EBME Forums Forums Maintenance Technical Assistance Tonometer calibration

Hi Chaps and Chappesses ??

No we're not considering repairs as Clement Clarke will not supply us any parts. We'd certainly save a mint if we could replace all our bent arms!

But before we had the prism and rod, every time a tonometer was dropped it had to be sent back to CC for checking/calibration at £300 at time. At least now we can check to see if damage has occurred. If it's only a calibration issue then we have the specs to work to and bring it back into cal.

Interestingly, we check returning tonometers from CC after repair and they're sometimes out of cal, more than likely due to the TLC they receive at the hands of the post office. These are returned again and eventually they come back and agree with Haag's specs.

The calibration adjustment available is limited to the movement of the counterweight under the top cover. The securing screws are quite small and obviously with a precision instrument undue force is not recommended. - Contrast that to the way they are handled by the ophthalmic guys!

If you still can't achieve calibration then there may be some distortion of the mechanism or contamination of the bearings which will need to be resolved by CC.

However limited, it does allow significant savings to be made along with minimised downtime.

You might also talk to your ophthalmic staff and persuade them into buy a mounting arm for the tonometers which can be swung out of the way when not required. Since these remain permanently attached to the slit lamp there is minimal handling of the tonometer and we have certainly benefitted from them.


All the best

Brian

Hope this helps.

Brian

Hi Brian

I do not want to carry out major repairs on these Tonometers, we have the pressure arm and a prism so are able to do the instrument checks and would like to be able to carry out adjustments when required.

The problem that we frequently see is that the zero point has moved (so instead of -0.05 and +0.05 you have 0 and +0.1). Quite often this is due to the arm being bent, when it is not I presume the counter weight requires adjustment however with no information/instructions we can do not carry out these adjustments.

Lee

Sorry there was a spare "do" in the last line of my previous reply.

Lee

Good old google has produced a clinial paper, authored in the uk in 2005 reporting that "Goldmann applanation tonometers are not as accurate as the manufacturer's recommended calibration error tolerance of +/-0.5 mm Hg would suggest. Calibration error of less than +/-2.5 mm Hg is clinically acceptable. Calibration error checks should be carried out once monthly and tonometers with calibration error greater than +/-2.5 mm Hg returned to the manufacturer for re-calibration"
Do we need this accuracy?? any comments??

Bob..

Bob

This takes us back to the old argument, should you follow the manufacturers instructions or not, and I believe the consensus is that if you don't you better have a good reason (in case of future litigation).


Lee

Yes, Bob. The user should carry out such checks as often as possible. Especially, for instance, after dropping the tonometer on the floor! When it comes to adjusting them (ie, by us), it’s hardly a high-tech bit of kit, is it?

Further to this thread from a few years ago.

Frank lists "Inami - General Maintenance for Tonometer Maintenance manual" under ophthalmology.

If you take a look towards the end of the manual you will find a surprisingly familiar looking Tonometer with instructions on adjustment for calibration.

Lee

HI TO ALL TECHNICIANS,

JUST WANT TO ASK OTHER THAN HAAG STRIET, ARE THERE ANY OTHER COMPANY WHO DOES THE REPAIR AND CALIBRATION OF THE T900?

AMM