cr the glaucoma tonometer. what sets it apart? reichert’s 7cr auto tonometer + corneal response...

CR

The Glaucoma Tonometer


What sets it apart?

Reichert’s 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 methods of tonometry.

The 7CR is based on Reichert’s 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


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 NCT’s 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


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 once a 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


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


Can’t we calculate “true IOP” using pachymetry (CCT)?

NO! Central Corneal Thickness based IOP adjustment algorithms

DO NOT WORK. These formulas have been scientifically discredited and the glaucoma opinion leaders of the world are cautioning clinicians against using them.

As such, CCT correction tables and pachymeters and tonometers that provide 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



OHTS 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 tend to 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!



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!


Thick and thin is WRONG. Think weak and strong


Corneal Resistance to bending is not dependant thickness, but on material properties

CR


The 7CR IOPcc measurement is not based on the overly-simplistic Corneal Thickness “correction” approach.

7CR quantifies the cornea’s biomechanical properties, and then reduces the effect of these on the IOP measurement process


Dynamic Bi-Directional Applanation

Goldmann and other tonometers only determine one number, but they are affected by two things: IOP and cornea.

You can’t measure two things with one number!

The 7CR makes a ‘dynamic’ measurement, monitoring the in/out movement of the cornea in response to a rapid air impulse.

The Bi-Directional Applanation results in two IOP measurements in rapid 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.



UndisturbedCornea

IR Light Emitter

IR Light Detector

Auto alignment is achieved. instrument is ready to measure



Air-JetApplanated

Cornea

IR Signal Peak

Air pulse is delivered, inward applanation is recorded



Corneal Concavity

Air-Jet

Cornea passes through applanation into mild concavity



IR Signal Peak

Air-JetApplanated

Cornea

IR Signal Peak

Air pulse reduces, cornea returns, outward applanation is recorded



UndisturbedCornea

IR Light Emitter

Air tube

IR Light Detector

Measurement process complete


Applanation Signal Plot7CR Measurement Signal

Inward Applanation

Outward Applanation

CornealHysteresis


Hysteresis

HysteresisA 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 identified by 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 the cornea’s biomechanical tissue properties. 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 cornea’s influence on IOP measurement.

Discovered by Dr. David Luce of Reichert Inc


Hysteresis

Many 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


IOPccCorneal-Compensated Intraocular Pressure

IOPcc is patented technology (US 7, 481, 767 B2)

7CR utilizes the information provided in the Corneal Hysteresis measurement to determine IOPcc, which is less affected by corneal properties than other methods of tonometery, such as Goldmann (GAT).

7CR also provides “IOPg” which is similar to an actual Goldmann measurement. Seeing these values simultaneously gives clinicians a better understanding of patient tonometry values.


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 as Goldmann 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.


•

7CR IOPCC vs CCT 184 Normals

Data courtesy New England College of Optometry

IOPcc is not influenced by the thickness of the cornea


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

IOP appears to be lower after LASIKwith Goldmann


Is IOPcc Better than GAT?


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, MDJ Glaucoma 2006;15:364–370.

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



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. This relationship 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


Intraocular pressure measured by dynamic contour tonometer and ocular response analyzer in normal tension glaucomaTetsuya Morita & Nobuyuki Shoji & Kazutaka Kamiya & Mana Hagishima & Fusako Fujimura & Kimiya ShimizuGraefes Arch Clin Exp Ophthalmol DOI 10.1007/s00417-009-1169-4


Conclusions: Only IOPcc was able to distinguish the NTG eyes from the true normal eyes.

IOPcc can differentiate NTG eyes from normal eyesTrue normal eyes and eyes with NTG (normal tension glaucoma) were measured with GAT, DCT, IOPg, and IOPcc


Summary of IOPcc advantages

•IOPcc 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


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

cr the glaucoma tonometer. what sets it apart? reichert’s 7cr auto tonometer + corneal response...

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