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Transcript of 7 CR Training Short
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CR
The Glaucoma Tonometer
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The Glaucoma Tonometer
What sets it apart?
Reicherts 7CR Auto Tonometer + Corneal Response Technology takes corneal
biomechanical properties into consideration, providing Corneal Compensated IOP (IOPcc) -
a pressure measurement that is significantly less affected by the cornea than other methodsof tonometry.
The 7CR is based on Reicherts patented dynamic bi-directional applanation technology,
which is the foundation of the revolutionary Reichert Ocular Response Analyzer (ORA).
The ORA is the first instrument capable of measuring corneal bio-mechanical properties and
is supported by over 100 peer-reviewed publications in the medical literature.
Corneal properties such as elasticity, viscosity, and thickness can affect the accuracy of
Goldmann IOP values by as much as 17 mmHg in normal eyes and more than 20 mmHg in
eyes with corneal pathology. The ORA, and now 7CR, are the only devices in the world
that can account for these properties.
IOPcc is patented technology (US 7, 481, 767 B2)
Overview
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The Glaucoma Tonometer
What sets it apart?
The 7CR presents you with a tremendous opportunity to sell a unique product that has
strong clinical utility and essentially NO COMPETITION.
7CR is THE Glaucoma tonometer. This is not a screening device, as NCTs were
perceived to be in the past. 7CR should be positioned as the tonometer of choice for the
management of glaucoma for ODs and MDs alike.
The 7CR is superior to Goldmann or any other IOP measurement.
Reichert 7CR Provides more clinically relevant tonometry measurements in:Normal Tension Glaucoma patients(subjects who have glaucoma but measure low on Goldmann)
Primary Open Angle Glaucoma patients(typical high-pressure glaucoma subjects)
Post-LASIK and refractive surgery patients(subjects with biomechanically altered corneas)
Patients with Fuchs or Edema(very spongy corneas that measure inaccurately on Goldmann)
Keratoconus patients(biomechanically weak corneas that measure inaccurately on Goldmann)
Patients with thick, thin, or otherwise biomechanically atypical corneas
Overview
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The Glaucoma Tonometer
Tonometry is used to measure the Introcular Pressure (IOP), which is a risk
factor for Glaucoma. Higher IOP increases the risk for glaucoma.
IOP is the ONLY modifiable risk factor for glaucoma. This means that oncea patient has been diagnosed with glaucoma, the only thing doctors can do
is try to lower the pressure. Regular monitoring of IOP is essential to
determining efficacy of treatment in glaucoma patients.
As such, accurate measurement of IOP is CRITICAL for the proper
diagnosis and management of glaucoma.
Tonometry
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The Glaucoma Tonometer
The Goldmann Tonometer has long been considered the
gold standard for measuring pressure, but its accuracy is
widely questioned today.
Tonometry
Goldmann Design Assumptions
- Cornea is infinitely thin and perfectly flexible
- Tear-film and corneal thickness effect cancel each other out
Flaws- Experimentation done on cadaver eyes (not representative of live eyes)
- Variations in corneal thickness is significantly greater than assumed
- Variations in corneal biomechanical properties unaccounted for
Accordingly, Goldmann cannot compensate for differences in thickness,
elasticity, and other biomechanical parameters that influence accuracy
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The Glaucoma Tonometer
Cant we calculate true IOP using pachymetry (CCT)?
NO!Central Corneal Thickness based IOP adjustment algorithmsDO NOT WORK. These formulas have been scientifically discreditedand the glaucoma opinion leaders of the world are cautioning clinicians
against using them.
As such, CCT correction tables and pachymeters and tonometers thatprovide CCT-based corrected IOP values are OBSOLETE.
Why CCT-based IOP correction is flawed
Correction nomograms that adjust GAT IOP based solely on CCT are neither
valid nor useful in individual patients- Pg 18. Robert N. Weinreb, James D. Brandt, David Garway-Heath and Felipe Medeiros
World Glaucoma Association on Intraocular Pressure; Consensus Series 4; May 5, 2007
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The Glaucoma Tonometer
Why CCT-based IOP correction is flawedOHTS and other recent studies have investigated the relationship between
central corneal thickness (CCT) and IOP values. They have found a
relationship between CCT and GAT measured IOP.
