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Cheryl Guttman Krader is a contributor to Dermatology Times, Ophthalmology Times, and Urology Times.
Device in FDA trial for patients with corneal opacity, high risk of penetrating keratoplasty complication
Drawbacks and limitations of penetrating keratoplasty and penetrating keratoprosthesis prevent their widespread use to treat the tens of millions of people with corneal blindness. A nonpenetrating artificial cornea was designed to overcome the impediments.
Reviewed by Yichieh Shiuey, MD
Science fiction may be closer to science fact for an investigational non-penetrating artificial cornea (KeraKlear, KeraMed) as an alternative to penetrating keratoplasty. The advancement could ultimately help eliminate corneal blindness, said Yichieh Shiuey, MD, practicing cornea and refractive surgeon, Palo Alto Medical Foundation, Sunnyvale, CA, and inventor of the device.
The flexible keratoprosthesis is implanted into a corneal pocket in a straightforward, minimally invasive, in-office procedure that removes the people in the world affected by corneal blindness never have any opportunity for treatment to restore vision,” Dr. Shiuey said. “There exists a big mismatch between the availability of corneal tissue for transplantation and the number of patients in need of a corneal transplant, and yet very few artificial corneas are being implanted.”
There is also a lack of trained corneal transplant surgeons worldwide and few sterile operating rooms that are properly equipped for the procedure, he added.
“Although the Boston keratoprosthesis offers an alternative to corneal transplantation, donor tissue is still needed for implantation,” Dr. Shiuey said. “It is associated with severe complications that limit it from being widely utilized,” he said. “If we could change this dynamic, we could potentially treat all of the patients in the world who are affected by corneal blindness.”
The non-penetrating keratoprosthesis has an overall diameter of 7 mm and has a 4 mm central optic.
“The optic provides a full visual field and its prescription is also potentially customizable,” Dr. Shiuey said. The device is implanted through a 3.5 Î¼m trephination incision into an 8-mm corneal pocket that is created at about 100 Î¼m above the endothelium using a femtosecond laser.
“The keratoprosthesis cannot be implanted without a very precise way to make the corneal pocket, and so the pocket cannot be created manually,” he said. “The recommended method of pocket creation is with a femtosecond laser, which is widely available around the world,” he said. “For those places that do not have access to femtosecond lasers, there are commercially available non-laser devices that can be used for precise pocket creation.”
RELATED: OCT and OCTA: Seeing deeper into sickle cell retinopathyThe procedure does not need to be performed in an operating room, nor does it require concomitant glaucoma surgery that is often performed in cases of penetrating keratoprosthesis implantation, Dr. Shiuey emphasized. “The procedure can be performed in a clean office environment, and it has a short learning curve,” he said.
A review of outcomes in 26 patients who were previously blind showed that 92% were able to achieve 20/200 or better vision. Improvement in vision occurred quickly after surgery, stabilized within one to two months, and remained unchanged during a mean follow-up at 50 months.
The safety review showed an 11% extrusion rate. Other complications included one case of corneal melting in a patient with a diagnosis of chemical burn and one infection in a patient who was not compliant with the postoperative regimen.
“There were no cases of endophthalmitis, retroprosthetic membrane, or increased IOP, which are the serious complications that traditionally happen with penetrating keratoprostheses,” Dr. Shiuey said.
The outcomes were replicated in another series reported by Jorge Alio, MD, PhD, that included 15 patients [Alio JL, et al. Br J Ophthalmol. 2015;99:1483-1487].
“There were also no cases of endophthalmitis, retroprosthetic membrane, or increased IOP in this smaller cohort,” noted Dr. Shiuey, adding that Dr. Alio also commented that the “Kera Klear keratoprosthesis is a noninvasive viable alternative to corneal transplantation with potential advantages like decreased risk of endophthalmitis, expulsive hemorrhage, and worsening glaucoma.”
The development of the non-penetrating keratoprosthesis is supported in part with funding from the National Institutes of Health.
The FDA trial is investigating its use in patients with corneal opacity that are at high risk of complications with penetrating keratoplasty. The study is being conducted at four U.S. centers, including Harvard Medical School; the Gavin Herbert Eye Institute, University of California-Irvine; Duke Eye Center; and the Cincinnati Eye Institute. Dr. Shiuey encouraged his colleagues to refer potentially eligible patients for screening.
Yichieh Shiuey, MD
This article was adapted from Dr. Shiuey’s presentation during the Innovators General Session at the 2019 meeting of the American Society of Cataract and Refractive Surgery. As the inventor, Dr. Shiuey has a financial interest in the KeraKlear artificial cornea.