Ординатура / Офтальмология / Английские материалы / Corneal Endothelial Transplant (DSAEK, DMEK & DLEK)_John_2010

Foreword ..........................................

At the current moment, keratoplasty is undergoing an incredible paradigm shift in surgical technique. A field dominated by Penetrating Keratoplasty, where advances such as improved trephination systems, corneal preservation media, and suturing techniques while meaningful, have clearly been only incremental, is simultaneously going lamellar, minimally invasive, and sutureless. Lead by the extraordinary success of Deep Lamellar Endothelial Keratoplasty (DLEK), the concept of transplanting only the corneal layer which is diseased or damaged and needs replacing is gaining significant traction amongst corneal surgeons worldwide. Replacing the corneal endothelium only in a patient with Pseudophakic/ Aphakic Bullous Keratoplasty or Fuchs’ Dystrophy rather than replacing the entire cornea with a full-thickness

Penetrating Keratoplasty has gone from the research interest of a few pioneering surgeons to mainstream in an amazingly short time. In addition to DLEK, we now have Descemet’s Stripping Automated Endothelial Keratoplasty (DSAEK) competing for our attention.

At the same time, the Intralase femtosecond laser is being harnessed in an attempt to make Penetrating Keratoplasty more precise with the promise of more predictable refractive outcomes. It is truly not only an exciting time for the corneal surgeon, but also a demanding one requiring the rapid assimilation of new knowledge as well as the development of new surgical skills.

Fortunately, Thomas John MD has produced for us a timely and outstanding educational offering in his new book “Corneal Endothelial Transplant (DSAEK, DMEK & DLEK)”. This very comprehensive book includes the history of lamellar transplantation; an in-depth discussion of the basic science of corneal structure, physiology, biomechanics and pathology; a primer on advanced corneal imaging; a review of the surgical instrumentation required; and of utmost importance, detailed instruction by the leaders in the field on the current best practices of surgical technique and complications management. A final section provides an enticing glimpse to the future.

This book is complete enough to serve the corneal fellow well and advanced enough for even the most accomplished corneal surgeons to include in their personal library. Thank you, Dr John and colleagues, for providing we corneal surgeons with such an extraordinary educational resource.

Richard L Lindstrom MD

Founder and Attending Surgeon

Minnesota Eye Consultants

Adjunct Professor Emeritus

Department of Ophthalmology, University of Minnesota

Associate Director, Minnesota Lions Eye Bank, USA

Preface ..............................................

This book entitled, Corneal Endothelial Transplant (DSAEK, DMEK & DLEK) is dedicated to the new way of performing corneal transplantation namely, without the use of corneal sutures and an absence of a full-thickness corneal wound. Such a move towards advanced corneal replacement surgery eliminates the induction of much disliked corneal astigmatism. Such a textbook provides the corneal surgeon with a variety of surgical techniques and instrumentation that will be a useful surgical resource for posterior lamellar keratoplasty procedures.

For several decades, full-thickness penetrating keratoplasty (PKP) has dominated the field of corneal transplantation and has remained as the gold standard for corneal replacement surgery. However, the time has come when improved lamellar corneal techniques has re-appeared in the global horizon as a rapidly popular surgical technique and is beginning to challenge and possibly replace PKP as the gold standard in the times ahead. The editor has previously introduced a new term namely, Selective Tissue Corneal Transplantation (STCT) which may become the procedure of choice in many corneal disease processes. Why remove the whole cornea when the pathology may be limited regionally to either the front, middle or back part of the cornea? I have previously edited two books that covered both anterior and posterior lamellar keratoplasty, entitled, Surgical Techniques in Anterior and Posterior Lamellar Corneal Surgery, and Step by Step Anterior and Posterior Lamellar Keratoplasty. Due to the increasing popularity of posterior lamellar keratoplasty among corneal surgeons all over the world and the rapidly changing and evolving sutureless corneal transplantation techniques, this book collectively provides the reader with a wide assortment of surgical techniques from world leaders in the field of sutureless corneal transplantation as we know it today (at the time of writing this book). This book has numerous color photographs to assist in fully understanding the various surgical techniques described in the text. The editor and contributors have made it their priority to present the surgical techniques in a way that is easily understood by the readers of this textbook.

