The British OrthoKeratology Society
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The British OrthoKeratology Society
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“Orthokeratology, Principles
and Practice.” I was delighted to be asked to review this textbook but I have to declare an interest; the three authors are friends of mine and I was taught about orthokeratology by John Mountford in 1995. Notwithstanding this I will endeavour to be as objective as possible. There have been very few dedicated textbooks on orthokeratology published. The only one I have in my bookcase is” The Orthokeratology Handbook” by Winkler and Kame, a slim spiral bound book published in 1995. The other references are dedicated chapters in contact lens textbooks notably” Contact Lenses” by Philips and Speedwell and articles in various journals. So the publication of this book has been eagerly awaited especially as it is now a year late. It attempts to give the background to orthokeratology development, design and fitting philosophies, scientific principles behind orthokeratology and patient selection, trial lens fitting and problem solving for the neophyte. The history is fascinating because although orthokeratology has been used for the past 40 years, reverse geometry lenses were first used in 1989 and John Mountford developed the first effective computerised and predictable orthokeratology fitting regime in 1994. This means that the discipline is barely 10 years old and those of us who have been involved in that time have seen many exciting changes, both in lens design and basic philosophy. As with all new disciplines, the practitioner base is small and one of the pleasures for me, when reading the book, was to realise that I was personally acquainted with almost everyone mentioned. Another development which made orthokeratology possible was the availability of corneal topography and this is covered in detail along with a chapter on extended wear with RGP materials. Chapter 4,” Design Variables and Fitting Philosophies of Reverse Geometry Lenses” covers both early designs and most of the present lenses available for myopia. ‘Happy families are all alike; every unhappy family is unhappy in its own way.’ Leo Tolstoy It has been my impression over the years that each generation of orthokeratology lenses performs in the same way despite the differences in design and fitting philosophy. So that the original, single reverse curve lens had a maximum change of -2.25D, the first double reverse curve lenses achieved -3.50D and the latest lenses go up to -5.00D. As each designer has his own fitting philosophy, I suppose that makes orthokeratology lenses “unhappy families”. However in my simple way of thinking, I find it difficult to believe that different designs achieve the same effect by different means so I think that they are “happy families”. I have found at least three areas of research that I wish to pursue after reading this chapter and although it is not essential for the beginner, any experienced practitioner will benefit from reading it. There are some minor errors in the labelling of some of the illustrations which will be corrected in the second printing. The authors say there are five but I could only find three. The three chapters 5, 6 and 9 are really a handbook on orthokeratology fitting. Any practitioner new to the discipline will be able to make a start after reading these chapters. I really wish I had this when I started out. In Chapter 5, patient selection and preliminary examination are covered in detail and although I issue all my patients with a handbook, I am going to revise my paperwork in the light of the suggested information pack. