Tono-Pen tonometer and corneal thickness

Purpose To compare the intraocular pressure (IOP) measurements taken at the central cornea with those taken at the mid-peripheral cornea using the Ton e-Pen tenometer. Methods Forty-eight normal human subjects had their IOP measurements taken (i) with the Goldmann tonometer, (ii) with the Tone-Pen at the central corn ea and (iii) with the Tono-Pen at the mid-peripheral cornea. The central an d mid-peripheral corneal thickness at the site of IOP measurements were the n determined by ultrasonic pachymetry. Results The mean IOP with the Goldmann tonometer was 15.7 +/- 3.1 mmHg. The mean Tone-Pen IOPs at the central and midperipheral cornea were 15.2 +/- 3 .2 mmHg and 15.7 +/- 3.3 mmHg respectively. The mean midperipheral corneal thickness (578 mu m) was significantly higher than the mean central thickne ss (538 mu m) (p < 0.001). Conclusion There was no significant difference between the IOP taken with t he Tone-Pen and with the Goldmann tonometer. In addition, no clinically sig nificant difference was observed between the IOP readings of central and mi d-peripheral cornea measured by the Tone-Pen.