History and Clinical Validation of the PASCAL® Dynamic Contour Tonometer 81
more precise diagnosis. In the case of glaucoma, eye
doctors seem to have embraced the dramatic evolution of
imaging, where, in the 1950’s the standard of care was
manual disc drawing, to current automated OCT devices
which have retinal and optic nerve resolution of only a
few microns. In the case of visual field measurement, the
1950’s standards were the Tangent Screen and Goldmann
Arc Perimeters. Today, automated devices such as the
Octopus (Haag-Streit) and Humphrey (Carl Zeiss) ana-
lyzers have understandably become clinical standards.
One must ask why, in this world where we have
evolved from the slide rule to sophisticated microproc-
essors which are expected to soon outpace the human
mind, we adhere to the Goldmann “gold standard” in IOP
measurement. Consider that the Goldmann tonometer
was developed in the 1950’s and has well documented
clinically significant systematic errors. While a more pre-
cise technology seems to exist, why has its acceptance
been slow? The answer is probably more economic and
practical then it is scientific. Goldmann tonometers are
relatively inexpensive and tend to be very durable. Addi-
tionally, tonometry as a procedure lacks specific finan-
cial reimbursement in the American insurance system.
While the financial incentive for newer imaging, visual
field tests has helped propel the acceptance of these new
technologies, the financial incentiv e is lacking in the case
of tonometry. It has also been apparent that Ziemer
Group, AG, Switzerland, the manufacturer of the PAS-
CAL®, is a relatively small and unknown to the ophthal-
mic community. This reality has seemed to heighten the
strategic challenges that one would expect in replacing
an age old “gold standard” such as Goldmann applana-
tion tonometry. Given this history, one would hope that a
more precise and reliable technology like the PASCAL®,
with better precision and reliability, will soon become the
new clinical standard in IOP measurement.
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