<prompt> Increased intraocular tension can be diagnosed byTonometerPachymeterPlacidos discKeratometer  <response>: 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 WA. Reference: AK khurana 7th edition 