Increased intraocular tension can be diagnosed by

The intraocular pressure (IOP) is measured with the help of an instrument called tonometer. Two basic types of tonometers available are: indentation and applanation. Indentation (impression) tonometry is based on the fundamental fact that a plunger will indent a soft eye more than a hard eye. The concept of applanation tonometry was introduced by Goldmann is 1954. It is based on Imbe- Fick law which states that the pressure inside a sphere (P) is equal to the force (W) required to flatten its surface divided by the area of flattening (A); i.e., P = W/A. Reference: AK khurana 7th edition