The noncontact tonometer. Clinical evaluation on normal and diseased eyes

The measurement of intraocular pressure with a noncontact tonometer was correlated to a Goldmann tonometer in 20 normal persons, 20 glaucomatous patients, and 8 patients suffering from corneal diseases. In normal persons the error in measurement for the noncontact tonometer was related to their skill in fixation, and in eye patients to height of pressure and corneal state. Acceptable correlation was found between noncontact tonometry and Goldmann applanation tonometry when the cornea was normal and the pressure below 35 mmHg (Goldmann), otherwise noncontact tonometry was only a guide, and in the presence of corneal disease, unreliable. Good fixation reduced the method error. The standard deviation was 1.09 mmHg at poor fixation and 0.60 mmHg at good fixation. Repeated measurements on the same eye with noncontact tonometry did not alter the intraocular tension.