Photo-pachometer: an instrument for the objective non-contact corneal thickness measurement.

A new instrument to measure corneal thickness is described. The design was based on the well-established optical principle of pachometry and its operation required only basic clinical skills. The instrument measures corneal thickness using a newly developed computer-aided paradigm in order to minimise the inter- and intra-subject variability commonly associated with the original optical technique. Preliminary clinical trials showed that it provides fast, repeatable and objective measurements comparable to ultrasonic pachometry, and no physical contact with the eye was required throughout the procedure. It combines the advantages of the two currently employed techniques and it has potential clinical applications in monitoring the dynamic corneal hydration response in vivo.