Only when the tonometer is at the correct distance and properly aligned with respect to the patient’s cornea, will the image of the corneal reflex fall onto three photodetectors in such a way that more light falls onto the two outer detectors than the central one. At the moment that the instrument senses that the contrast between the sum of the outer and the centre detectors is correct, a valve on the air reservoir automatically opens releasing air onto the patient’s eye. The increasing pulse of air decreases the corneal curvature until it is eventually flattened. At this moment more light falls on the central detector than the sum of the outer two. When this happens the pressure transducer, which is connected directly to the pneumatic system, samples the pulse pressure and the result is digitally displayed
The Goldmann applanation tonometer consists of an applanating probe and weight loaded lever system, which is placed on a slit-lamp mount. The end of the probe is brought into contact with the anaesthetised cornea. When contact is made, the clinician views the applanated area (which is made visibl...
This is a hand held version of the Goldmann tonometer. It uses a spring to exert a variable force upon the eye. It can be used with patients supine or erect. Since it lacks the control and security of a slit-lamp, care must be taken to stabilise the instrument to ensure centration without causing...
This video shows how drugs can be instilled without causing the clinician stress nor the patient anxiety.
