A Comparison of the Posner Tonomat and the Mackay‐marg Tonometers

The Posner Tonomat. a newly introduced corneal tonometer based on the applanation prin‐ciple. was compared to the Mackay‐Marg electronic tonometer. The Tonomat was found to correlate well with the Mackay‐Marg tonometer and since it can also be used without anesthesia, it should be a useful addition to the optometrist's instrumentation. It is relatively inexpensive, is entirely mechanical in construction, requires no periodic calibration or servicing, and has disposable end plates that eliminate the possibility of cross infection.