Allograft Inlays for Presbyopes

Roibeárd O’hÉineacháin reports

Intrastromal lenticules derived from donor tissue appear to provide a safe, effective, and predictable treatment for presbyopia without the complications associated with pre­vious synthetic corneal inlays, said Dr Arthur B Cummings.

“Corneal inlays have had a chequered past. Nobody can deny that,” he said. “However, we understand the prob­lems, and we know what the issues were. We have learned, and I currently don’t see any corneal inlays that are not al­lografts or biosynthetic collagen, and they now do provide an exciting option.”

When corneal inlays such as the Kamra (AcuFocus) and the Raindrop (ReVision Optics) first came to the European market, refractive surgery clinics advertised the devices as an amazing, quick solution for presbyopia—thousands of inlays were implanted over a couple of years. However, the commer­cially available corneal inlays have since fallen out of favour, mainly because they induce haze that persists after explanta­tion, he explained.

Dr Cummings noted he was the first in Europe to im­plant the Kamra inlay, having implanted 13 of the devices, 7 of which he has since removed. He has also implanted 18 Raindrop inlays, 15 of which he has removed. In a recent survey he conducted of Refractive Surgery Alliance Society members, 65% said they had implanted Kamra and/or Rain­drop inlay before, but 90% said they do not do so currently. On the other hand, 80% said they would use an allograft for presbyopia if it was available.

Previous problems with corneal inlays stem from the poor biocompatibility of the synthetic material used to compose them, he said. In contrast, years of experience with epikera­tophakia have demonstrated the safety and biocompatibility of allografts composed of donor stromal tissue. Moreover, advances in laser and imaging technology and tissue pres­ervation have made it possible to produce sterile stromal lenticules with high precision.

Phase II study yields encouraging results

Dr Cummings and his associates have been part of a phase II prospective multicentre study involving 101 patients who underwent implantation of an Allotex TransForm™ lenticule corneal inlay in the nondominant eye. TransForm obtains the corneal stromal tissue under strict ethical standards from an Eye Bank Association of America (EBAA)-approved eye bank. The tissue is sterilised with electron beam radiation and shaped into the desired dimensions with a femtosecond laser.

The patients in the study were all emmetropic presbyopes who required at least a +1.75 D add to read. The lenticules were 2.65 mm in diameter and 22 microns thick with a +2.5 D add. They were placed under a LASIK flap 110 microns thick and centred visually over a light-constricted pupil.

The 6-month data is available for all 45 patients who received the inlays at Dr Cummings’ centre, and the 12-month data is available for 43 patients. So far, he has removed two inlays because of patient intolerance of the refraction difference between the two eyes, despite a visual acuity of 6/7.5 for distance and N5 for near in the treated eye. A further two eyes have undergone LASIK enhancements, one to increase myopia and the other to decrease it.

The lenticules are easy to manipulate when wet, and— once put in place to dry—they remain securely where positioned, Dr Cummings said. No lenticule moved postoperatively, and when incorrectly placed, they can be easily recentred by lifting the LASIK flap and placing it in the correct position. In addition, the corneas have remained optically clear, and the implants are invisible under the slit lamp.

Overall study results showed that in the treated eye of 34 patients with 12 months of follow-up, decimal un­corrected visual acuity (UCVA) was 0.63 for distance and 0.8 for intermediate and near. In 29 treated eyes with four years of follow-up, UCVA was 0.83 for distance, 0.94 for intermediate, and 0.82 for near.

In terms of safety, none of the treated eyes lost more than two lines of best-corrected distance visual acuity. There was only a 6.6% probability of losing more than one line and less than a 1% probability of losing more than two. In addition, the four-year results in 28 hy­peropes and 29 presbyopes with the TransForm inlay showed that none developed haze, compared to 112 (75%) of 150 eyes with the Raindrop inlay.

“The conclusion from this study is these inlays are very quiet in the cornea,” he said. “There is reduced uncorrected distance acuity in the treated eye on day one, but that improves as the weeks go by. Reading vision improves quicker than distance vision, and binocular distance visual acuity remains unchanged. Moreover, biocompatibility is excellent, and at three years, you still cannot see these inlays under the slit lamp. I see this being used an awful lot more in combi­nation with LASIK.”

Dr Cummings presented his findings at an ESCRS eConnect webinar.

Arthur B Cummings MD, FRCSed, FWRCS is based at the Wellington Eye Clinic, Dublin, Ireland. ABC@WellingtonEyeClinic.com