Bioengineered corneal inlay overcomes biocompatibility problems of past technologies
The material is a biosynthetic collagen that naturally integrates in the corneal environment.
A corneal reshaping inlay made of biosynthetic collagen to correct presbyopia is under study in Europe.
“Corneal inlays for presbyopia have been around for some years. I tried them all but was skeptical from the start,” Pavel Stodulka, MD, PhD, said in an interview with Ocular Surgery News.
From an optical standpoint, the idea was excellent, and results were good in terms of gaining reading vision, but the cornea was unable to tolerate the implants in the long term. Corneal scarring often occurred in the interface as a reaction to the synthetic material.
“I thought that if the concept worked and the material was the problem, then it was a matter of finding a biocompatible material,” Stodulka said.
Together with LinkoCare, a Swedish company that manufactures artificial corneas made of biosynthetic collagen, Stodulka designed a presbyopic inlay made of that material.
“We are now getting ready to start the CE mark study. I have performed the first surgeries outside Europe, and the results are excellent. All eyes implanted with this inlay achieved uncorrected J1 vision, and binocular reading vision is very good. We have 1 year of follow-up, and results are stable, with no interface reaction. So, I believe we got there,” Stodulka said.
A straightforward procedure
“The biosynthetic approach has the advantage of not being dependent on corneal donor tissue,” Stodulka said, referring to another presbyopic inlay under study by Allotex.
Stodulka is an investigator for the Allotex study, as well.
“It works nicely, and I am sure it has a bright future ahead,” he said. “However, [the biocompatible material] is a more widely accessible technology, easier to produce for a market that is potentially quite huge.”
Implantation of the LinkoCare inlay is performed through a corneal pocket made by a femtosecond laser. The tiny inlay is stained with trypan blue to make it more visible during surgical manipulation, which is easy and straightforward, lasting for no more than 30 seconds, Stodulka said. The procedure is potentially reversible.
“You can quite easily access the pocket and remove or exchange the lenticule. We never had a reason to do this, but it is theoretically, and for sure also practically, a possibility,” he said.
The procedure aims at correcting presbyopia by increasing the refractive power of one eye for reading vision. The inlay is typically implanted in the nondominant eye to make the cornea steeper in the center. The increase in thickness is 15 µm and creates a keratometry increase of 3.3 D, “more than enough for a comfortable, uncorrected J1 reading,” Stodulka said.
“We have developed our own algorithm to process all the Pentacam (Oculus) data for corneal shape change. The highest change rate is in the center, tapering toward the periphery,” he said.
Barely distinguishable within the cornea
As for all procedures that induce monovision, some time is required after surgery for adaptation to a different mechanism of vision. A typical disadvantage that should also be considered is the loss of some distance vision. However, to optimize distance vision and spectacle independence, the dominant eye can be treated with any of the classic refractive surgery methods before implantation of the inlay in the nondominant eye.
The bioengineered material is so similar to human collagen that it is barely distinguishable within the cornea, even by the highest-resolution OCT.
“It is almost impossible to visualize it. We can see it on the slit lamp if we illuminate it from the side, but generally it is almost indistinguishable inside the cornea. It has also the same refractive index,” Stodulka said.
He has no concerns about potential long-term biocompatibility issues with this implant. The material has 8 years of history as an artificial cornea, during which it was well tolerated in all eyes.
“I foresee that the LinkoCare inlay will find its way into the market as a novel option for presbyopia in emmetropic patients or low hyperopes up to +1.5 D. This on condition that they accept monovision, which is something we should discuss and test in advance with our patients,” he said. – by Michela Cimberle
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- Pavel Stodulka, MD, PhD, is director and head surgeon at Gemini Eye Clinics in Zlin and Prague, Czech Republic, and Vienna, Austria. He can be reached at email: firstname.lastname@example.org.
Disclosure: Stodulka reports he is a paid investigator for LinkoCare and owns shares in the company and is an investigator for Allotex.