A NEW TONOMETER - THE PRESSURE PHOSPHENE TONOMETER - CLINICAL COMPARISON WITH GOLDMAN TONOMETRY

Objective: This study aimed to compare the results of pressure phosphe ne tonometry, a new tonometric technique, with Goldmann applanation to nometry. Design: Comparative case series. Participants: A total of 100 consecutive patients (192 eyes) without diagnostic specificity, plus a separate subset of 14 eyes with intraocular pressure (IOP) above 19 mmHg, participated. Intervention: Intraocular pressure was measured wi th Goldmann tonometry by one examiner and pressure phosphene tonometry by a different examiner. There was no communication between the exami ners regarding test results. Main Outcome Measures: Intraocular pressu re. Results: In the group without diagnostic specificity, the mean dif ference between the two techniques was 0.3 mmHg. Fifty-one percent of the measurements were within +/-1 mmHg, 74.9% of the measurements were within +/-2 mmHg of each other, and the average deviation for 100% of the data was 1.8 mmHg. For pressure phosphene tonometry, the mean IOP was 15.2 mmHg with a standard deviation of 2.9 and a range of 18 mmHg (minimum, 10; maximum, 28), With Goldmann, the mean was 15.5 mmHg, th e standard deviation was 3.1, and the range was 20 mmHg (minimum, 8; m aximum, 28). The t test for paired data showed a Gaussian approximatio n with a P Value of 0.05. A comparison between the results of the two techniques gave a correlation coefficient of 0.71. Results for the sep arate 14 patients with higher IOPs yielded a statistically significant mean difference of 0.1 mmHg between the two techniques (P < 0.05, t t est for paired data). For pressure phosphene, the mean was 21 mmHg wit h a standard deviation of 5.5 and a range of 24 mmHg (minimum, 14; max imum, 38). For Goldmann, the mean was 21.1 mmHg with a standard deviat ion of 4.7 and a range of 19 mmHg (minimum, 15, maximum, 34), The corr elation coefficient was 0.73.Conclusions: The close agreement between the two techniques suggests that pressure phosphene tonometry offers a n alternative method for measuring IOP. It has the advantages that it is simple, noninvasive, and inexpensive. Potential uses of the pressur e phosphene tonometer may include self-administered home testing, in o utreach clinics by nonophthalmic technicians, and in patients with cor neal conditions that preclude the use of Goldmann tonometry.