Fast-Acting Applanation Tonometers

Introduction In 1885 Imbert1(also cf. Prijot2), set forth the basic theory of applanation tonometry. Two factors stood in the way of a practical solution to the problem: (1) The force against the area of applanation must be large enough to be measured, but the area must not be so large as to raise appreciably the intraocular pressure. (2) The bending force of the cornea and the surface tension of the tears must be obviated or corrected. Goldmann3,4devised a practical solution to the problem by choosing an area of applanation which would satisfy Condition 1 above and at the same time would balance out the opposing forces of Condition 2. Mackay and Marg5approached the solution by employing a sensitive transducer and feedback mechanism to provide a small area of applanation and allowing the bending force of the cornea and surface tension of the tears