AlphaCor™ cases : comparative outcomes

C.R. Hicks, Geoffrey Crawford, D.T. Tan, G.R. Snibson, G.L. Sutton, N. Downie, T.D. Gondhowiardjo, D.S.C. Lam, L. Werner, D. Apple, Ian Constable

Research output: Contribution to journalArticle

45 Citations (Scopus)

Abstract

Purpose: To describe clinical outcomes after a novel type of corneal surgery, implantation of an artificial cornea, AlphaCor™, and to evaluate outcomes in comparison with alternative keratoprostheses and high-risk grafts.Methods: Case reports and data from a noncontrolled clinical trial and a literature review.Results: The probability of AlphaCor retention to 1 year is 80%. Postoperative best corrected visual acuity ranges from Perception Light to 20/30. The most significant complications are stromal melts and optic depositions, for both of which the main risk factors have been identified. Complications can be managed without loss of the eye.Conclusion: Results from the clinical trial period have helped to determine the indications and risk factors for AlphaCor surgery and to refine surgical techniques. Continued monitoring of outcomes as the series increases will allow a more accurate determination of comparative outcomes. The series provides preliminary evidence that AlphaCor may have a lower incidence of complications than traditional keratoprostheses and may prove to be preferable to a donor graft in high-risk cases.Replacement of an opaque cornea using a synthetic cornea, AlphaCor™, in cases where a donor graft is deemed highly likely to fail is a relatively new technique that has been under clinical investigation since 1998. With regulatory approvals, use of this device is likely to increase. AlphaCor outcome data have been reported previously, 1-3 but we now aim to give an overview of outcomes, illustrated with case histories, in comparison with outcomes of alternative treatments.The investigation commenced with a protocol provided as part of a Clinical Investigators' Brochure. This document has undergone 2 revisions during the investigation to reflect changes to protocol determined by interim findings. In summary, patients in this report enrolled before November 2000 were under the original protocol, which included routine prescription of topical 1% medroxyprogesterone (MPG) as a postoperative medication for the first postoperative year, as a putative anticollagenase agent. Revision 1 (November 2000) of the protocol stopped use of MPG for subsequent cases at the request of regulatory authorities because it is not approved for this indication. A further revision of the protocol (Revision 2, November 2001) formally excluded further recruitment of patients with a history of ocular herpes simplex virus (HSV) in recognition of an increased risk of melting in these patients and also warned specifically against contact lens wear and smoking, all these factors having become apparent in the investigation up to that date.Inclusion criteria, the device, surgical technique, and protocol management have been described previously. 1-3 The study was conducted in conformance with international ethical requirements, and all patients gave informed consent. Briefly, the device is a hydrogel core-and-skirt keratoprosthesis (KPro) that is implanted (stage I) within the corneal plane in a lamellar pocket, followed by opening of tissues anterior to the optic after 12 weeks (stage II). Routine postoperative medications (protocol revisions 1 and 2) include topical steroid and antibiotic for the first 4 weeks after stage I and very briefly after stage II, with the only long-term medication routinely used in the long term being topical 1% tetracycline ointment (Latycin™, Boucher & Muir Pty Ltd, Crows Nest, Australia, in most investigational centers). Additional medications, such as for glaucoma or inflammation, were used at the surgeon's discretion where required and recorded in detail. Data were recorded for every patient at every postoperative visit during the study, and no patients have been lost to follow-up. Two patients died of unrelated causes during the course of the study. Data in this report are current to the end of January 2003.Explanted devices were processed for examination at the Center for Research on Ocular Therapeutics and Biodevices, including gross (macroscopic) analysis, with pictures taken using a camera (Nikon N905 AF, Nikon Corporation, Tokyo, Japan) fitted to an operating microscope (Leica/Wild MZ-8 Zoom Stereomicroscope, Vashaw Scientific, Inc, Norcross, GA). The unstained devices were then evaluated microscopically and photographed under a light microscope (Olympus, Optical Co. Ltd, Japan). Each prosthesis was then divided into 2 halves. One was dehydrated and embedded in paraffin. Sagittal sections were performed and stained using hematoxylin and eosin (H&E), Periodic acid-Schiff (PAS), Masson's trichrome, von Kossa's method, and alizarin red/light green (for calcium), and Grocott's methenamine-silver nitrate (GMS; for fungus). The second half of explants was used for scanning electron microscopic (SEM) examination.
Original languageEnglish
Pages (from-to)583-590
JournalCornea
Volume22
Issue number7
DOIs
Publication statusPublished - 2003

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