Constant Pressure Applanation Tonography With the Mackay-Marg Tonometer

Abstract

Several years ago it was pointed out that it would be desirable to keep tonometric pressure in the eye constant during tonography in order to eliminate the necessity of estimating or assuming ocular rigidity.¹ For this purpose a method employing a Schiotz tonometer whose plunger weight could be varied appropriately according to the 1955 tonometer calibration was developed. Since then the calibration of the Schiøtz tonometer has been questioned.^2-5 Therefore, a system of constant pressure applanation tonography which promised to be more easily calibrated has been devised. This first report deals with the device which has been developed and with early results of its use. Future papers will deal with clinical results in greater detail. Materials and Methods The flat end of the Mackay-Marg tonometer probe modified to 8 mm diameter is used for two purposes: as an applanation device and as a pressure sensor (Fig 1). The