Corneal topography is a non-invasive medical imaging technique for mapping the surface curvature of the cornea, the outer structure of the eye. This procedure may be carried out with a Pentacam, which uses a rotating camera to create a 3D image of the anterior of the eye. This second edition has been fully updated to provide the latest developments in corneal topography and tomography using the Pentacam machine. Beginning with an introduction, the following sections describe the fundamentals of corneal topography and use of the Pentacam with different ophthalmic disorders. With nearly 250 high quality, colour images and illustrations, this concise guide is especially useful to graduate and postgraduate students in learning how to read and interpret corneal topography.
The second edition of this internationally book concentrates on corneal topography and tomography with the very advanced machine ""The Pentacam HR."" It is a pioneer book in this field. Basics of both corneal topography and tomography are well discussed in details according to Pentacam system. New chapter on Corneal Topography in Cataract Surgery is added in this edition with modifications in some chapters such as Curvature Maps/Corneal Power Maps, Keratoectasia, Topographical Criteria and Patterns of Keratoconus, The Hotspot Syndrome and Topographical Patterns of Irregular Astigmatism. Excell.
The new edition of this leading text atlas on corneal topography has been updated to include the latest advances in technology, such as Pentacam and Orbscan. The principles and theory underlying each technology are first clearly explained, and clinical applications are then examined. The authors describe how to use the different technologies and devices, explain the clinical readout with illustrations of normal corneal topography, discuss applications and findings in common disease states, and present the appearances after various corneal surgical procedures. The pros and cons of each system are highlighted. This up-to-date, superbly illustrated book is the most comprehensive guide to corneal topography currently available. It is anticipated that this second edition will become the seminal corneal topography textbook for all with an interest in corneal disease and its management, and refractive surgery.
The third edition of this bestselling book has been fully revised to present ophthalmologists with the latest advances in the interpretation of corneal topography using the Pentacam.
While lecturing in recent months at a number of prominent institutions, I asked some of the residents and fellows whether and how they might benefit from a book on corneal biomechanics. The typical response was the look of a deer caught in the headlights as they tried to intuit the “appropriate” answer, but had little understanding or insight as to why this would be an important and useful knowledge base for them now, or in the future. I then posed the question differently. “Would a book that explained corneal biomechanical principles and testing devices and their application in detecting eyes at risk for developing keratoconus and post-LASIK ectasia, understanding the biomechanical impact of specific types of keratorefractive surgery and riboflavin UV-A corneal collagen cross-linking, and the impact of corneal biomechanics on the fidelity of intraocular pressure measurement and risk for glaucoma progression be of interest?” Framed in this context, the answer I got was a resounding, “Yes!” Therein lies a fundamental disconnect that highlights both the opportunity and need to educate all ophthalmologists about this nascent field. This comprehensive book is strengthened by the breadth of contributions from leading experts around the world and provides an important resource for ophthalmologists at all levels of training and experience. It gives a panoramic snapshot of our understanding of corneal biomechanics today, bridging the gap between theoretical principles, testing devices that are commercially available and in development as well as current and potential future clinical applications. While there has been a long-held appreciation that all types of keratorefractive surgery have an impact and interdependence on corneal biomechanics and wound healing, the initial finite element analyses that were applied to understand radial keratotomy were limited by incorrect assumptions that the cornea was a linear, elastic, homogenous, isotropic material.1 With the advent of excimer laser vision correction, critical observations indicated that Munnerlyn’s theoretic ablation profiles did not account for either lower or higher order (e.g. spherical aberration) refractive outcomes,2 suggesting that there were important components missing from the equation—e.g., corneal biomechanics and wound healing. In a seminal editorial, Roberts3 pointed out that the cornea is not a piece of plastic, but rather a material with viscoelastic qualities. Since that time, much has been learned about spatial and depth- related patterns of collagen orientation and interweaving, as well as the biomechanical response to different keratorefractive surgeries that sever tension-bearing lamellae, as the cornea responds to and redistributes stress induced by IOP, hydration, eye rubbing, blinking and extraocular muscle forces.3-6 The first reports of post-LASIK ectasia7 highlighted the need to identify a biomechanical signature of early keratoconus as well as corneas at high risk of developing ectasia irrespective of their current topography or tomography. The introduction of two instruments into clinical use—the Ocular Response Analyzer (ORA) and the Corneal Visualization Scheimpflug Technology (Corvis ST)—that allow measurement of various biomechanical metrics further catapulted the field. The availability of these instruments in routine clinical settings allowed the systematic study of the effect of age, collagen disorders, collagen cross-linking, corneal rings, flaps of various depths, contour, sidecut angulation, pockets, and flockets, just to name of few. Future application of biomechanics to the sclera may improve our understanding of the development and prevention of myopia, as well as scleral surgeries and treatments under development for presbyopia. It was appreciated by Goldmann and Schmidt that corneal