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by Dr Lachlan Meikle, North Bundaberg Vet Surgery, QLD
The Tono-pen measures intraocular pressure and I use it with virtually all my eye cases. It’s easy to use, ergonomically designed and I find it very handy to get baseline values with each case.
What’s good about it
I believe that eye pressure, along with staining and tear tests, should be part of every eye case that comes into the practice. It’s just like doing a standard TPR. We purchased the Tono-pen because we didn’t have an instrument to measure eye pressure in our clinic.
At a previous clinic where I worked, they had an old school, mechanical Schiotz tonometer. It’s very fiddly to use and difficult to calibrate. The Tono-pen is so user-friendly, we even taught some of our older vets how to operate it and they love it now.
You simply apply some corneal anaesthesia to numb the eye. The animal doesn’t need to be overly restrained which is good as excessive restraint increases the values. Most animals are pretty compliant once the front of the eye is numbed. The Tono-pen is held just like a pen and gently pressed against the surface of the eye.
It has a confidence interval that tells you if it’s accurate or not. You should be aiming at the 95 percentile. If the values are low, it might indicate an inflammatory disease. If the values are high, it might mean glaucoma or some sort of mass in the eye.
What’s not so good
The unit runs on batteries that have to be replaced fairly frequently. It would be better if it was rechargeable and sat in a dock when not in use. It’s not a big issue but it means the practice has to keep buying batteries and keep a stock on hand.