Bb. Fresco, A NEW TONOMETER - THE PRESSURE PHOSPHENE TONOMETER - CLINICAL COMPARISON WITH GOLDMAN TONOMETRY, Ophthalmology (Rochester, Minn.), 105(11), 1998, pp. 2123-2126
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.