Tonometry on the move

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The Tono-Pen

I was impressed by the new version of the Reichert Tono-Pen at this year's Optrafair (Carleton stand) and so was happy for the chance to test it on a few patients. Like the previous version, it is a simple, small hand-held instrument which is gently tapped against the patient's anaesthetised eye. Several readings are taken, which are then averaged out to give an overall reading.

The new unit, called the Avia, is visibly different and has a more ergonomic design, allowing it to be easily gripped penlike to minimise shake error (Figure 1). The instrument has a blue power pack which is simply pushed into the handle ready for use - so there are no longer any awkward battery fittings. To ensure accuracy on initial use (or resetting after a sequence of unusual readings) the instrument needs to undergo a verification process. You simply hold the activation button down for five seconds while the instrument is pointing downwards. Fifteen seconds later, a beep signals that the instrument must be held upright, at which point either 'pass' or 'fail' appears in the small LCD window. Reasons for failing usually involve damage or soiling of the probe tip.