June 14, 2016
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New technology may facilitate early detection of diabetes in the OD practice

The ClearPath biomicroscope measures autofluorescence of the crystalline lens, indicating accumulation of advanced glycation end products.

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Clinicians say a new diagnostic technology is allowing them to more quickly identify patients with diabetes and facilitate comanagement with the general practitioner.

Freedom Meditech’s ClearPath DS-120 Lens Fluorescence Biomicroscope received market clearance from the FDA in early 2013 for measuring autofluorescence of the crystalline lens, which, when abnormal, is a marker for diabetes or pre-diabetes.

“The ClearPath DS-120 is an emerging technology and a way for the eye care professional and general practitioner to interact with a dialogue about the diabetic patient, which is good for everyone,” John A. McCall Jr., OD, told Primary Care Optometry News in an interview.

Advanced glycation end products

Individuals with diabetes possess an accelerated accumulation of advanced glycation end-products (AGEs) in tissues, which have been found to be a key mechanism for the ocular, vascular and other complications of diabetes.

Keith D. Ignotz, COO and founder, Freedom Meditech, explained that the sugar binds to the protein of the red blood cell, which is the basis for the HbA1c test to screen for diabetic risk and monitor glucose control.

Likewise, sugar attaches to the crystalline lens proteins in a nonreversible process, he said.

A objective measure of lens AGE fluorescence is displayed on the graph. The green line represents the average normals across the ages 20 to 70 years. A patient measured above the green line, at a specific age, represents increasing diabetic risk. A patient plotted above the red line indicates less than 5% of the patient population would be this way, indicating long episodes of uncontrolled glucose. The curves below indicate the quality of two lens scans in 6 seconds that produce the one fluorescence number plotted on the chart.

A objective measure of lens AGE fluorescence is displayed on the graph. The green line represents the average normals across the ages 20 to 70 years. A patient measured above the green line, at a specific age, represents increasing diabetic risk. A patient plotted above the red line indicates less than 5% of the patient population would be this way, indicating long episodes of uncontrolled glucose. The curves below indicate the quality of two lens scans in 6 seconds that produce the one fluorescence number plotted on the chart.

Image: Freedom Meditech

McCall refers to this insulin product as “tattooing” the lens.

“If a patient has a hyperglycemic event, and sugar exceeds a certain level and ends up in the aqueous, it permanently attaches itself to the lens,” he said. “When sugar ends up in the aqueous, by passing through the blood-aqueous barrier, the patient is deemed pre-diabetic.”

When excited with the blue light the ClearPath emits, the sugar that has attached to the crystalline lens causes a measurable fluorescence effect.

The test is geared toward type 2 diabetes in adults who are unaware of their elevated blood sugar, Ignotz told PCON.

Prior to this technology, eye care providers could detect diabetes only through direct observation of a complication in the retina, which could take 8 to 10 years to present, Ignotz said.

Frederick Cahn, PhD, and fellow researchers determined that the sensitivity and performance of the ClearPath test for type 2 diabetes is comparable to the performance of glucose threshold tests, in a study from the Journal of Diabetes Science and Technology.

The researchers found a sensitivity of 67% at 94% specificity with the test for detecting type 2 diabetes, compared to fasting plasma glucose with a sensitivity of 50% at 95% specificity and to HbA1C with 44% sensitivity at 79% specificity.

Cahn concluded that eye care practices are, “points of care where they may be a public health benefit for screening patients for undiagnosed diabetes.”

John A. McCall Jr., OD
John A. McCall Jr.

ClearPath in practice

The noninvasive test takes only 6 seconds to complete, does not require fasting or patient preparation and is suitable for those without cataract or lens replacement surgery.

In one noteworthy experience with the test, McCall said he administered it on a healthy older female patient in his Crockett, Texas, practice, and the results were abnormal.

“The patient is in good shape, she walks a lot, she’s thin, doesn’t smoke and eats a healthy diet. That’s why she had remained healthy. Her lifestyle had kept her from crossing the line to be diabetic,” he said.

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Without this test, however, her levels would have gone undiagnosed until her condition worsened, he said.

The patient had many questions for McCall after receiving her results, he said. He encouraged her healthy lifestyle, telling her it had delayed diabetes progression.

“When you give a patient that encouragement, they will continue to do everything right,” McCall added.

He reported screening as many patients as possible, including everyone older than 40 years and adults who are overweight. As the test only takes a few seconds, there is no interruption to patient flow, he said. He believes the ClearPath is a way to differentiate your practice.

“Patients love it because they’ve never seen anything like this before,” McCall said. “You’re giving them information they’ve never had.”

The instrument is not currently reimbursed by third parties.

One common challenge that optometrists struggle with is assuring primary care providers of the significance of the test and why the results are worth considering.

“They need a little education, as this is new technology,” McCall said.

He said a few of his colleagues had experiences with primary care physicians who did not understand why an optometrist was recommending they test a patient’s A1c.

“They don’t understand that this new technology exists and can discover history that a single blood test cannot,” McCall said.

It is known that the accumulation of these end products in the lens is a risk for diabetes, but just how much of a risk is unclear, Scott A. Edmonds, OD, FAAO, told PCON. He looks forward to future studies that will examine a large group of people who took the test and failed it and then how many went on to develop diabetes. According to Ignotz, these studies are underway.

Scott A. Edmonds, OD, FAAO
Scott A. Edmonds

“It’s an eye test that we can do as part of the primary health care work-up,” Edmonds said. “When combined with the other risk factors related to social habits and family history and the vital signs of blood pressure and body mass index, it adds to the evidence of chronic diseases, like diabetes, and is a very useful tool for us as primary health care providers. In and of itself it’s just a piece of information that isn’t, as yet, calibrated to make a diagnosis, but rather serves as a significant risk factor for diabetes.”

Ignotz said the technology has been well accepted by leaders in optometry.

“Optometry is the ideal entry point for the detection of the undiagnosed diabetic, when individuals in their late 30s to 50s visit their optometrists, predominantly for reading glasses, and are at the peak of the curve when diabetes risk can be detected prior to complications that can take 10 years to form,” he added.

Ignotz said the company sees the opportunity to develop additional software programs based on studies that could provide a P value for patients at risk of diabetic complications, which would further the ability of the technology to determine the severity and potential duration of uncontrolled glucose for therapeutic intervention. – by Abigail Sutton

Disclosures: Edmonds is a former consultant for Freedom Meditech. Ignotz is chief operating officer and founder, Freedom Meditech. McCall is senior vice president of vendor relations for Vision Source.

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