This video shows the view you have when checking eye pressure (glaucoma check) with the goldman applanation tonometer. This device flattens the corneal surface of the eye, and by determining the amount of force required to flatten a measured area, can calculate the inner ocular pressure.
Applanation is one of the harder steps for the beginning ophthalmology student, and can be tricky in patients with sensitive eyes and aggressive blink reflex. Also, it requires that the patient be able to sit up at the slit-lamp, which can be tricky in the infirm and the very young.
Goldman applanation tonometry is based upon the Imbert-Fick principle: such that the IOP measurement can be determined by the amount of force needed to flatten a fixed area of cornea. In this case, we are pushing on the eye with the blue-light applanator, and trying to flatten a round cornea surface with a diameter of 3.06 mm (that’s the area that our variable-force scale is callibrated for).
To ensure we have the correct sized area depressed, the plastic contact point has a prism in it designed such that you know you have the correct size area when the two hemispheres touch (like in these pictures).
Download this video
To download this video, right click on a link below and choose “Save Target As…”
applanationmires.wmv (2.9meg, Windows video file)