This surgical text consists of 11 sections and 39 chapters. In Section 1, new areas of interest such as corneal hysteresis and biomechanical properties of the normal cornea are described. In addition, corneal physiology is covered. Also described in this section is the most important layer of the cornea that is responsible for corneal clarity, namely, corneal endothelium, both in health and in the disease state.

In Section 2, new ways of imaging the human cornea are described. In vivo, real-time imaging of the cornea provides useful information both before and after surgery. This includes, Optical Coherence Tomography (OCT), Very High Frequency (VHF) ultrasound and confocal microscopy. The area of imaging covers both the cornea and the anterior segment.

Section 3 presents the new generation operating microscope. This futuristic microscope provides a 3D perspective that is novel and may change the way we perform ophthalmic surgery in the future. Also included in this section is the use of intraoperative surgical slit-lamp microscope to assist in lamellar corneal surgery, namely, both anterior and posterior lamellar keratoplasty.

The next section deals with the various new and useful surgical tools for the corneal surgeon to assist in performing sutureless corneal transplantation. Much like a paint brush is to an artist, so is the proper surgical instrument to the surgeon that will help in consistently performing high quality surgical work. It is not enough to have the best microscope and operating room setup. Equally or more important are the appropriate surgical instruments. This section describes the various surgical instruments that are commercially available to assist in performing posterior lamellar keratoplasty.

Section 5 deals with an essential and important part of the instrumentation to perform posterior lamellar keratoplasty, namely, the artificial anterior chamber. A good understanding of the various types of artificial anterior chambers that are available will help the surgeon doing posterior lamellar keratoplasty. Both non-disposable and disposable types of artificial anterior chambers are described in this section of the book. This is especially important when the surgeon prefers to cut his or her own donor corneal tissue in the operating room rather than to use the corneal tissue that are pre-cut by eye bank technicians and supplied by the various eye banks in the United States for an additional fee. Newly introduced in the United States is a reimbursement code for surgeons preparing and cutting their own donor corneal disk for DSAEK, in addition to the DSAEK code for the DSAEK surgery.

Acknowledgments ...........................

I acknowledge all those who contributed to this book on “Corneal Endothelial Transplant,” by taking time from their busy schedules to write their chapter(s). A collective contribution and passion for their surgical pursuits makes this compilation valuable for readers all over the world.

I wish to acknowledge all my teachers in the Cornea Service, Massachusetts Eye and Ear Infirmary (MEEI), Harvard Medical School, Boston, MA, USA, from whom I have learnt immensely both in the clinical and research aspects of “Cornea”. I am thankful to Drs Kenneth R Kenyon, Claes H Dohlman, C Stephen Foster, Roger F Steinert, Deberoah P Langston, Mark B Abelson, Michael D Wagoner, Jeffrey P Gilbard, Arthur S Boruchoff, and Ann M Bajart for all their dedication and effort in teaching surgical and medical skills relating to cornea and external diseases while I was a 2-year Clinical Cornea Fellow at Harvard. I wish to thank Dr Kenyon, under whose expert guidance I did my research work both at the Schepens Eye Research Institute and at the Massachusetts Institute of Technology (MIT), in Boston. I am fortunate to have worked with my colleagues, cornea fellows and residents at MEEI during my fellowship years, to name a few, Drs Mitchell C Gilbert, Eduardo C Alfonso, Kazuo Tsubota, Scheffer CG Tseng, Dimitri T Azar, John R Wittpenn, and Oliver D Schein.

Special thanks to Drs James V Aquavella and Gullapalli N Rao for what they taught me in corneal surgery including epikeratoplasty, refractive surgical procedures, and keratoprosthesis.

I am thankful to all my teachers in my formative years during my ophthalmology residency at the University of Pennsylvania. Although, not an all inclusive list, special thanks to Drs Ralph C Eagle, Jr, Myron Yanoff, John H Rockey, Irving M Raber, Alexander J Brucker, David M Kozart, William C Frayer, Harold Scheie, and Madeleine Q Ewing. I am especially thankful to Ralph C Eagle, Jr, MD, for all his support and professional inspiration, and for teaching me the various pathological basis of disease processes as it relates to the eye. I thank Myron Yanoff for accepting me into the ophthalmology residency program at the University of Pennsylvania.