thickness and curvature would influence the measurement of applanation tonometry. The recent ability to measure some corneal biomechanical metrics have led to IOP measurement that may be more immune both to their influence and the impact of central corneal thickness (CCT). Certain chapters in this book explain how a thin cornea could be stiffer than a thick one and that stiffness is also impacted by IOP, thereby precluding simplistic attempts to adjust IOP measurements using nomograms based upon CCT alone. Also highlighted is how corneal hysteresis, the ability of the cornea to absorb and dissipate energy during the bidirectional applanation response to a linear Gaussian air puff, appears to be an independent risk factor for glaucoma progression and rate of progression.9,10 This comprehensive book starts out with a section devoted to outlining basic biomechanical principles and theories, teaching us the language of what Dupps11 has referred to as “mechanospeak”, thus providing a context and common vocabulary to better comprehend the following chapters. By first defining basic concepts such as stress-strain relationships and creep, this theoretical basis is later applied to explain the pathogenesis of corneal diseases, e.g., explaining how a focal abnormality in corneal biomechanical properties precipitates a cycle of decompensation and localized thinning and steepening, clinically expressed as ectasia progression. These early chapters further detail biomechanical differences between in-vivo and ex-vivo testing, between human and animal corneas and sclera, and between methods of testing. The second section provides a thorough description of two FDA-approved devices to measure corneal biomechanics in the clinic (i.e., the ORA and the Corvis ST), as well as an overview of potential future technologies, including OCT with air puff stimulus, ocular pulse elastography, and Brilloiun microscopy. The third and final section of the book is a thorough treatise on how to interpret the metrics derived from the waveform provided by available clinical devices; their adjunct use in ectasia risk screening; the comparative biomechanical impact of various keratorefractive surgeries and corneal procedures such as PRK, LASIK, SMILE, and corneal collagen cross-linking; the impact of corneal biomechanics on IOP measurement; and potential biomechanical markers of enhanced susceptibility to glaucoma progression. This compendium of our current knowledge of corneal biomechanics, its measurement and application, provides a strong foundation to more fully understand advances in keratorefractive and corneal surgery, diseases, and treatments, all of which are interdependent on and influence inherent corneal biomechanical properties and behavior. Both the robust aspects and limitations of our current understanding are presented, including the challenge of creating accurate and predictive finite element models that incorporate the impact of IOP, corneal thickness, geometry, and scleral properties on corneal biomechanics. This book provides a key allowing clinical ophthalmologists and researchers to grasp the basics and nuances of this exciting field and to shape it as it evolves in the future.
Corneal topography is a non-invasive medical imaging technique for mapping the surface curvature of the cornea, the outer structure of the eye. This procedure may be carried out with a Pentacam, which uses a rotating camera to create a 3D image of the anterior of the eye. This second edition has been fully revised to present ophthalmologists with the latest advances in the interpretation of corneal topography using the Pentacam. Beginning with discussion on various devices that may be used for corneal topography, the following sections explain accurate interpretation of the images for diagnosis and treatment. The new edition includes two new chapters on the use of Pentacam topography for refractive surgery patients. The final section presents clinical case studies to assist understanding. Key points New edition presenting latest advances in interpretation of Pentacam topography Includes two new chapters on Pentacam for refractive surgery patients Features case studies to enhance understanding Previous edition published in 2010
Corneal tomography is a non-invasive medical imaging technique for mapping the surface curvature of the cornea, the outer structure of the eye. This procedure may be carried out with a Pentacam, which uses a rotating camera to create a 3D image of the anterior of the eye. This third edition has been fully updated to provide the latest developments in corneal tomography using the Pentacam system. Beginning with an introduction, the following sections cover corneal maps and profiles, corneal refraction, Wavefront analysis, systematic interpretation of corneal tomography, and corneal tomography in ectatic corneal diseases. The final section explains the Holladay Report, and corneal tomography and aberrometry in cataract surgery. Presented in a step by step format the new edition of this popular manual also includes discussion on false positives and false negatives. Authored by recognised expert Mazen M Sinjab, the book features nearly 350 high quality, colour images and illustrations. Key points Fully revised, third edition presenting latest advances in corneal tomography using the Pentacam system Presented in step by step format with nearly 350 images and illustrations Authored by recognised expert Mazen M Sinjab Previous edition (9789350255759) published in 2012
Designed to be used as a quick reference, this fourth edition of the Clinical Manual of Contact Lenses allows readers to easily find the topic and information they need without having to search through an entire chapter to find it. Rigid gas permeable lens design and fitting, soft lens problem-solving, astigmatic management, and bifocal correction are just a few of the subjects covered in this manual. Each chapter includes sample cases to reinforce and demonstrate the practical nature of the topic, with nomograms and proficiency checklists summarizing and emphasizing the important points. With this guide, students and practitioners will have a dependable resource to help fit, evaluate, and troubleshoot any contact lenses, especially specialty designs for years to come.
