TonoLab Tonometer

Introducing the First Tonometer for the Research field

• Does not require the use of topical anesthetic
• Handheld mobile tonometer that has the latest IOP measurement tecnology for the screening of glaucoma
• Has been developed especially for the animal health field
• New probe technology that prevents cross contamination
• There is no risk of microbial contamination, as one-use probes are used in the measurement
• Screening is fast, effective and reliable with documented accuracy
• The TonoLab is designed to take and calculate the average of six measurements, each taken in a fraction of a second, reducing the influence of factors outside of the eye.
• The TonoLab tonometer is used in the diagnosis, follow up, and screening of glaucoma
• The TonoLab is based on the new patented induction based rebound method which allows intraocular pressure (IOP) to be measured accurately, rapidly, and with out a local anesthetic

How It Works

IOP Measurement

PROBLEM:
Measuring Intraocular pressure in rats and mice - Large research efforts have been made in trying to beat glaucoma, a major cause of blindness in the western hemisphere. Early research, which was based on animal studies, suffered due to a lack of methodology to measure small eyes, such as those of rats and mice. The basic research for glaucoma increased when it became possible to measure intraocular pressure (IOP) in the rate eye using the TonoPen. Using a mouse as a model for studies of glaucoma is more preferable because there are many more molecular/biological methods available. It is easier and more economical to maintain mice than larger animals. Mice have similar eye physiology when compared to human eyes. However, the front chamber of a mouse eye contains only 2-4ul aqueous, making it a challenge to measure IOP, First measurements were made in 1997 by cannulating the eye of an anesthetized mouse with a very small needle. This method requires very deep anesthesia which in turn lowers the IOP. Cannulating the eye also damages it and causes infections.

SOLUTION:
A rebound tonometer - A rebound tonometer device for mouse IOP measurement was adapted from prototypes of those originally developed for human IOP measurements. The developed prototype was more accurate than the TonoPen in measuring the IOP of rats. In addition, the goal of measuring IOP from the mouse eye was successful and the prototype was able to measure IOP accurately in vitro and in vivo.

The method is based on impacting a very light probe to the eye at the very low speed (11-13mg, 0.1-0.2m/s)and measuring the motion parameters of the probe during collision to the eye (deceleration, impact time, etc,). The movement energy of the probe is very small (less than 0.25uJ) and most of that is rebounded (not absorbed by the eye) so there is no damage to the eye. Several measurements can be made over a long period of time. It is possible to measure with very light anesthesia so the IOP is not affected. Now Tiolat Oy (Helsinki, Finland) has launched a commercial version of the rebound tonometer "TonoLab" which has been adapted to read rat and mice IOP measurements. The TonoLab, offered by Colonial Medical Supply (Franconia, NH) has several advantages.

Advantages of the TonoLab rebound tonometer:

• Non-invasive measurement with minimal discomfort to the subject.
• The rapid IOP measurements, are instantly display in mmHg.
• The tonometer requires no calibration and features species specific modes for rats and mice.
• The risk of microbiological cross contamination is eliminated with a single use probe.
• The time needed from induction to the instrument to the results of dependable consistent readings is minimal.
• The menu is simple and user friendly providing the researcher with an instrument that is unique, reliable and accurate.

References:

1. Danias J, Kontiola Al, Fillppopoulos T, Mittage T (2003)
Method for the non-invasive measurement of intraocular pressure (IOP) in mice.
Invest Ophthalmol Vis Sci 44:1138-1141

2. Kontiola Al, Goldblum D, Mittag T, Danias J (2001)
The Induction/Impact Tonometer: A New Instrument to Measure IOP in the Rat.
Exp.Eye Res 73:781-785

3. Goldblum D, Kontiola A, Danias J, Chen B, Mittag T (2002)
Noninvasive determination of intraocular pressure in the rat eye.
Comparison of an electronic tonometer (TonoPen), and a rebound (impact probe) tonometer.
Graefes Arch Clin Exp Ophthalmol 240:942-946

4. Ylikarppa R, Eklund L, Sormunen R, Kontiola Al, Utriainen A, Maatta M, Fukai N, Olsen BR, Pihlajaniemi T. (2003)
Lack of type XVIII collagen in anterior ocular defects.
FASEB J 17:2257-2259

5. Wan-Heng Wang, J. Cameron Millar, Iok-Hou Pang, Martin B Wax, Abbot F. Clark. (2005)
Noninvasive Measurement of Rodent Intraocular Pressure with a Rebound Tonometer
IOVS, Dec 2005, Vol. 46, No. 12

6. Amy Knollinger, Noelle La Croiz, Paul Barrett, Paul Miller. (2005)
Evaluation of a rebound tonometer for measuring intraocular pressure in dogs and horses.
JAVMA, Vol 227, No. 2, July 15, 2005

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