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In April 1950 Conrad Berens MD and Charles Tolman BS, a consulting engineer, announced in the Journal of the American Medical Association an instrument called ‘Ocular Hypertension Indicator (Tonometer)’. The instrument was designed to allow general practitioners to screen eyes for the presence of pressure elevated above the normal. This would allow them to refer for further investigation and possible treatment those individuals who demonstrated a value above normal, which was set at 25 mm of mercury and thus prevent many eyes from going blind.
The instrument is depicted on the cover of this issue of the BJO. The foot plate of the instrument was constructed to correspond with the popular Schiotz tonometer introduced 45 years previously. There was a free moving central plunger with two closely spaced lines engraved around its top. The …