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How to measure intraocular pressure | VETgirl Veterinary CE Videos

In this VETgirl video, we demonstrate how to measure intraocular pressure (IOP). Here, we demonstrate two common techniques including the newer rebound tonometry and the more traditional applanation tonometry. Prior to performing tonometry, a drop of topical anesthetic such as proparacaine or tetracaine is instilled onto the cornea.

The first device we are using is a rebound tonometer called a TonoVet. This method of tonometry estimates the eye pressure by projecting a small probe from the machine which then bounces off of the cornea. The probe is rebounded back at the machine at a force that is then correlated into the IOP by the tonometer. The machine must be held perpendicular to the surface of the eye. The primary advantage of this method are its ease of use and less surface area contact of the cornea.

The second device is a newer model of Tonopen® called the TonoPen AVIA, which is simply more ergonomic. A disposable cover is placed over the tonometer tip, and should be changed with each patient. The tip is then gently tapped on the surface of the cornea and small tick noises indicate measurements being obtained. The device estimates the IOP by measuring the force required to flatten the small area of cornea.

Regardless of the device used, proper patient restraint is crucial as not to cause false elevation of the IOP with excessive neck restraint, direct pressure on the jugular veins, or excessive eyelid maniuplation. Also, it is important to remember that these are only estimations of IOP. The tonometers report a percent error, which is NOT the accuracy of the measurement but rather the variability between the averaged numbers.

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