With the increased interest in refractive surgery by the ophthalmic community in the past 20 years, and increased awareness of the dangers of “Ectasia' after LASIK' in those who go undiagnosed, keratoconus has been catapulted from an obscure disease to one that is now recognized and managed by the vast majority of practicing anterior segment specialists. This renewed interest in this disease has spurred voluminous research into its early detection, underlying biomechanics, genetics and surgical management.

Whereas 25 years ago, slit-lamp evaluation and corneoscopy was adequate to make a diagnosis of keratoconus, in 2010 videokeratography, wavefront analysis, Scheimpflug tomography, ocular surface tomography (OCT), ultrasonic pachymetry, epithelial ultrasound and corneal hysteresis are all used by different clinicians to better diagnose early forms of the disorder. There have also been huge strides in our understanding of the genetics of the disease which begs the question whether there might be a molecular genetic test for diagnosis in the not too distant future.

In the past the only options in management for keratoconus patients was rigid contact lenses or corneal transplants. Now there are a wide variety of new surgical options which include intracorneal rings, Phakic intraocular lenses, topographic guided photorefractive keratectomy, improved lamellar transplant techniques, femtosecond laser corneal transplants and collagen corneal cross-linking to prevent the progression of the disorder.

In this book Dr Barbara has put together a distinguished panel of experts in the diagnosis and management of keratoconus. Dr Barbara and his colleagues should be congratulated for doing an excellent job in outlining the management options and its attendant challenges for clinicians managing patients with keratoconus.

This book will be of great benefit to those who manage keratoconus now and in the future and ultimately the benefit should be realized by keratoconus patients who struggle daily with the challenge of achieving good vision.

Many experts in the various fields of keratoconus were involved in the preparation of this book, and many of the authors are outstanding international authorities in the field of cornea studies and treatment, such as Ioannis G Pallikaris, Jes Mortensen, Francois Malecaze, Cynthia J Roberts, Renato Ambrósio Junior and George D Kymionis. Several others are inventors of the most advanced technologies, such as Massimo Busin, Paulo Ferrara, Albert Daxer and Dan Z Reinstein, whose important contributions to our understanding and treatment of keratoconus are included in this book. The internationally recognized expert in keratoconus, Yaron S Rabinowitz, generously wrote the Foreword to this book.

Although I cannot mention here all of the esteemed authors and co-authors without whose help this book could not have been published, I would like to take this opportunity to extend my sincere gratitude to all of them.

Occasionally, diagnosis of keratoconus remains challenging even with the use of the above-mentioned technologies, whereby additional techniques may provide more information and that can facilitate the task. All of these technologies are reviewed in the chapters of Section 2 of this book. Higher order aberrations, which increase in keratoconus and cause both degradation of the quality of vision and glare, may be utilized for the diagnosis of keratoconus, an approach that is addressed in a separate chapter. Another means of keratoconus diagnosis is based on epithelial thickness, as measured by Artemis VHF digital ultrasound: the use of epithelial thickness profiles is addressed as well.

Corneal biomechanics are receiving a great deal of attention in refractive surgery and in glaucoma diagnosis and management. For the first time, we have a tool available, the ocular response analyzer (ORA), for measuring corneal biomechanics in vivo, such as corneal hysteresis (CH) and the corneal resistance factor (CRF), which are lower in keratoconic corneas than in normal corneas. There are two chapters in this book that deal with the issue of corneal biomechanics: one deals with ORA and keratoconus and the other deals with the biomechanical decompensation in keratoconus.

The emergence of all of these new diagnostic tools and treatment modalities and the resulting shifts in our approach to keratoconus suggest the need for a comprehensive overview coupled with an in-depth consideration of these developments. Nevertheless, the clinical aspects of keratoconus should not escape our attention; hence, there is one chapter devoted to this essential issue.

Is the frequency of keratoconus increasing or are we simply better equipped to conduct diagnosis due to these newly developed diagnostic tools? A chapter on the epidemiology and a chapter on the genetics of keratoconus consider this question. However, I was astonished by the scarcity of new epidemiological studies; these chapters clearly demonstrate the need for further studies.

Early diagnosis is becoming increasingly important, now that there is a way to stop the progression of this disease, which has been — and remains — the main cause for performing corneal graft in the Western world. From here on, ophthalmologists and optometrists may be found legally liable for missing or delaying a diagnosis of progressive keratoconus, since proper diagnosis coupled with CXL treatment can prevent further disease progression. Furthermore, there are increasing clues that eye rubbing is an important factor in the development and progression of the disease among keratoconic patients. A significantly high level of association has been found between keratoconus and allergy, itch and eye rubbing in teenage and adult patients (see chapter 4 in this book). It is our role as ophthalmologists to warn these patients against eye rubbing, explain the importance of avoiding any eye rubbing and to give the medical treatment that can help reduce the symptoms of allergic external eye diseases. Even when such medical treatments are not sufficient to totally suppress this symptom, I encourage patients 17to find other remedies to reduce this need, such as washing the eyes with cold water or instilling cold artificial tears without preservatives. Thus, we have a role in preventing and stopping the progression of keratoconus.

Inflammatory processes are associated with causing or aggravating keratoconus (see chapter 3). Do the rigid gas permeable (RGP) contact lenses, particularly if poorly fitted, cause keratoconus, by aggravating the inflammatory reaction in keratoconic corneas? This issue still remains an open-ended question.

New treatment modalities, such as corneal collagen cross-linking (CXL) by riboflavin and UVA, aim to stop the progression of the disease. Since the first report on this modality in 2003, which was introduced by Theo Seiler and his group, tens of thousands of patients have been treated using this new technology. In 2006, there were only 6 published reports on this technology; in 2009, 47 reports were found, and new reports are presented in every conference dealing with the cornea and keratoconus. As you will see in the relevant chapter in this book, CXL proved not only to stop the progression of the disease, but in most cases it also improved the uncorrected visual acuity and the best spectacle corrected visual acuity, and reduced myopia, astigmatism, K readings and high order aberrations.

