Comparison of Oculab Tono-Pen readings obtained from various corneal and scleral locations

Arch Ophthalmol. 1991 Oct;109(10):1444-6. doi: 10.1001/archopht.1991.01080100124057.


When estimating intraocular pressure in patients who are uncooperative or who have central corneal disturbances, the physician may find it either impractical or undesirable to place the small tip of a portable electronic applanation tonometer (Tono-Pen) over the central cornea. To gauge better the usefulness of Tono-Pen readings obtained from various locations, we compared such readings measured through the central cornea, midperipheral cornea, limbal cornea, and sclera of 15 cannulated eye bank eyes. Mean Tono-Pen readings from the midperipheral and clear limbal cornea did not differ significantly from central corneal readings over a 10- to 35-mm Hg range of intraocular pressures and were within +/- 2.4 mm Hg of mean central corneal readings. Mean readings taken from the sclera, however, were 8.8 to 17.0 mm Hg higher than mean central corneal readings over the 10- to 40-mm Hg range. We concluded that multiple noncentral corneal readings with the Tono-Pen provided a useful approximation of intraocular pressure, whereas scleral readings did not.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cornea / physiology*
  • Humans
  • Intraocular Pressure / physiology*
  • Reproducibility of Results
  • Sclera / physiology*
  • Tonometry, Ocular / methods*