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The general dissatisfaction with the tonometer as a dependable clinical instrument is being voiced with increasing frequency. Its continued employment is justified in that the only other method of estimating pressure, digital palpation, gives results even less accurate and less interpretable.
In 1929-1930 I had occasion to examine for mechanical defects about 100 tonometers of various makes. The great majority of these instruments showed such grave imperfections as to render them well nigh worthless as diagnostic aids. No report of this study was made because the data were too incomplete and the investigation was supplementary to a larger problem, that of "optical tonometry." On careful consideration of the subject, it is obvious that a purely optical means of studying intraocular pressure is highly desirable. No mechanical contact should exist between the eye and the recording device, as the irritation of any foreign substance probably modifies the balance of ocular