Teachers are one of the greatest assets of any society. I thank all my teachers from kindergarten to completion of my formal education both in the medical and pre-medical years. Without these teachers, I will be lacking in knowledge and I am indebted to each and every one of my teachers.

I wish to acknowledge my wife, Annita, and the kids, Michelle, Andrea and Olivia for putting up with my late night academic work and for all their understanding and loving support.

Thanks to Laura Phelps for the excellent medical illustrations in this book.

To my office staff, for their patience and understanding.

To all my patients, from whom I continue to learn everyday. Learning is a continuous and dynamic process that stimulates the mind and makes ophthalmology an even more interesting and challenging field in our life’s journey.

Introduction.....................................

Sutures have been a necessary evil in most forms of corneal surgery. Sutures have historically been necessary to obtain a secure incision during the healing phase. The introduction of sutures in cataract surgery, utilizing large re-usable needles that the surgeon had to thread, in a manner like a tailor, represented a major breakthrough in rehabilitation after cataract surgery. As the needles and suture material became smaller and the number of possible sutures in a single incision increased, the patient rehabilitation time improved dramatically while the complication rate fell. No longer were cataract patients restricted to bed rest with their heads stabilized by sand bags, awaiting for healing of a limbal incision secured only by an overlying conjunctival flap. The problem with sutures in cataract surgery, of course, was the impossibility

of precise control of the suture tension and placement. After prolonged healing, typically lasting several months, the patient might have high amounts of astigmatism representing either excessively tight or excessively loose sutures. These issues are now largely a historical footnote, as cataract surgery has come full circle. The drive for smaller incisions in cataract surgery allowed the creation of a self-sealing “valve” incision that, because of its inherent water tightness and structural stability, permits surgeons to use no sutures in many cases. In coming full circle and returning to sutureless cataract surgery, the evolution of the “valve” style incision represented a re-learning of the incision shape that helped cataract surgeons with sutureless incisions in the early 20th century, because the Graefe knife incisions of that era also created the same valve effect, unfortunately limited by the extreme width of the incision necessary to perform the whole lens surgery of that era.

The lessons of sutures in cataract surgery apply even more to corneal surgery. In corneal transplantation, until recently, sutures have been mandatory to align and stabilize the junction of the donor and the recipient cornea. Because the cornea is slow to heal, those sutures must be retained much longer than in cataract surgery. In almost all cases, the sutures are also considerably closer to the optical center and the limbus. This proximity dramatically increases the negative impact of suture tension.

Despite decades of improvement in suture materials, needles, and ingenious variations in suturing technique and suture patterns, the problem of distortion and slow healing of corneal incisions has remained as a powerful impediment to high quality vision after corneal transplantation. Indeed, another of the ironies in this story of sutures in ophthalmology came with a shift from silk sutures to fine nylon sutures for corneal transplantation. Silk sutures caused intense inflammation, vascularization, and higher rejection rates as well as patient discomfort. However, if the transplant survived, the patient benefited by the stimulation of more rapid incision healing and full suture removal much earlier than is possible with nylon sutures. The use of non-inflammatory material, therefore, caused a further shift in the direction of prolonged dependency on sutures and vulnerability to the negative impact of those sutures in corneal surgery.

This outstanding text, conceived and edited by Thomas John, MD thoroughly explores the dramatic shift under way toward corneal transplantation without corneal sutures. The text thoroughly develops the background technologies that are the foundation of lamellar endothelial transplantation.

Current endothelial transplant surgery typically still involves a few limbal sutures, but the future is clearly in the direction of transplantation of endothelial cells alone. That will complete the transformation to a completely sutureless corneal transplantation.

Roger F SteinertMD

Chair of Ophthalmology Director of the Gavin Herbert Eye Institute Professor of Ophthalmology and Biomedical Engineering Department of Ophthalmology University of California, Irvine, CA, USA