Dr. Hoyos’s Step by Step Lamellar Corneal Graft Jairo E Hoyos, Eduardo Arenas
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1Dr. Hoyos's Step by Step Lamellar Corneal Graft2
3Dr. Hoyos's Step by Step Lamellar Corneal Graft
Editors Eduardo Arenas MD, DOMS, FACS Fundación Santa Fe, Clínica Shaio Professor National University and Javeriana University Bogotá, Colombia Jairo E Hoyos MD, PhD Instituto Oftalmológico Hoyos KM Study Group President Sabadell, Barcelona, Spain Foreword Frank M Polack
4Published by
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Dr. Hoyos's Step by Step Lamellar Corneal Graft
© 2006, Eduardo Arenas, Jairo E Hoyos
All rights reserved. No part of this publication should be reproduced, stored in a retrieval system, or transmitted in any form or by any means: electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of the editors and the publisher.
First Edition: 2006
9788180617768
Typeset at JPBMP typesetting unit
Printed at Gopsons Paper Ltd, Noida
5
This book is dedicated to all
ophthalmologists who devote their
work in trying to restore the
transparency and regularity of
the cornea.
6
7Contributors
11Foreword
For everything there is a season
—Ecclesiastes
The time for lamellar keratoplasty has finally arrived; an old surgical procedure has always been outshined by the more glamorous technique of penetrating keratoplasty. Lamellar keratoplasty (LK) has fallen in and out of favor, being regarded as a tectonic procedure or as a graft for superficial corneal scars.
The editors of this book, Arenas and Hoyos, are experienced corneal surgeons, well known writers and editors of scientific articles. They have seen the need for this publication and have undertaken the formidable task of putting together actual information about a variety of techniques and indications for partial lamellar keratoplasty, some so revolutionary that they are still unknown in some medical centers. To this effect, they have obtained the collaboration of a group of internationally known corneal surgeons to write specialized chapters. I am grateful to the editors for asking me to write this Foreword.
The classical lamellar KP was always considered a difficult technique that was performed by a few surgeons and avoided by most others. Its great advantage was the 12fact that satisfactory results could be obtained with old corneal tissue or with corneas stored in glycerin, alcohol or frozen; but this unusual characteristic could not replace the need for living tissue demanded in cases of corneal edema. Because of the scarcity of fresh donor corneas, the lamellar keratoplasty technique has been used mostly in countries where eye banks were nonexistent and the access to fresh tissue was almost impossible. In some countries even heterologous lamellar grafts have been performed routinely.
Through the years I have seen the development of ingenious instruments and techniques to facilitate the LK procedure. Dr. Ramon Castroviejo, a strong proponent of lamellar grafts, developed an electric microkeratome that made cuts of various thickness from a donor globe as well as the excision of thin layers from the recipient's cornea. However, the most refined and sophisticated technique for lamellar keratoplasty was ‘keratomileusis’, invented by Dr. Jose I Barraquer, which opened the door for today's refractive surgery. Barraquer's restless mind was constantly thinking of different ways to improve this method and develop others. On one occasion when talking to him about surgical instrumentation and design of microscopes, I asked him if he was always thinking about his instruments and how to make new ones. He replied that in effect he was always thinking about his work and that it was good to keep the mind busy with your own problems all the time in order to find new ways to solve them. Similarly, the advances in LK are due to the persistent interest and dedication by scientific minds following the example of Jose I Barraquer.13
It is the desire to learn, explore and discover which brings advances in science and technology. The desire to know is innate in us, wrote the sixteenth century philosopher Benedict de Spinoza, but not everybody uses it. We, the teachers of the science of medicine, as well as the editors of scientific books, have a duty not only to teach but also to facilitate and spread knowledge. However, because of our experience we also have the duty to help or guide the young investigator, although at times we must temper his enthusiasm and remind him that most discoveries are not new at all. When I was a corneal fellow, while doing some experiments that required freezing corneas of living animals, I realized that the intraocular pressure decreased in these eyes. This was caused by damage to the ciliary body. I reported this discovery to my chief Dr. George Smelser. Although he was very interested and had not heard of this effect, he told me that I should go to the library and do an extensive research about this finding, because it was almost certain that somebody had already seen it. And it was indeed; it was a procedure described by Bietti in Rome in 1935 for glaucoma, using fragments of dry ice. The technique had been abandoned, but following my report with Dr. Andy de Roeth the operation was revived as cyclo-cryotherapy because a cryoinstrument for retinal surgery was already available.
