• The Mackay-Marg tonometer has been shown to be an accurate tonometer for the measurement of intraocular pressure in eyes with both normal and diseased corneas. This tonometer is no longer manufactured and has been replaced by the Cavitron Biotronics tonometer that works on the same principle but utilizes a different recording display. The Cavitron Biotronics tonometer's accuracy was compared with that of the Goldmann applanation tonometer in 75 eyes. The Cavitron Biotronics tonometer is not as accurate as the original Mackay-Marg tonometer for individual readings because of wide variations between readings. However, if four readings are taken, the value of the Cavitron Biotronics tonometer that correlated best with Goldmann applanation tonometry was the one reading of the four with the highest value. Using this one value, the Cavitron Biotronics instrument underestimates the true intraocular pressure below 27 mm Hg and overestimates it above this value.
Miller K, Sanborn GE, Jennings LW. Clinical Evaluation of the Cavitron Biotronics Tonometer. Arch Ophthalmol. 1988;106(9):1210-1213. doi:10.1001/archopht.1988.01060140370034