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Multifunction Tonometer – FAT1TM
The New Standard
Slit Lamp Mounted, Cleared by the FDA for Tonometry, Ocular
Pulse Amplitude, Tonography, and Ophthalmodynamometry
1. Tonometry - IOP Measurement
fluorescein, No Subjective Mire Alignment
Measurements in 3 Seconds
Variation of IOP with Cardiac Cycle – True IOP
Resistance and Wetness Compensation
Pulse Amplitude Measurement
Outflow of Aqueous Humor
Decreased Outflow in Glaucoma
is Directed at Increasing Outflow to Lower IOP
Measurement Useful for Glaucoma Management
Pulsatile Force of Central Retinal Artery
Retinal Artery Pressure Decreased in Vascular Disease
Estimate Ocular Perfusion Pressure, Important in Glaucoma
5. Single Use
Standard of Care, Eliminate Infection Risk, Enhance Your
Laboratory Trials Summary:
In a clinical trial comparing of the Falck Medical Multifunction
Tonometer (FAT1) in 205 eyes
the following results were obtained:
In a comparative study of the FAT1 readings to a reference
u-tube mercury manometer using human eye bank eyes, the
following results were obtained:
Tonography Trial Summary:
In a clinical trial comparing the FAT1 to a reference
indentation tonographer for the measurement of conventional
outflow facility in 91 eyes from 91 subjects the following
results were obtained:
conventional outflow facility (C) difference between the
FAT1 and the reference Indentation Tonographer over a range
of 0.01 to 0.70 ul/min/mmHg was 0.0043 ul/min/mmHg ( 95% CI,
0.001 to 0.0076 ), n= 182.
conventional outflow facility measurement in the glaucoma
group was 0.09 +/- 0.05 and in the non-glaucoma group was
0.31 +/- 0.12 ul/min/mmHg, p < 0.0001, n = 182.
IOP measurement in the glaucoma group was 20.02 +/- 5.5 and
in the non-glaucoma group was 18.6 +/- 2.4, p = 0.01, n =
In the High
outflow facility group (C > 0.18) (non-glaucoma, 28/30 eyes)
93.3% of the paired differences were within +/- 1.96
standard deviations of the mean difference between the FAT1
and the reference Indentation Tonographer, n=60.
In the Medium
outflow facility group (C >0.09 < 0.18) (glaucoma, 29/31
eyes) 95.2% of the paired differences were within +/- 1.96
standard deviations of the mean difference, n=62.
In the Low
outflow facility group (C < 0.09) (glaucoma, 30/30 eyes)
96.7% of the paired differences were within +/- 1.96
standard deviations of the mean difference, n=60.
Laboratory Study Summary:
In a comparative tonographic laboratory study using freshly
enucleated preserved eye bank eyes, the following results were
For every 10
mmHg change in IOP average anterior chamber fluid volume
change was 3.22 ul/minute, for a 20 mmHg change in IOP
average anterior fluid volume change was 7.027 ul/minute and
for 30 mmHg change in IOP average anterior fluid volume
change was 11.75 ul/minute, r2 = 0.99.
correlation coefficient for volume decrease and corneal
indentation was 0.999.
correlation coefficient for volume decrease and applanation
diameter was 0.997.
Ophthalmodynamometry (OPH) Study Summary:
In a clinical trial involving 42 adult eyes where ipsi-lateral
OPH force, brachial artery blood pressure and IOP were recorded,
the following results were obtained:
OPH estimated Central Retinal Artery Force was 59.73 +/-
Brachial Artery Blood Pressure (MBAP) was 93.16 +/- 8.32
IOP was 15.72 +/- 3.04 mmHg.
calculated Ocular Perfusion Pressure was 44.01 mmHg.
*Results on file with the Food and Drug Administration
New Multifunction Applanation Tonometer Device Which Can Be Used
as a Risk Assessment Tool in the Management of Glaucoma and
Vascular Disorders Published in CFOCEO Magazine on
03/21/2016. Click on this link to read full text of the
The FAT1 device
was cleared by the Food and Drug Administration on
01/15/2016 for market introduction with the following
indications for use: Tonometry, Ocular Pulse Amplitude,
Tonography and Ophthalmodynamometry
82 year old male presented with a history of Branch Retinal Vein
Occlusion in the supero-temporal quadrant of his left eye. On
examination arteriolar narrowing and arterio-venous compression
was noted. The OCT image demonstrates thinning and loss of
normal architecture in the supero-temporal quadrant. Mean
Central Retinal Artery Pressure (MCRAP) and
Ocular Perfusion Pressure (OPP) were measured using
the Ophthalmodynamometry Function of the FAT1
With normal vascular physiology and normal vessels, in the
upright position MCRAP should be equal to or greater than
60 % of ipsi-lateral Mean Arterial Brachial Blood Pressure (MABBP).
