Optovue adds another product to its iVue platform: software for corneal epithelial mapping.

If you already own an Optovue iVue OCT, you know what it can do, and what it could do: at purchase, you have the OCT. And after, should you desire, you can add a fundus camera to the iVue platform.

And now Optovue has developed software to map epithelial thickness that can be installed in the iVue platform. This FDA-approved product allows assessment of corneal conditions or surface irregularies in pre- and post-surgical patients undergoing refractive procedures and corneal crosslinking.

Already commercially available in Europe, Asia and Canada, corneal epithelial thickness mapping (ETM) is available at minimal cost to those who own the iVue, says Qienyuan Zhou, PhD, vice president, Clinical Affairs, Optovue.

“We recognized the clinical need for mapping of the cornea and corneal surface irregularity, and this technology demonstrates the capability of Optovue OCT technology to noninvasively assess the corneal epithelium quantitatively,” says Dr. Zhou. “Large area mapping of the corneal epithelium was not possible before in a routine clinical setting. Corneal confocal microscopy has been used before, but it has a different application and purpose and much smaller imaging area.”

HOW IT WORKS

The mapping works similarly to routine examination using OCT on the cornea. The scan center can be aligned to the eye’s pupil. The software detects the cornea’s anterior and posterior boundaries, in addition to the corneal epithelial boundary. From these three boundaries, three thickness maps involving the cornea are generated: epithelial; stromal; and full corneal thickness.

There is no contact with the cornea, and scan acquisition takes about one second, says Dr. Zhou, adding that the software is easy to use. “There is not much of a learning curve in terms of acquiring the scans,” she says. “Clinical application involves the interpretation of the information in the maps.”

The only limitation to using the device would be with patients who cannot keep their eyes steady for at least one second, explains Dr. Zhou. “In such a case, as with any imaging technology, the quality of the data may not be reliable.”

VIEWS LIKE NO OTHER

Researchers like George Asimellis, PhD, asssociate professor of Optics and Visual Science, University of Pikeville/Kentucky College of Optometry, Pikeville, have been waiting for corneal epithelium mapping for a long time.

“[The iVue] has the unique ability to create cross-sectional images and thickness maps of ocular tissue,” says Dr. Asimellis, who has been involved in corneal ETM research in Europe for several years. “No other technology today can do that. An abnormality in the stroma, for example, cannot be detected or imaged by other ocular imaging devices. Since the epithelial layer partially compensates for stromal irregularities, the topography or tomography data, obtained with other modalities, do not accurately represent the status of the corneal stroma in such cases.”

He says ‘it’s a must” that every corneal specialist should examine the epithelium. The software can detect differences in epithelium thickness variations across the cornea; and differences in the stroma.” The technology, he says, is sensitive and specific and provides clinical guidance not available.

Further, Dr. Asimellis adds, the corneal ETM software is operator-independent, removing the subjectivity from scanning.

OUTCOME REMEDY?

Procedures such as PRK and laser-assisted sub-epithelial keratectomy (LASEK) — laser eye surgeries designed to correct vision and leave patients spectacle and/or contact lens-free — do not always produce the targeted outcomes.

The medical literature shows that variable wound healing responses may contribute to the occasional unpredictable outcomes that have been produced after PRK and LASEK, notes Mihir Parikh, MD, chief surgeon at NVISION Eye Center of La Jolla/San Diego, Calif., and past-president of the San Diego Medical Society.

“The corneal epithelium can have peaks and valleys or an irregular contour to it prior to undergoing keratorefractive surgery,” says Dr. Parikh. “This can be caused by medical conditions such as dry eyes that were not detected and optimized pre-operatively. When PRK/LASEK is then applied to the irregular corneal surface, a biological cascade of events may occur in the healing phase that results in epithelial hyperplasia to ‘fill the valleys’, and an unexpected refractive surgery outcome.

“Similarly, if a patient is undergoing an enhancement surgery with PRK and the corneal topography is irregular after the first procedure, then in the recovery phase, the cornea may respond with epithelial hyperplasia which will result in an unintended outcome.”

With Optovue’s ETM technology available to pinpoint corneal epithelial irregularities, clinicians can identify patients who would be at-risk of having suboptimal outcomes after laser surgery, explains Dr. Parikh.

“The software could be a screening or a diagnostic tool that can guide us when to proceed with LASEK or PRK,” he says. “We cannot see the corneal epithelium with just a topography map. Before we perform the PRK/LASEK [procedural] enhancements, we can optimize the corneal epithelium with additional pre-operative therapy.”

Various interventions can be performed to make the epithelium more robust and to avoid “surprise” refractive results, says Dr. Parikh.

For example, if a patient has pre-existing dry eye, that condition should be managed before refractive surgery. Says Dr. Parikh: “Put the patient on artificial tears or prescription medications or possibly an amniotic membrane that can normalize the tear film and improve the corneal epithelium.” OM

Financial disclosures: Dr. Parikh is a clinical investigator for Optovue. Dr. Asimellis, not a paid consultant, has used Optovue’s ETM software for investigative purposes.