Comparison of Oculab Tono-Pen readings obtained from various corneal and scleral locations
J. A. Khan, M. Davis, C. E. Graham, J. Trank and M. M. Whitacre
Department of Ophthalmology, Kansas University School of Medicine, Kansas City 66103.
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.
