The Tono-Pen. A manometric and clinical study.

A new miniaturized, digital, electronic tonometer, the Tono-Pen (Intermedics, Pasadena, Calif), was evaluated for accuracy and reproducibility of results in the laboratory using enucleated human eyes with an indwelling pressure transducer (manometric study) and clinically using 100 eyes in 50 patients with normal corneas. Reproducibility was good in both the manometric study (SD = 1.09) and in the clinical study (SD = 1.21). Reproducibility of results was similar to that of the MacKay-Marg tonometer and the pneumotonometer in the manometric study, but less than that of the Goldmann applanation tonometer and the pneumotonometer in the clinical study. In the manometric study, the Tono-Pen had less mean error at high pressure ranges than either the MacKay-Marg tonometer or the pneumotonometer. In the clinical study, no statistically significant difference was found between the Tono-Pen and the applanation tonometer at pressures of 10 to 35 mm Hg (the extent of the data spread). In addition to being reliable and accurate, this miniaturized tonometer is portable and easy to use.