Several questions of interest arose in connection with tonometric measurements in the glaucoma clinic of the Long Island College Hospital (Dr. Henry Mitchell Smith, director). Would it be possible, for instance, to determine whether the reliability of the measurements would be enhanced by use of the Schiøtz instrument or by use of the McLean instrument? Could a table of equivalents be arranged with which to check one instrument against the other, so that, given a reading with one instrument, one could with reasonable certainty judge the probable reading with the other? And, finally, was one instrument more reliable than the other when used on eyes with low tension, normal eyes and eyes with high tension?
A study of 205 eyes was made, without full knowledge of the work of other observers, in an effort to solve these questions. It then seemed well to review the field of tonometry from Schiøtz'