Ординатура / Офтальмология / Английские материалы / Corneal Endothelial Transplant (DSAEK, DMEK & DLEK)_John_2010
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Perspective .......................................
Seems like just a year ago that we witnessed publication of Thomas John’s definitive magnum opus of lamellar keratoplasty, “Surgical Techniques in Anterior and Posterior Lamellar Corneal Surgery” (Jaypee Brothers, New Delhi, 2006). Can it really be time for yet another multifaceted, multi-authored work on posterior lamellar keratoplasty ??
Answer: Absolutely !!
The Back to the Future of century old anterior lamellar keratoplasty techniques have now been extended and adapted for posterior corneal application plus technologically enhanced by current imaging and surgical instrumentation. This Paradigm Shift to Targeted Tissue-
Specific Keratoplasty is clearly the greatest advance in corneal surgery to occur within the last half century (Top 10 Ophthalmic Innovations of the Past 25 Years, Ocular Surgery News, Dec. 2007). Such rapid developments of the past decade, thanks to Dr. John and several of the nearly 50 international authors contributing to the current treatise, have propelled Endothelial Keratoplasty to have become the nearly standard approach for the surgical management of corneal endothelial disease.
Little more than a year ago has passed since my own pilgrimage to Chicago (?or was it Lourdes or perhaps Mecca…?) to witness and learn from the Master K-Plaster, Tom John, himself. Thusly converted, I can now personally attest to the Miracle of Posterior Lamellar Keratoplasty. True, this surgery and its variations requires mastery of new surgical skills as well as problem solving and complication management, as does any novel operative technique. Yet having witnessed the surgery and its results (including the increasingly long-term published series, as are also included herein), the Bottom Line is all too obvious: Once you go DSEK, you never go back !
And so it is that Dr. John and friends rapidly push forward and relentlessly expand the frontiers through their current approaches to the state of the sutureless keratoplasty art. Including sections devoted to corneal basic science, tissue imaging, surgical instrumentation, basic themes plus multiple variations of endokeratoplasty technique, and future directions, this opus is a definitive work of equally magnum magnitude which should convince even more conservative corneal surgeons that the Back to the Future of lamellar keratoplasty is unquestionably now. Finally, I must also express my personal and professional appreciation to Thomas for both the honor of including me among his illustrious cast of coauthors but especially for the Epiphany of helping me to Perceive the Light.
Kenneth R Kenyon MD
Founder, Cornea Consultants International
Boston, MA, USA & Munich, Germany
Associate Clinical Professor of Ophthalmology
Harvard Medical School, Boston, MA, USA
Senior Scientist, Schepens Eye Research Institute
Boston, MA, USA
Contents ...........................................
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Section 1: Cornea |
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1. |
Corneal Hysteresis and Biomechanics of the Normal Cornea ...................................................................................... |
3 |
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Mujtaba A Qazi, Jay S Pepose (USA) |
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2. |
Corneal Physiology ............................................................................................................................................................. |
13 |
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Wisam A Shihadeh (Jordan), Almamoun Abdelkader (Egypt), Herbert E Kaufman (USA) |
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3. |
Corneal Endothelium in Health and Disease ................................................................................................................ |
23 |
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Pedram Hamrah, Eric C Amesbury, Richard A Eiferman (USA) |
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Section 2: Corneal Imaging |
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4. |
Optical Coherence Tomography (OCT) of the Anterior Segment ............................................................................... |
39 |
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George Baikoff (France) |
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5. |
Optical Coherence Tomography in Corneal Implant Surgery ..................................................................................... |
47 |
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Roger F Steinert (USA) |
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6. |
Use of Optical Coherence Tomography (OCT) in Descemet’s Stripping with Endothelial |
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Keratoplasty (DSEK) and Descemet’s Stripping Automated Endothelial Keratoplasty (DSAEK) ....................... |
53 |
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Leejee H Suh, William W Culbertson (USA) |
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7. |
Imaging of the Cornea and Anterior Segment with High-Frequency Ultrasound ................................................... |
61 |
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Ronald H Silverman, Monica Patel, Omer Gal, Harriet O Lloyd (USA) |
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D Dan Z Reinstein (UK), D Jackson Coleman (USA) |
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8. |
Confocal Microscopy of the Cornea ...................................................................................................................................................... |
71 |
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Jasmeet S Dhaliwal (USA), Auguste G-Y Chiou (Switzerland), Stephen C Kaufman (USA) |
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Section 3: Next Generation Operating Microscope |
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9. |
Next Generation Operating Microscope: 3D Digital Microscope and Microsurgical Workstation ....................... |
85 |
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Ramagopal Rao, David Miller (USA) |
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10. |
Role of Surgical Slit-lamp in Endothelial Transplantation and Anterior Segment Surgery ................................... |
95 |
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Thomas John (USA) |
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Section 4: Surgical Instruments |
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11. |
New/Useful Surgical Instruments in DSAEK .............................................................................................................. |
107 |
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Thomas John (USA) |
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Section 5: Artificial Anterior Chambers |
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12. Artificial Anterior Chambers .......................................................................................................................................... |
123 |
Thomas John (USA) |
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xxiv |
Corneal Endothelial Transplant |
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Section 6: Classification of Lamellar Corneal Surgery |