Ocular Perfusion Pressure (OPP) is the difference
between MCRAP and IOP. Ocular Perfusion Pressure
is the net force that drives blood flow into the eye (Adlers
Physiology of the Eye, Clinical Application, Tenth Edition,
Chapter 33, Ocular Circulation, page 764-765).
The measured ipsi-lateral MABBP was 106 mmHg, 60% of this value
is 60.6 mmHg. The FAT1 measured MCRAP was 52.8 mmHg which is
less than expected and the OPP was 36.2 mmHg which is also less
than expected. See FAT1 Ophthalmodynamometry Result Screen. In
the FAT1 Ophthalmodynamometry study, in healthy eyes the Average
Ocular Perfusion Pressure was 44.01 mmHg. Both values are
less than expected, documenting decreased retinal perfusion from
the BRVO and atherosclerosis.
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Click to Enlarge and to Close
Amaurosis Fugax , Carotid
An 80 year old male presented with an episode of temporary
vision loss in his right eye one week ago. No plaque or other
emboli were found on examination. Using the
Ophthalmodynamometry Function of the FAT1 Device, Mean Central
Retinal Artery Pressure (MCRAP) and Ocular Perfusion Pressure (OPP)
Measured Mean Ipsilateral Arterial Brachial Blood
Pressure (MABBP) was 89.3 mmHg. Sixty percent of this value is
53.6 mmHg. Measured Mean Central Retinal Artery Pressure (MCRAP)
was less than expected at 44.9 mmHg. Ocular Perfusion Pressure (OPP)
was also less than expected at 32.1 mmHg.
See the FAT1
Ophthalmodynamometry Result Screen.
Because the history and the FAT1 results were suggestive of
carotid vascular disease, an intracranial Magnetic Resonance
Imaging Arteriogram was performed which confirmed
atherosclerotic carotid vascular disease and raised the
possibility of an anterior communicating artery aneurysm. See
the MRA report. A CTA was scheduled for further evaluation.
The CTA confirmed an anterior communicating artery aneurysm.
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Click to Enlarge and to Close
An 57 year old male with Pigmentary Glaucoma in
the right eye presented with elevated Intraocular Pressure (IOP).
Current medications were Combigan BID, Pilocarpine 1% TID,
Travatan QHS and Diamox 500 mg BID. On gonioscopy the angle was
open with 4+ pigment. Laser Trabeculoplasty was performed. The
IOP remained elevated at 30 mmHg well above the target value.
Heidelberg Retinal Tomography documented progressive thinning of
the nerve fiber layer at 6 and 12 o’clock. See the HRT results.
The Tonography Function of the FAT1 Device was used to
assess Trabecular Meshwork Aqueous Humor Outflow.
Aqueous Humor Outflow was reduced at 0.109 microliters /
minute and the ratio of the IOP (Po) to Outflow (C), Po / C
Ratio, was 204.6. See FAT1 Tonography Results Screen.
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Click to Enlarge and to Close
In the FAT1 Tonography Clinical Study, Glaucomatous eyes had an
Outflow Value less than 0.18 microliters / minute. A Po / C
ratio greater than 100 is characteristic of glaucomatous eyes
(Chandler and Grants Glaucoma, Fourth Edition, Chapter 6,
Tonometry and Tonography, page 45 - 48).
Visual field testing was performed. The decreased outflow
facility, which did not respond to medical or laser surgery, was
the cause of the elevated IOP. The patient underwent a
trabeculectomy to bypass the dysfunctional trabecular meshwork.
The Tonography function of the FAT1 device was
used to assess aqueous humor outflow after the trabeculectomy
procedure. Outflow was increased to 0.745 microliters / minute,
confirming the effectiveness of the trabeculectomy.
See the post-trabeculectomy procedure FAT1 Tonography Results
/ Pupillary Block
year old male presented with an intumescent count fingers
cataract in the right eye. Pupillary block was present. On
direct gonioscopic examination the anterior chamber angle
was closed at Grade 1. In the left eye and the anterior
chamber angle was open at Grade 4.
