In Vitro and In Vivo Comparison of Applanation Tonometry and Rebound Tonometry in Dogs

Abstract

ABSTRACT. Intraocular pressure (IOP) evaluated by applanation tonometry via TONO-PEN XL (TP), and rebound tonometry via TonoVet (TV) were compared in enucleated canine eyes with varied pressure of the anterior chamber (AC) and in clinical cases. TV measured IOP values were lower than IOP measurements of TP in the enucleated eyes with 5-10 mmHg of AC (P<0.0001), though there was no significant difference in IOP values obtained with TP and TV on the pressure ranges of 15-20 mmHg. However, TP detected IOP values were lower than IOP measurements of TV in the eyes with over 25 mmHg of AC (P<0.0001). The results of clinical cases were similar to the enucleated eye model. There was no significant difference in IOP values obtained from TP and TV in dogs with normotensive eyes. IOP measurements of TP were lower than those of TV in glaucomatous eyes (P<0.0001). TV was a reliable tonometer for measurement of IOP in hypertensive eyes, whereas it was less accurate than TP in hypotensive eyes. The characteristics of TP and TV should be considered in the evaluation of IOP in practice.KEY WORDS: canine, intraocular pressure, TONO-PEN applanation tonometry, TonoVet rebound tonometry.J. Vet. Med. Sci. 73(12): 1585-1589, 2011 Evaluation of intraocular pressure (IOP) is important for the diagnosis and management of ophthalmic disease in animals [14]. Several tonometries, including indentation, applanation, or rebound tonometry are used to measure IOP in veterinary field [14]. Applanation tonometry, such as TONO-PEN XL (TP), is widely used in the field of veterinary ophthalmology, though it includes potential problems with inaccuracies caused by manual measurement and requires application of a topical anesthetic before IOP measurement [18]. On the other hand, rebound tonometry, such as TonoVet (TV), which has recently become available, is expected to be more reliable than TP, because a constant pressure can be given to the cornea by a mechanically launched probe, thereby providing increased accuracy of IOP measurements [7,10,12]. An added benefit is that topical anesthetics are not needed for detection of the animal's IOP [7,10,12]. There are reports dealing with the usefulness and/or accuracy of TV in animals and birds [1,6,7,[9][10][11][12]. In dogs, TP displayed lower IOP values than TV in in vitro enucleated eyes, although the relation between the two tonometries in glaucomatous eyes was not the same as in vitro [7]. Information about the relationship of IOP evaluated by TP and TV is essential for veterinary practitioners, since the number of veterinary ophthalmologists using both TP and TV has increased recently to assure accurate diagnoses of animals with ophthalmic diseases. The aim of this study is to re-evaluate IOP values measured with TP and TV in the enucleated canine eye model and clinical cases, and to clarify the relationship and characteristics of both tonometries in veterinary practice. MATERIALS AND METHODS Eye samples and clinical cases:Thirty eyes without ophthalmic disorders were immediately enucleated transconj...

Development of tear production and intraocular pressure in healthy canine neonates

“…13 IOP readings in adult dogs, obtained using the same type of rebound tonometer as applied in the current study, ranged between 9.16 AE 3.47 mmHg and 14.2 AE 4.5 mmHg. [22][23][24] In the present study, the initial IOP of 5.6 AE 2.7 mmHg at 2 weeks of age was below or within the lowest reported reference range for IOP in adult dogs. IOP increased significantly to 12.6 AE 1.8 mmHg at 6 weeks of age, which is well within the reported reference ranges for adult dogs.…”

“…The youngest dogs in which IOP was described were 6 weeks of age, and IOP at that age did not differ significantly from IOP one year later . IOP readings in adult dogs, obtained using the same type of rebound tonometer as applied in the current study, ranged between 9.16 ± 3.47 mmHg and 14.2 ± 4.5 mmHg . In the present study, the initial IOP of 5.6 ± 2.7 mmHg at 2 weeks of age was below or within the lowest reported reference range for IOP in adult dogs.…”

Design of an intraocular pressure curve protocol for use in dogs

“…Rebound tonometry has shown a strong linear relationship when compared with results obtained with manometry in enucleated dog eyes (Knollinger et al 2005 ). A separate study using manometry reported that rebound tonometry was reliable in hypertensive eyes (Nagata et al 2011 ). Rebound tonometry gives higher readings than applanation tonometry in dogs with acute glaucoma and an IOP that is >25 mmHg (Slack et al 2012 ).…”

Influence of Age on Ocular Biomechanical Properties in a Canine Glaucoma Model with ADAMTS10 Mutation

“…[ 35 ] Previous studies have shown that the Tono-Pen readings were not significantly different from the Tonovet readings for normotensive eyes. [ 36 , 37 ] Since all IOPs in our previous study were within the range of 10–18 mmHg, these IOP data were combined in the analyses without further conversion. Tonometry was performed on most of the dogs throughout their lifespans ( Table 1 ).…”