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13. |
Definition, Terminology and Classification of Lamellar Corneal Surgery.............................................................. |
133 |
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Thomas John (USA), Enrique S Malbran (Argentina) |
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Section 7: History |
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14. |
History of Lamellar and Penetrating Keratoplasty ...................................................................................................... |
143 |
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Thomas John (USA), Luiz F Regis-Pacheco (Brazil), José G Pecego (Brazil), Mark A Terry (USA) |
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Section 8: Deep Lamellar Endothelial Keratoplasty (DLEK) |
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15. |
Deep Lamellar Endothelial Keratoplasty (DLEK): Large Incision Technique ....................................................... |
157 |
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Mark A Terry, Paula J Ousley (USA) |
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16. |
Deep Lamellar Endothelial Keratoplasty (DLEK): A Procedure for Special |
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Cases of Endothelial Dysfunction .................................................................................................................................. |
171 |
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Mark A Terry (USA) |
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17. |
Deep Lamellar Endothelial Keratoplasty: Small Incision Technique |
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Combined with Phacoemulsification and Posterior Chamber IOL .......................................................................... |
183 |
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Mark A Terry (USA) |
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18. |
Deep Lamellar Endothelial Keratoplasty (DLEK) Combined with Scleral-fixated Posterior |
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Chamber Intraocular Lens Implantation ...................................................................................................................... |
201 |
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Ashraf Amayem, Magdi Helal (Saudi Arabia) |
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Section 9: Descemet’s Stripping Automated |
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Endothelial Keratoplasty (DSAEK) |
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19. |
Eye Banking and Donor Corneal Tissue Preparation in DSAEK ............................................................................. |
217 |
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Anastasios John Kanellopoulos (Greece) |
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20. |
Endothelial Keratoplasty: A Step by Step Guide to DSEK and DSAEK Surgery ................................................... |
225 |
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Mark A Terry (USA) |
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21. |
Improved DSAEK Surgery for Enhanced Endothelial Survival................................................................................ |
237 |
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Massimo Busin, Vincenzo Scorcia (Italy) |
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22. |
Endothelial Keratoplasty: Visual and Refractive Outcomes...................................................................................... |
245 |
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Marianne O Price, Francis W Price (USA) |
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23. |
DSAEK Simplified Surgical Technique ....................................................................................................................... |
253 |
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Thomas John (USA) |
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24. |
Surgical Technique for Descemet Stripping Automated Endothelial Keratoplasty (DSAEK) ............................ |
281 |
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Mark S Gorovoy (USA) |
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25. |
Descemet’s Stripping Endothelial Keratoplasty (DSEK), Through a 3 mm Incision using the |
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Tri-fold Technique ........................................................................................................................................................... |
289 |
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Keith A Walter, Marshall E Tyler (USA) |
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26. |
Femtosecond Laser (Intralase®) – Descemet’s Stripping Endothelial Keratoplasty (Femto-DSEK): |
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Initial Studies of Surgical Technique in Human Eyes ............................................................................................... |
293 |
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Ciro Tamburrelli, Agostino Salvatore Vaiano, Emilio Balestrazzi (Italy) |
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Contents |
xxv |
27. |
Techniques to Facilitate Disk Adherence to Recipient Cornea in DSAEK ............................................................. |
303 |
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Thomas John (USA) |
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28. |
Complication Management in DSAEK ......................................................................................................................... |
311 |
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Thomas John (USA) |
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29. |
Unanswered Questions in DSAEK ................................................................................................................................ |
327 |
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Thomas John (USA) |
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30. |
Use of Eye Bank Pre-cut Donor Tissue in DSAEK ...................................................................................................... |
331 |
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Anthony Kuo, Terry Kim (USA) |
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Seciton 10: DLEK Versus DSAEK |
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31. |
Comparison of Wound Architecture in DLEK Versus DSAEK ................................................................................. |
343 |
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Thomas John (USA) |
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32. |
Use of Dyes in DSAEK and DLEK ................................................................................................................................. |
349 |
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Thomas John (USA) |
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33. |
Comparative Visual Recovery in DSAEK, DLEK and PKP ........................................................................................ |
361 |
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Mark S Gorovoy (USA) |
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Section 11: DMEK and Future Directions in Posterior |
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Lamellar Keratoplasty |
