Ultrasound device capable of precise imaging, biometry of eye

July 1, 2016

Early results from a repeatability and reproducibility study of a precision ultrasound device indicate the anterior segment imaging device can provide unique measurements on the cornea and will have multiple applications in the future.

Reviewed by Amy Kelmenson, MD

Golden, CO-A new precision ultrasound ophthalmic device (ArcScan Insight 100, ArcScan Inc.) produces finely detailed, highly sensitive anterior segment images, according to the lead investigator at the first of several study sites.

The repeatability and reproducibility testing of the device-which received FDA 501(k) clearance as well as CE Mark approval earlier this year-is taking place in an actual practice setting.

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“The quality and the detail that you see on the images is not something that I’ve seen on other imaging devices before,” said Amy Kelmenson, MD, of Colorado Ophthalmology Associates, Denver. “You can image the entire cornea from limbus to limbus in fine detail, in contrast to some devices that produce a detailed image of just a central area of the cornea.

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“We’re also getting very sensitive images of the entire anterior segment, from the cornea back to the iris, the lens, and even as posterior as the posterior lens capsule,” Dr. Kelmenson said. “You can even see the lens zonules, which I don’t think I’ve ever been able to see on any other anterior segment imaging device.”

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The device is relatively easy to use compared with other types of immersion ultrasound, Dr. Kelmenson observed. Technicians at the clinic required only minimal initial training to become proficient in using the device.

Testing it in clinic

 

Testing it in clinic

Dr. Kelmenson and colleagues at Colorado Ophthalmology Associates received one of the new imaging devices this spring for use in the study.

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The objective is to evaluate intraoperator repeatability and interoperator reproducibility for layered corneal thickness measurements (central cornea, central epithelium, and temporal epithelium) and anterior segment and lens capsule dimensions (sulcus diameter, anterior chamber depth, capsule thickness, and lens rise).

For each patient, each of two operators performed five corneal scans on one randomly chosen eye and five anterior segment/capsule scans on the fellow eye of 20 randomly chosen subjects. This protocol is being followed at the other centers as well.

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“What we’re finding is that it’s extremely repeatable and reproducible,” Dr. Kelmenson said.

Results from the Colorado site are:

  • Central corneal thickness: repeatability 2.3 μm; reproducibility 1.7 μm

  • Central epithelial thickness: repeatability 0.7 μm; reproducibility 0.2 μm

  • Temporal epithelial thickness at a 3 mm radius: repeatability 1.2 μm; reproducibility 0.2 μm

  • Zonular plane diameter: repeatability 130 μm; reproducibility 50 μm

Repeatable measurement has been emphasized as the foundation of the technology and the manufacturer is now collaborating with clinicians to apply what has been learned to improve clinical outcomes and safety.

“We’ve worked hard on the measurement side, and now were focused on the clinical side,” said Andrew Levien, chief executive officer, ArcScan.

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The device-indicated for refractive surgical planning and evaluation of anterior segment pathology-measures anterior chamber depth, angle-to-angle width, individual corneal layers, and sulcus-to-sulcus width, and other metrics.

“It remains to be seen exactly where we can go with the usage of this device,” Dr. Kelmenson said. “There are a lot of applications that this could be used for.”

Multiple applications

 

Multiple applications

Being able to see pathologies that could not be seen before and measure areas of the eye clinicians have not previously measured would help with planning for surgeries, for example.

Epithelial thickness mapping may help in the evaluation of LASIK candidates.

Clinicians could also get a better look at tumors in difficult to visualize areas, Dr. Kelmenson noted.

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“It’s quite different from what we’ve had before, so there’s probably going to be a lot of excitement about the different ways in which it can be helpful in evaluation, diagnosis, and treatment,” she added.

“It’s not a device that does just one thing,” Levien concurred. “We can image many different parts of the eye, so our challenge has always been where do we focus first.”

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The primary motivation of Prof. Dan Z. Reinstein, MD, medical director, London Vision Clinic, London-one of the original inventors of the device technology-was to develop a diagnostic tool for keratoconus evaluation through precision imaging of the epithelium and mapping of changes in its thickness. The epithelium mapping technology has a resolution below 1 μm compared with that of OCT, which is about 3 to 5 μm.

“This technology does it much better than anyone else, and it does it over a much larger corneal diameter than the other technologies do,” Levien said. “Although our long-term focus is imaging behind the iris, including the capsule and periphery, there is much clinical value with unique measurements that we can provide on the cornea today.”

One application could be in improving the evaluation of candidates for LASIK.

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“Approximately 1 in 6 patients who are evaluated for LASIK are turned away, usually because of concerns related to keratoconus, but with careful epithelium mapping using the precision technology of the [device], about two-thirds of those patients can be reconsidered,” Levien said.

The precision imaging of the areas behind the iris will be useful in preoperative planning for sizing and placement of IOLs, particularly as accommodating lens technology advances and surgeons need a more detailed understanding of the anatomy, he suggested.

Using with corneal inlays

 

Discussions have also begun about using the device in pre- and postoperative evaluation of patients undergoing vision correction with a corneal inlay (Kamra, AcuFocus).

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“This is not something we planned for-it’s just in response to current developments in corneal refractive technology and the breadth of our capabilities,” Levien said.

In the posterior chamber, the device could be useful in the relatively small and underserved implantable collamer lens (ICL) market. Accurate sizing is challenging, and other technologies are unable to accurately capture images in the sulcus region, Levien noted.

“We’ll now be able to provide a tool that will allow surgeons to make the measurements with confidence, size the lens properly, and check postoperatively so they know the ICL is not too vaulted and exfoliating pigment off the back of the iris or not vaulted enough and creating premature cataract formation,” Levien said. “It’s really about improving safety and outcomes for ICL.”

As other studies become available and discussions with clinicians continue, Levien said ArcScan will soon have a clearer picture of additional applications for the device.

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Amy Kelmenson, MD

E: akelmenson@gmail.com

Colorado Ophthalmology Associates was compensated for participating in the study.