Accuracy and precision of the Tono-Pen in measuring intraocular pressure after keratoplasty and epikeratophakia and in scarred corneas
D. S. Rootman, M. S. Insler, H. W. Thompson, J. Parelman, D. Poland and S. R. Unterman
Department of Ophthalmology, LSU Eye Center, New Orleans 70112-2234.
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.