The Tonography function of the FAT1 device was used to
assess aqueous humor outflow through the trabecular
meshwork. It was reduced to 0.044 microliters / minute and
the Po / C ratio was increased at 327.3. See the FAT1 Tonography Results Screen for the Right Eye.
In the left eye, the aqueous humor outflow was 0.203
microliters / minute and the Po / C ratio was 88.7. See the
FAT1 Tonography Results Screen for the left eye.
One percent Pilocarpine was placed in the right eye and a
YAG Laser Peripheral Iridectomy was performed. The pupillary
block decreased and the anterior chamber angle deepened to
Aqueous humor outflow was assessed post-iridectomy using the
Tonography Function of the FAT1 Device. It increased to
0.374 microliters / minute, confirming the effectiveness of
the iridectomy. See the post-iridectomy FAT1 Tonography
with Current Tonometer Technology, Review of Published Peer
Applanation Tonometer is based upon a proven physical principle,
the Imbert-Fick Law. Use of this law to measure intraocular
pressure has major drawbacks, which were identified by Professor
Goldmann in his original publication: “On Applanation Tonometery
by H. Goldmann and T. Schmidt, published in Ophthalmologica 134,
publication was translated from German into English with the
assistance of Pamila Seiving, Former Head Librarian, University
of Michigan Kellogg Eye Center, and Holger Hansen, M.D., Dr. P.H.,
Professor of Community Medicine, University of Connecticut
School of Medicine. What follows are excerpts taken from the
original text, which identify the issues and limitations
associated with Applanation Tonometry.
important to recognize that non-contact tonometers are not based
on the Imbert-Fick Law and therefore are not applanation
tonometers. The question to ask is what physical law do they use
to estimate eye pressure? No known proven physical law
validating the methodogy of non-contact tonometers can be found
in the published literature. They also do not have the ability
to compensate for any of the measurement errors that Dr.
Goldmann so aptly described.
Corneal Wetness, Thickness and Elasticity
“Imbert-Fick’s Law States that the pressure of a fluid sphere,
that is surrounded by a thin membrane can be measured by a
counter pressure, which flattens the membrane. His necessary
condition is that the membrane is extremely thin and without
stiffness and that no other factors are involved”, page 221.
“The 0.5 mm
thick cornea represents by no means an extremely thin membrane
without stiffness… The surface of the cornea is moistened by
fluid. Consequently, capillary forces will operate when the
cornea is flattened, depending on the moistening fluid and the
adhesive properties of the flattening device and the cornea”,
number of new problems arise which the abstraction of
Imbert-Fick’s law does not take into account”, page 222.
has the (dimension) characteristics of pressure and, therefore
acts as additional pressure”, page 223.
assumed thus far that K1 (rigidity factor)
is an expression of completely elastic forces. But because the
cornea represents a rheological system, it should be presumed
that it “floats” under the influence of deforming forces, i.e.,
after prolonged impact of those forces the cornea gains a new
balance … One can see that in this experiment (Table VII and
Figure 9), the tonometrically measured pressure declines in
spite of manometrically constant pressure… This is an expression
of floating of the cornea”, page 232.
circumstances that vary much from our measurement conditions
(abnormally thin or thick cornea, e.g. keratoconus, animal eyes,
epithelial edema) errors of several millimeters are to be
expected”, page 241.
As stated by
Dr. Goldmann, The Goldmann tonometer cannot measure and
therefore cannot compensate for the forces due to corneal
wetness, thickness and elasticity. These forces affect the
accuracy of all tonometers including non-contact tonometers.
Current tonometer technology cannot measure the forces due to
corneal wetness, thickness and elasticity. Therefore, the
current technology cannot compensate for these forces, which
limits the accuracy of the measurement.
Solution: The FMAT1 optical and force generation system measures
the forces due to corneal wetness, thickness and elasticity. The
device compensates for these forces, eliminating the measurement
errors associated with use of the Imbert-Fick Law.
