosis, Computer-Assisted; D004867:Equipment Design; D007429:Intraocular Pressure; D008365:Manometry; D015588:Observer Variation; D015203:Reproducibility of Results; D014065:Tonometry, Ocular / Q000295:instrumentation* / Q000592:standards