38 48 FACTORS AN AFFECTING ALLOGRAFT OR SMILE BIOSYNTHETIC OUTCOMES CORNEAL 40 44 RINGS? NEW LENTICULE ALLOGRAFT EXTRACTION CORNEAL AND PLATFORMS BIOSYNTHETIC INLAY IMPLANTATION 34 IN PRESBYOPIA 46 SMILE: ALLOGRAFT LATEST CORNEAL INLAY AND LIMITS FOR HYPEROPIA 51 STERILE CORNEAS LENTICULAR EXTRACTION AND ADDITION Discovering the potential of a new frontier in refractive surgery. 32 CATARACT & REFRACTIVE SURGERY TODAY EUROPE | FEBRUARY 2021 enticular surgery is gaining thickness of the corneal lenticules, potential for allografts to be used momentum, and rightfully which increased the risk of epithelial in a variety of refractive treatments, so. More than 3.5 million ingrowth and poor reepithelialization. including for hyperopia, presbyopia, SMILE procedures have More recently, hypoallergenic and keratoconus. Lastly, allograft been performed worldwide, synthetic corneal implants have lenticules are acellular, and therefore and other lenticule extraction been used for refractive purposes. sterile tissue donor immunogenicity procedures are being introduced These synthetic implants are made will be reduced. and studied. It is likely only a matter of biocompatible materials, but their Lof time before these procedures biocompatibility is not equivalent to CONCLUSION are available worldwide. On top that of allogenic implants currently I believe that what we are of the advances being made in in use and being studied for certain performing today is modern, modified lenticule extraction surgery, allogenic conditions. epikeratophakia surgery. Using the lenticules are now used in certain tools and techniques developed over regions of the world to treat some EPIKERATOPHAKIA REIMAGINED the past several years, corneal tissue of the hardest refractive errors to The availability of precise can now be packaged and stored correct—emmetropic presbyopia laser-shaping systems and sterile at ambient conditions (15–30 ºC and hyperopia—and allogenic ring corneas are key factors that make and 30%–80% relative humidity) for segments are being studied for the use of allogenic implants possible at least 2 years, helping to expand the treatment of keratoconus. The today. The goal of this lenticular indications and areas of reach. future for all of these applications surgery procedure is to enhance the Before he died, my mentor Joseph looks bright. visual performance with a material Colin, MD, always told me, “The The articles in this series highlight that is 100% biocompatible and cornea cannot accept a foreign the recent advances in lenticular precisely shaped for an individual’s body.” I believe that he was right, and extraction and addition and postulate personal needs. today we have enough experience to the impact of these procedures as In addition to complete understand the interaction between catalysts for the growth of refractive biocompatibility, the use of biosynthetic corneal materials surgery. In my guest editorial, I allogenic implants is advantageous and the cornea. Corneal lenticular focus on the potential of modified because there is no tissue removed surgery may not be an alternative epikeratophakia. from the eye and because the effects to all types of corneal laser surgery, of the surgery can be reversed but it may represent a unique, safe, THE HISTORY OF EPIKERATOPHAKIA by removing the implant. This is reversible, adjustable, exchangeable, In 1949, José Ignacio Barraquer an important consideration for and noninvasive solution for the laid the groundwork for the use of patients and surgeons. treatment of emmetropic presbyopia, natural corneal tissue to change Compared to initial attempts keratoconus, hyperopia, post-LASIK the refractive properties of the eye.1 at epikeratophakia, the use of emmetropic presbyopia, and During epikeratophakia, corneal tissue state-of-the-art excimer lasers to eyes with thin corneas. n is lathed to an attempted specific shape allogenic implants in modern 1. Barraquer JI. Modification of refraction by means of intracorneal inclusions. dioptric power and sutured on top of epikeratophakia-type procedures Int Ophthalmol Clin. 1966;6(1):53-78. the recipient’s cornea. In its earliest mitigates the problems related iterations, this technique was used for to power and the induction of aphakia or hyperopia. Early attempts astigmatism. Current shaping with this approach, however, had techniques also allow the creation of unpredictable results due to problems allografts that are significantly thinner with cryolathing the preserved than what was used in Barraquer’s corneal tissue; difficulty preparing the early attempts with epikeratophakia lenticules; structural damage to the procedures. Further, research and tissue during the required freezing development of technologies used and lathing process; and the required to shape the allografts influence the AYLIN KILIÇ, MD | GUEST MEDICAL EDITOR FEBRUARY 2021 | CATARACT & REFRACTIVE SURGERY TODAY EUROPE 33.