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34. |
Posterior Lamellar Keratoplasty Using Tissue Adhesive ........................................................................................... |
367 |
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Juan M Castro-Combs, Naima B Jacobs-El, Ashley Behrens (USA) |
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35. |
Novel Approach for Corneal Endothelial Cell Transplantation using Descemet Membrane as a Carrier ........ |
377 |
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Naima B Jacobs-El, Juan M Castro-Combs, Ashley Behrens (USA) |
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36. |
True Endothelial Cell (TEnCell) Transplantation........................................................................................................ |
389 |
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Panagiotis Georgoudis, Michael J Tappin (UK) |
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37. |
Descemet Membrane Endothelial Keratoplasty (DMEK) ......................................................................................... |
399 |
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Massimo Busin (Italy) |
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38. |
Corneal Endothelial Reconstruction with a Bioengineered Cell Sheet .................................................................... |
405 |
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Jui-Yang Lai, Ging-Ho Hsiue (China) |
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39. |
Future of Posterior Lamellar Keratoplasty .................................................................................................................... |
421 |
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Thomas John, Kenneth R Kenyon (USA) |
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Index ..................................................................................................................................................................................... |
425 |
Mujtaba A Qazi, Jay S Pepose
Corneal Hysteresis and
Biomechanics of the
Normal Cornea
1
4 |
Corneal Endothelial Transplant |
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Introduction
The structural characteristics of the cornea facilitate its essential functions, specifically to serve as both a transparent barrier and the predominant refractive element of the eye. Given the integral relationship between form and visual function, the biological and mechanical responses of the cornea to surgical interventions impact its optical performance. While major advances have occurred in the refinement and standardization of corneal surgical techniques, our ability to predict individual biological responses to surgery remains limited and can influence the predictability and stability of visual outcomes after corneal surgery. Some of these biomechanical responses are seen immediately, e.g., following lamellar keratectomy and/or laser ablation.1 Others may manifest in shape instability over time or with further surgery, or result in serious complications such as wound dehiscence, scarring, haze formation, and induction of irregular astigmatism. Corneal biomechanical characteristics often change with wound healing, and also may be better understood in the context of whole eye rigidity.2 In this chapter, we highlight the biochemical and ultrastructural features that most strongly contribute to the biomechanical properties of the normal cornea. Further understanding of these factors provide the basis for improving outcomes and reducing complications of corneal surgery, by identifying individual response outliers and developing strategies for regulating or compensating for these biomechanical features.3 While more familiar to engineers than to most ophthalmologists, we also review the definition of corneal hysteresis and other metrics that have been applied to studies of corneal biomechanics — a subject that encompasses the effects of corneal hydration, regional pachymetry, viscoelasticity and other inherent corneal characteristics that may not yet be fully defined.
Collagen Structure of the Cornea
The tensile integrity and refractive curvature of the cornea is determined in large part by the stroma, which represent the bulk of the corneal thickness. On a weight basis, the stroma is approximately 78% water, 15% collagen and 7% non-collagenous proteins and proteoglycans.4 Approximately 300 collagen lamellae, spanning from limbus to limbus, comprise the center of the cornea.5 This number increases to about 500 as the cornea thickens toward the periphery.4,5 Presumably, this occurs from branching of the lamellae, with some lamellae branches merging with others.6 Branching is seen more extensively in the corneal periphery, where there is primarily a circumferential
orientation of the fibrils.7,8 Branching and interlacing of lamellae has been implicated to play an important role in corneal tensile strength.9
The orientation and spacing of the collagen fibrils appears to be controlled by stromal proteoglycans. Swelling studies have shown that the interlamellar adhesive strength of the central cornea depends upon proteoglycan bonding, whereas branching and interlacing of lamellae provides additional adhesive strength peripherally.7 Changes in the proteoglycan matrix may explain the increased pliability of the central cornea in keratoconus and may potentially impact the corneal response to keratorefractive surgery, contact lens wear and tonometric testing.10
The anterior-most stromal lamellae have oblique branching and interweaving fibers that insert into Bowman’s layer.11 Because of these features, the anterior stroma swells less and is about 25% stiffer than its posterior counterpart.12 Similarly, as there is greater interlacing of peripheral fibers, swelling of the peripheral cornea is usually less than in the central stroma.13 These findings suggest that peripheral and/or posterior incisional surgery may have less of a profound impact on corneal biomechanics than anterior, central surgery (Table 1-1).
It appears that corneal shape is not determined on a random basis, but results from a steady state balance between the biomechanical properties of the cornea and intraocular pressure (IOP).14 The cornea assumes the shape for which its potential energy content is minimal and for which its stromal fibrils are in a relatively relaxed state, as a function of variables such as tissue elasticity, thickness, fibril length, rate of change of IOP, among others. External physiologic corneal stresses, such as from normal blinking or diurnal variation in IOP, and non-physiologic corneal stresses, caused by increases in IOP from forceful lid closure or rubbing, may potentially impact the corneal shape. However, normal corneas have been found to show low extensibility, measured by changes in anterior surface sagittal height, for a wide range of physiologic conditions and even with marked elevations in IOP in order to maintain refractive stability.15 Conversely, when the corneal biomechanical properties are altered via incisional surgery
TABLE 1-1: Local variation in corneal lamellar ultrastructure
Collagen lamellae in the peripheral cornea:
1.Greater number
2.Greater branching and interlacing
3.Circumferential orientation
4.Greater resistance to swelling
Collagen lamellae in the anterior cornea:
1.Anterior strands insert into Bowman’s layer
2.Greater proteoglycan bonding centrally
3.Greater stiffness than posterior cornea