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| This is Bonnie showing the proper way to hold and use a tonopen |
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Instructions for Tono-Pen use
Anatomy of the Tono-Pen:
The tip of the pen is extremely delicate, and must always be handled with care. Due to the weight of the tip, it will ALWAYS fall tip down if it is dropped. Wrist bands are available for purchase and are very useful when working with aggressive animals. The button does not need to be pushed with force, but tapped softly.
Calibration:
The Tono-Pen must be calibrated once daily. A ledger of Calibration is wise if there are multiple operators. Frequent daily calibrations are unnecessary and will deplete the batteries. Hold the Tono-Pen tip down with the LED screen facing forward. Tap the button 2 times in rapid succession. The LED will read CAL. After a few moments, the Tono-Pen will beep and the LED will read UP. The Tono-Pen is then switched to the upright position. (The tip is pointed up). The LED will indicate a successful calibration by GOOD and a failure by BAD.
Tip Cover:
The tip cover prevents cross contamination between patients. Always use a new tip cover when measuring intraocular pressure on a patient. The tip cover must be delicately placed on the tip with a loose fit at the top. Wrinkles in the cover at the tip can result in an erroneous reading.
Patient Prep and Restraint
The patient must be held in a position where mobility is limited. Erroneous readings are common and and can be avoided by:
- Giving special care to bracheosephalic patients that require muzzles. Muzzles add pressure on the bottom of the globes.
- Gently holding the eyelids open.
- Monitoring the amount of pressure on the patient's neck.
Only one drop of Proparacaine is required in each eye.
Getting a Reading
GENTLY tap the black button. The LED will show two horizoltal dotted lines. Lightly tap the surface of the cornea. The tip should always be flush with the center of the cornea. The areas closer to the limbus give higher readings. The Tono-Pen will beep each time it registers a reading. After 4 beeps it will average the 4 readings and give a higher tone beep. There are numbers printed on the actual pen, these numbers give the coefficient of variance. Any error over 5% is considered erroneous and must be re-measured.
Proper Maintenance
The Tono-Pen’s battery is good for approximately 600 readings. If the battery keeps loosing charge, it is most likely human error. When the Tono- Pen is stored in the case, make sure the pen is pushed all the way down into the cut out. If the case is closed and the button is exposed, it will be pressed by the lid of the case. This keeps the pen beeping and calibrating which will drain the battery quickly. It is also possible that the pen is being over calibrated by miscommunication between operators. Periodically, the Tono-Pen should be flushed with canned air. This forces any debris that has migrated into the pen to be pushed out. The tip of the pen should be held closely to the output on the can. DO NOT push the tip of the pen onto the can output. Allow 4-5 short bursts of air into the pen. Then calibrate the pen.
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