Intraocular Pressure Variation due to the change in Diastolic
and Systolic Blood Pressure
recognizes the coincidence of the two half rings (Fig 13) but
some general technical expertise is necessary because eye
pressure varies with the pulsating blood pressure. With correct
measuring position, one can see the two half rings moving across
from each other, with the inner margins of the half rings moving
equally far to the left and the right” , page 240.
more since the quickly established eye pressure does not reflect
the natural average eye pressure at the time of measurement. The
natural average eye pressure at a given point could be
recognized only if one could control constant changes due to not
only the pulse wave and breathing but also the impact of the
outer eye muscles, the changing tension of the lids and
emotional influences” , page 241.
The Goldmann tonometer does not measure the variation in
intraocular pressure (IOP) that occurs with the cardiac cycle.
IOP is higher in systole than diastole. The pulsating mires of
the Goldmann Tonometer are evidence of this. When the inner
edges of the mires are aligned, that is the diastolic phase of
the cardiac cycle. This can be confirmed by checking the radial
pulse when the inner edge of the mires are aligned, which is the
end point according to the instruction manual. The mires
separate during systole and cannot be aligned. The Goldmann
tonometer cannot and does not measure IOP during systole.
average individual spends one-third of the time in systole and
two-thirds in diastole. Because the Goldmann tonometer cannot
measure the systolic IOP, the measurement is not a true average
IOP. One third of the IOP data is not being measured.
tonometers are not measuring the true average IOP as well. They
lack the ability to determine at what point in the cardiac cycle
data is being captured. The data capture is random. So a true
average IOP is not being measured.
true average IOP is the combination of the IOP during systole
blood pressure is measured both the systolic (SBP) and diastolic
(DBP) is recorded. From those two values, the mean arterial
pressure (MAP) is calculated, ((2DBP + SBP) / 3) = MAP.
Solution: The FMAT1 optical system is able to determine what
phase of the cardiac cycle the measurement is captured. The
device measures the IOP during systole and diastole for several
cardiac cycles and calculates a true average IOP. The Ocular
Pulse Amplitude (OPA) is the variation in IOP with the cardiac
cycle. The FMAT1 device measures and displays the true average
IOP and the OPA.
Repeatability, Precision and Accuracy
Repeatability in a measurement system refers to the ability of
an operator to consistently repeat a measurement with minimal
variation. Precision is how close the measurements are to each
other. The closer repeat measurements are to each other, the
less the variation. Accuracy is how close a measured value is to
the actual true value.
So the only
way you can obtain an accurate measurement is to take multiple
repeat measurements, calculate the average or mean value and
calculate the variation. An accurate measurement should have
tonometer only takes one measurement, and it is subjective
because the user has to line up the scale. So the measurement is
affected by the experience of the user and the subjective
alignment of the measurement scale, which causes measurement
bias. With only one measurement, it is not possible to determine
the accuracy of the measurement.
tonometers also have the same issue. Multiple measurements must
be taken over time, averaged and the variation examined to
determine if the measurement is accurate.
decisions are made based upon the measured value, it is
critically important that the measurement be repeatable, precise
It is not possible to determine the accuracy of a measurement
with current tonometer technology. With only one measurement
value, the repeatability, precision and accuracy of the measured
value cannot be determined.
Solution: The FMAT1 device samples every millisecond for
multiple cardiac cycles. The sample data is analyzed for
repeatability, precision and accuracy. The mean and percent
variation is displayed to the user for his/her assessment.
Transmission of Infectious Disease
studies have confirmed infectious prions in the tears of
individuals with Creutzfeldt – Jakob Disease (Mad Cow), HBV
virus in the tears of Hepatitis – B infected individuals, HCV
virus in the tears of Hepatitis – C infected individuals and
HTLV virus in the tears of individuals infected with the AIDS
virus, (Br J Med Res 2014 Apr 30;4(12):2322-2333, J Infect Dis
2012 Aug 15;206(4):478-485, J Clin Microbiol 1995 Aug 33(8):
2202-2203, Ophthalmology 1986 Dec 93;12:1479-1481). For these
potentially lethal diseases, the infectious agent is present in
the tears before the infected individual manifests the disease.
time, Hepatitis-C is the leading cause of death among all
infectious diseases in the US, as reported by Kathleen N. Ly,
MPH, CDC Division of Viral Hepatitis, (Clinical Advisor, June
2016, Page 14).
