Accuracy and precision of the Tono-Pen in measuring intraocular pressure after keratoplasty and epikeratophakia and in scarred corneas

Arch Ophthalmol. 1988 Dec;106(12):1697-700. doi: 10.1001/archopht.1988.01060140869030.


Intraocular pressure measurements with the Goldmann and Schiotz tonometers are unreliable when the cornea is irregular due to disease or surgery. The Tono-Pen (Oculab, Glendale, Calif) is an electronic applanation tonometer based on the same principle as the MacKay-Marg tonometer. We measured intraocular pressure in 37 eyes with irregular corneas, in 50 eyes that had recently undergone penetrating keratoplasty, in 16 eyes that had undergone epikeratophakia, and in 12 eyes with normal corneas with both the MacKay-Marg and Tono-Pen tonometers. The same two instruments were used, and the sequence of measurement was randomized. Analysis of variance demonstrated no significant difference between measurements obtained with the two tonometers in any of the groups. The data suggest that the Tono-Pen is as accurate as the MacKay-Marg tonometer in those situations where the Goldmann tonometer is inaccurate.

Publication types

  • Clinical Trial
  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Cicatrix / physiopathology
  • Clinical Trials as Topic
  • Corneal Diseases / physiopathology
  • Corneal Transplantation*
  • Evaluation Studies as Topic
  • Humans
  • Intraocular Pressure*
  • Postoperative Period
  • Tonometry, Ocular / instrumentation*
  • Tonometry, Ocular / standards