Performing this procedure on the pediatric population, however, is a hot issue, because we don't know yet if it is best to wait for the progression of keratoconus or if it is better to perform the procedure immediately on diagnosis and not to wait for documented progression, as is done with the adult population. The fear is of rapid progression of the disease, which may occur in this group. Currently, there is only one study, by E Albé, on CXL performed in the pediatric population. Dr Albé and her colleagues treated 66 eyes with documented progressive keratoconus in patients whose ages ranged from 9 to 18 years (mean age, 15 years).^* They demonstrated improvement in the uncorrected and best corrected visual acuity, and reduction of the high order aberration. These results are similar to those reported on the adult population. Similar results among pediatric patients were reported by Beatrice E Frueh, in Aegean Cornea, July 2010, Cretes. No study has been published in peer review journals to date. My group is intending to publish the results of CXL for treating 33 eyes of pediatric patients. Hopefully, by the second edition of this book, there will be more studies in peer reviewed journals.

CXL is now in the advanced phases of receiving FDA approval: the preliminary results of a study directed by Dr Stutling show results similar to those published in the literature.

In my opinion, despite the apparent improvement in visual acuity in most of the patients following CXL, in order to avoid unrealistic patient expectations, the sole indications presented to the patient should be arresting the progression of the disease.

The debate remains open on whether to remove the epithelium before the instillation of the riboflavin, as advocated by the group of Theo Seiler, or to keep the epithelium, as advocated by Roberto Pinelli and others. In the meantime, the histological data appear to support the approach of epithelium removal.

This revolutionary technology, which parallels the anti-VGF for the treatment of retinal diseases, will continue to progress, as it is currently the only technology available that deals with the cause of keratoconus development, i.e. the weakening of the collagen fibers. New techniques for CXL are emerging, such as using more light intensity 9 mwcm² instead of 3 mcm² and less exposure time, 10 minutes instead of 30 minutes. Other methods include creating an intracorneal pocket by femtosecond laser, introducing the riboflavin into this pocket and then exposing the cornea to high density UVA of 9 mvcm² for 10 minutes. Another new CXL technique, introduced by Avedro, uses 30 mvcm² energy for 3 minutes only. Not enough studies are available on the efficacy, safety and long-term results of these new techniques to include them in this textbook. For the same reason, i.e. the absence of published long-term results, I did not include a chapter on Conductive Keratoplasty as a tool for remolding the keratoconic cornea even when combined with CXL.

In the future, other modalities or techniques will probably be developed for halting the progression of keratoconus, such as eye drops for collagen corneal cross-linking; however, gene therapy will probably be the best method.

Fifteen years ago, the only treatment we could offer a (mainly RGP)-contact lens intolerant patient with unsatisfactory visual acuity with glasses was penetrating keratoplasty (PKP), a solution laden with problems, from 18an excessively long waiting list to many long days of rehabilitation, not to mention the risks associated with postoperative complications and the likelihood of postoperative astigmatism.

In the past, we used to address problems of high astigmatism by partial correction with glasses, relaxing incisions, and contact lenses (again). However, since about 15 years ago, we started enjoying very high rates of success with the excimer laser, mainly LASIK. High astigmatism may be a sign of recurrent keratoconus, and it is unclear whether the LASIK plays a role in accelerating the recurrence. In these cases, the use of intrastromal corneal rings, which is reviewed in a chapter herein, may reduce myopia, as well as regular and irregular astigmatism after PKP. I personally have had a few of such cases, with acceptable outcomes.

Despite technological improvements in PKP techniques, the introduction of the Intralase assisted PKP and the Big-Bubble technique for deep lamellar keratoplasty (DALK), see relevant chapter, we still try to avoid PKP and DALK, keeping them as last resort treatments for advanced keratoconic scarred corneas unresponsive to other treatment modalities.

Now we can also offer contact lens intolerant patients a variety of contact lenses that are easier to tolerate, such as soft keratoconus lenses, new designs of piggyback (soft contact lenses with a central depression for the RGP contact lens) mini scleral lenses, etc. These varieties of contact lenses provide options for restoring satisfactory visual acuity (VA) to these patients.

If even these contact lenses are not tolerated by these patients, we may now offer various procedures other than PKP: Intrastromal corneal rings (ICRS), and Anterior lamellar keratoplasty (ALK, see chapters 15 and 18). Even photorefractive keratectomy has been reported to render positive results in these cases (see chapter 14). In addition, phakic intraocular lenses may be used to improve VA in keratoconic patients (see chapter 20).

ICRS are widely accepted as a tool for vision improvement in contact lens intolerant keratoconic patients with unsatisfactory VA with glasses, ICRS implantation not only improves the quantitative metrics such as visual acuity and refraction, but also has a positive impact on the patients' quality of life. Various ICRS are available, such as the Intacs, Intacs SK, Ferrara Rings and the Kerarings (similar to Ferrara Ring, see chapters 15 and 16). There are also the Bisantis corneal rings, but no reports exist in the literature on their use and we do not see any marketing of these rings. An additional type of ICRS is the Myoring, which is a round ICRS inserted in a corneal pocket created by a special automated microkeratome (see the chapter 17).

The combination of ICRS and CXL may have an additive effect, a topic which is covered in the chapter on Intacs.

I hope the reader will find this book both useful and helpful for managing this frustrating disease.

Lastly, I would like to thank all of the authors and co-authors who contributed to the book; without whom, the project of this textbook could not have been completed.