studies examining the disinfection efficacy of different
regimens for tonometers have found that none are 100 % effective
at removal of the Hepatitis-B Virus, Hepatitis-C Virus and the
AIDS Virus. Studies also confirm that the infectious prions of
Creutzfeldt-Jacob Disease (Mad Cow) are resistant to all
conventional forms of sterilization, (Am J Ophthalmology 2001
Feb;131(2):184-187, Br J Med Res 2014 Apr 30;4(12):2322-2333,
Arch Ophthalmol 1994 Nov;112(11):1406-1407, Arch Ophthalmol 1989
in the United States on individuals with Creutzfeld-Jakob
Disease (Mad Cow) have confirmed that tonometry is a risk factor
for infection: Ocular Tonometry and Sporadic Creutzfeldt-Jakob
Disease: A Confirmatory Case-Control Study, Br J Med Res 2014
Apr 30;4(12):2322-2333. The study conclusion was that due to
lack of effective disinfection regimens and confirmation that
tonometry is a risk factor for infection, disposables are
Lethal infectious agents of Hepatitis B, Hepatitis C, AIDS and
Creutzfeld-Jakob (Mad Cow) Disease are present in tears.
Disinfection regimens, even if they are followed, do not
eliminate these pathogens.
Additionally, contact tonometers can be used without
confirmation of disinfection. They can also be used with or
without disposable covers. There is no absolute requirement that
they must be disinfected before use, or that a disposable cover
is used, or that the disposable cover has been changed after it
has been used. There is also no means of preventing reuse of a
disposable cover or disposable probe.
Air-puff tonometry once thought to be the solution, is not. It
is also a risk factor for transmission of infectious disease.
Laboratory studies have demonstrated that the puff of air
disperses the tear layer causing micro-aerosol formation. “The
ease with which droplets, potentially contaminated with human
immunodeficiency virus and other viruses, are dispersed is
disturbing. Air-puff tonometry may not be aseptic as previously
presumed”, (Microaerosol Formation in Non-Contact Air Puff
Tonometry. Britt JM, et al. Arch Ophthalmol 1991
micro-aerosols are dispersed in a cloud which are inhaled,
deposited on external surfaces and deposited on the external
surface of the eye. This creates the potential transmission of
infection to not only other patients from contaminated surfaces
but directly to staff from inhalation of the infectious
micro-aerosols or deposition on the ocular surface.
Solution: The FMAT1 device uses a disposable plastic prism. The
prism must be changed before a measurement can be performed on a
different patient. The device has a detection system that is
able to determine if the prism has been used. It is an absolute
barrier to the transmission of infectious disease.
information in this article is the property of Falck Medical,
Inc., 07/16/16 Copyright 2016
Advisory Board Members:
Francis Y. Falck, Jr., MD, PhD, MS, Assistant
Clinical Professor, University of Connecticut School of
David Epstein, MD, Professor and Chair,
Department of Ophthalmology, Duke University School of
Elias Reichel, MD, Vice Chairman,
Department of Ophthalmology, Tufts University School of
Research Presentations with Falck Medical, Inc
Clinical Comparison of the Falck Medical
Tono-Ophthalmodynamometer (FAT Model 1)
Calibrated Weight Indentation Tonography. Agency for
Healthcare Research and Quality. Department of Health and
Human Services. Comparative Effectiveness of Screening for
Clinical Comparison of
the Falck Applanation Tonometer (FAT Model 2) to Goldmann
Applanation Tonometer. Agency for Healthcare Research and
Quality. Department of Health and Human Services.
Comparative Effectiveness of Treatment of Glaucoma.
Macular Society Meeting, 02/2010. Anti-VEGF
Injections Decrease Ocular Perfusion Pressure.
Association in Research in Vision and Ophthalmology
Meeting, 05/2010. Anti-VEGF Injections and Ocular
World Forum 2010, Cambridge
University, 08/2010. Strategies for Preventing Blindness.
World Glaucoma Congress, Paris, France , 07/2011.
Anti-VEGF Injections Independently Increase Intraocular
Pressure and Decrease Ocular Perfusion Pressure.
Association for Research in Vision and Ophthalmology,
05/2000. Falck Medical Applanation Tonometer Intraocular
Pressure Measurements, Corneal Thickness and Corneal
Dr. Francis Falck, Chief Executive Officer,
Falck Medical, Inc received the “2010 Man of the Year in
Medicine and Healthcare Award” at the World Forum 2010,
Cambridge University, Cambridge, England on August 18th,
Dr. Falck was recognized for his milestone
work developing diagnostic technology that will be used
worldwide to prevent blindness and stroke.
World Forum 2010 was attended by 150 scholars from 40