Thicker corneas tendto measure higher on GAT and Thinner corneas tend
to measure lower.
However, the relationship between CCT and measured IOP is only valid
when observing large data sets. When applied to individual patients,
corneal thickness IOP correction formulas present a 40% chance of
adjusting the IOP in the WRONG DIRECTION!
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The Glaucoma Tonometer
Why CCT-based IOP correction is flawed
Data courtesy New England College of Optometry
Very thin corneas tendto measure low IOP
Very thick corneas tend
to measure high IOP
But SCATTER in the data makes accurate mathematical
adjustment of IOP impossible for individuals!
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The Glaucoma Tonometer
Thick and thin is WRONG. Think weak and strong
Why CCT-based IOP correction is flawed
Corneal Resistance to bending is not dependant thickness, but on material properties
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CR
The Glaucoma Tonometer
The 7CR IOPcc measurement is not based on the overly-simplistic Corneal
Thickness correction approach.
7CR quantifies the corneas biomechanical properties, and then reduces the
effect of these on the IOP measurement process
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The Glaucoma Tonometer
Dynamic Bi-Directional Applanation
Goldmann and other tonometers only determine one number, but they
are affected by two things: IOP and cornea.
You cant measure two things with one number!
The 7CR makes a dynamic measurement, monitoring the in/outmovement of the cornea in response to a rapid air impulse.
The Bi-Directional Applanation results in two IOP measurements inrapid succession (one as the cornea moves in, and one as the cornea
moves out). This permits determination of corneal properties, enabling
the 7CR to provide a more accurate IOP measurement.
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The Glaucoma Tonometer
Dynamic Bi-Directional Applanation
Undisturbed
Cornea
IR Light Emitter
IR Light Detector
Auto alignment is achieved. instrument is ready to measure
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The Glaucoma Tonometer
Dynamic Bi-Directional Applanation
Air-JetApplanated
Cornea
IR Signal Peak
Air pulse is delivered, inward applanation is recorded
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The Glaucoma Tonometer
Dynamic Bi-Directional Applanation
Corneal Concavity
Air-Jet
Cornea passes through applanation into mild concavity
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The Glaucoma Tonometer
Dynamic Bi-Directional Applanation
IR Signal Peak
Air-JetApplanated
Cornea
IR Signal Peak
Air pulse reduces, cornea returns, outward applanation is recorded
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The Glaucoma Tonometer
Dynamic Bi-Directional Applanation
Undisturbed
Cornea
IR Light Emitter
Air tube
IR Light Detector
Measurement process complete
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The Glaucoma Tonometer
Applanation Signal Plot7CR Measurement Signal
Inward
ApplanationOutward
Applanation
Corneal
Hysteresis
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The Glaucoma Tonometer
HysteresisHysteresisA property of materials or systems that do not instantly follow
forces applied to them, but react slowly, or do not return
completely to their original state. The phenomenon was identifiedby Sir James Alfred Ewing in 1890. This term is commonly used
to describe material properties in engineering and architecture.
Corneal Hysteresis (CH)
A characterization of thecorneas biomechanical tissueproperties. It is a result of visco-elastic damping (energy
absorption) as the cornea moves rapidly in and out.
This is what enables the 7CR to quantify and minimize the
corneas influence on IOP measurement.Discovered by Dr. David Luce of Reichert Inc
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The Glaucoma Tonometer
HysteresisMany common visco-elastic materials and systems exhibit hysteresis.
- Automotive struts
- Foam mattresses- Viscous fluids like honey and oil
- Door dampers (closers)
The Cornea is visco-elastic like these examples
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The Glaucoma Tonometer
IOPccCorneal-Compensated Intraocular Pressure
IOPcc is patented technology (US 7, 481, 767 B2)
7CR utilizes the information provided in the
Corneal Hysteresis measurement to determineIOPcc, which is less affected by corneal
properties than other methods of tonometery,
such as Goldmann (GAT).