The numerous papers included in this book illustrate the multiple techniques and indications for this type of surgery at the present time. Some procedures were not 14even dreamed of a few years back, except in the minds of a few that were ahead of their time. I am thinking of physiological experiments done in the fifties by Cogan and Kinsey and also by Dohlman, Mishima, and Maurice, where an impermeable intralamellar membrane controlled corneal hydration and explained the mostly unknown function of endothelial cells in corneal transparency. Dr. David Maurice then suggested that endothelial cells could be grown in a membrane and transplanted. But it was not until recently that the most interesting procedure, which was a possibility some years ago, is now a reality: it is the transplantation of the endothelial layer in the operation known as Posterior lamellar keratoplasty (PLK) (or Deep lamellar endothelial keratoplasty DLEK/or Descemet's stripping automated keratoplasty DSAEK). It appears, therefore, that many ideas reach the right time for implementation when they converge with the development of new technology or instruments. This is what happened when a viscoelastic discovered by Endré Balach to replace the vitreous, was found to prevent damage to the corneal endothelium. The viscoelastic Healon has been an integral part in the advance of penetrating keratoplasty results.
The origin of posterior lamellar keratoplasty can be traced back to a report of Jose I Barraquer, during the First Cornea Congress in 19651, when he described a technique to graft the endothelial layer in edematous corneas.
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The somewhat complicated technique was used also by Dr. Raul Rodriguez Barrios2 and presented at the same meeting. The purpose of the operation was to reduce astigmatism and diminish the risk of rejection. I learned the technique from Rodriguez at that time3 and did a series of experimental grafts that showed me the problems of the procedure, the degree of endothelial damage caused during the procedure (before Healon was invented), the process of healing and the possible absence of rejection of the grafted layer. In spite of the good results and the possibility of new instruments being manufactured, the time was not ripe for this procedure. It was tedious, a significant loss of endothelial cells occurred and the technique of full thickness penetrating keratoplasty was producing better results everyday. We are all benefiting now from the newest of the lamellar keratoplasties.
The table of contents shows what pathologists call “sequence of events” in this case, how a procedure has been gradually changed and perfected through the years with the help of new ideas and technical innovation.
Frank M Polack
MD
Founding editor of the medical journal “Cornea”
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17Preface
Keratoplasty in both its forms, lamellar and penetrating, is the surgical technique used to restore the cornea's transparency and regularity. Possibly, bullous keratopathy has been the indication par excellence for a keratoplasty due to a critical level of endothelial cells in this condition, insufficient to keep the cornea dehydrated and therefore transparent. In other cases, we are confronted with a corneal opacity at the level of the Bowman's membrane or in the surface or deep stroma owing to an anterior dystrophy, or as the consequence of corneal infection or trauma. In yet further cases, we have to deal with a degenerated corneal structure such as occurs in keratoconus or pellucid marginal degeneration. When performing a penetrating keratoplasty, the full thickness of the cornea is replaced. However, given that sometimes only part of this thickness is affected, several new lamellar keratoplasty techniques have gradually appeared on the scene.
Owing to the poor initial results of these lamellar corneal grafts, penetrating keratoplasty has been the most popular technique over the past few decades. The recent appearance of several newly developed lamellar procedures has, nevertheless, rekindled our interest in this procedure to the extent that today lamellar keratoplasty 18is the method of choice for treating a corneal problem restricted to one or some of its layers.
Thus, we now have techniques capable of excising the surface layers of the cornea with an opacity or irregularity and replacing the tissue removed with a similar amount of transparent donor corneal tissue. We can thus avoid transplanting the donor corneal endothelium, which is responsible for most corneal rejection episodes.
Other lamellar techniques are designed to only replace the layer of endothelial cells and thus restore the cornea's transparency when there is a functional endothelial defect. Hence, by not having to touch the anterior, healthy layers of the cornea, we can avoid causing refractive changes that could affect the final visual acuity of the patient.
These last decades have seen an increase in cases requiring a corneal transplant as a consequence of the complications produced by an ever-increasing number of corneal refractive and intraocular procedures. We should not forget that a keratoplasty can fail when the graft becomes opaque due to initial failure of the procedure, or when rejection or graft vascularization occur later on. In addition, often the transplanted cornea preserves its transparency yet the patient's vision is not restored due to high postoperative refractive errors. Although we still have a long way to go with lamellar techniques, the path is now clear for new developments that will enable us to restore the anatomy and visual function of the cornea much 19more rapidly, while minimizing the complications of penetrating techniques in the short-and long-term.
We hope that this review of the most recent lamellar keratoplasty techniques will be informative for the anterior segment surgeon.
Eduardo Arenas
Jairo E Hoyos