Comparative evaluation of two new applanation tonometers — preliminary study

Three separate intra-ocular pressure assessment preliminary studies utilising the Goldmann, E.M.T. 20 and the Digilab Model 30R pneumatonometer were carried out on a total of 114 eyes with glaucoma, and in 184 normal eyes in 162 patients. In general the E.M.T. 20 gave a lower result than the Goldmann but both compared well within the normal intra-ocular pressure range. Within the normal intra-ocular pressure range the pneumatonometer generally gave a 1–3 mm Hg higher reading than the Goldmann but in the glaucomatous eyes this difference became much less and readings tended to be similar with both tonometers. The fixed calibration of the E.M.T. 20 and its accuracy for pressures in the 20 mm Hg range make it an ideal instrument for screening for glaucoma but it is not suitable for the accurate stabilisation of glaucoma patients under treatment. The accuracy of the pneumatonometer in the range of intra-ocular pressure above 22 mm Hg render it the instrument of choice for the diagnosis and control of glaucoma patients. Added advantages of the pneumatonometer were the resilience of the probe to accidental damage and the ability to record the ocular pulse.