7CR also provides IOPg which is similar to anactual Goldmann measurement. Seeing these
values simultaneously gives clinicians a better
understanding of patient tonometry values.
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The Glaucoma Tonometer
IOPccCorneal-Compensated Intraocular Pressure
IOPcc is still a Goldmann correlated IOP
measurement. It agrees with Goldmann on average,
but is not influenced by the cornea in the same way asGoldmann and other tonometers are.
Therefore IOPcc has the same scale as a Goldmann
measurement, but is more clinically relevant because
it is not contaminated by corneal artifacts.
Note: The PASCAL DCT, which claims independence
from corneal properties is NOT Goldmann correlated.
As such, the clinical relevance of the DCT IOP
measurement is questionable.
h Gl
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The Glaucoma Tonometer
7CR IOPCC vs CCT 184 Normals
Data courtesy New England College of Optometry
IOPcc is not influenced by the thickness of the cornea
Th Gl T t
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The Glaucoma Tonometer
Data courtesy Dr. David Castellano, MD / Dr. Jay Pepose, MD
28 eyes Pre/Post LASIK IOPCC
IOPcc ignores the change in corneal properties cause by LASIK and provides
similar IOP measurements in pre and post refractive surgery subjects
IOPappears to be lower after LASIK
with Goldmann
Th Gl T t
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The Glaucoma Tonometer
Is IOPcc Better than GAT?
Th Gl T t
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The Glaucoma Tonometer
Evaluation of the Influence of Corneal Biomechanical Properties on
Intraocular Pressure Measurements Using the Ocular Response Analyzer.
Felipe A. Medeiros, MD and Robert N. Weinreb, MD
J Glaucoma 2006;15:364370.
Clinical Publications
Conclusions: IOPg agrees with Goldmann very
well. IOPcc seems to provide an estimate of IOP
that is less influenced by corneal properties than
those provided by GAT
IOPg, IOPcc correlation with Goldmann and CCT
GAT
IOPcc
The Glaucoma Tonometer
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The Glaucoma Tonometer
Clinical Publications
Ocular Response Analyzer in Subjects with and without Glaucoma.
Sullivan-Mee M, Billingsley SC, Patel AD, Halverson KD, Alldredge BR, Qualls C.
J Optom Vis Sci. 2008 Jun;85(6):463-70.
In Glaucomatous eyes IOPcc was significantly higher than GAT. Thisrelationship was also true in Glaucoma suspects. However, in normal eyes and
OHT eyes, IOPcc, IOPg, and GAT were all similar.
This indicates that IOPcc is a better indicator of glaucoma presence
IOPcc differentiates Glaucomatous Eyes
The Glaucoma Tonometer
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The Glaucoma Tonometer
Intraocular pressure measured by dynamic contour tonometer and ocular response analyzer in normal tension glaucoma
Tetsuya Morita & Nobuyuki Shoji & Kazutaka Kamiya & Mana Hagishima & Fusako Fujimura & Kimiya Shimizu
Graefes Arch Clin Exp Ophthalmol DOI 10.1007/s00417-009-1169-4
Clinical Publications
Conclusions: Only IOPcc was ableto distinguish the NTG eyes from
the true normal eyes.
IOPcc can differentiate NTG eyes from normal eyes
True normal eyes and eyes with NTG (normal tension glaucoma) were
measured with GAT, DCT, IOPg, and IOPcc
The Glaucoma Tonometer
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The Glaucoma Tonometer
Summary of IOPcc advantagesIOPcc correlates strongly with GAT on the average
HOWEVER, IOPcc has the following advantages over GAT
Not affected by CCT
Not affected by corneal biomechanical properties (rigidity)
As such, it is more accurate in KC, Fuchs, OHT, NTG eyes
In addition, it has less measured IOP reduction post-LASIK
No operator bias
The Glaucoma Tonometer
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The Glaucoma Tonometer
Important Service Note:7 CR cannot be calibrated using rubber eyes like previous
generation Reichert tonometers. A device called a TCT
(Tonometer Calibration Tool) must be used.
Service and calibration training will be provided at another time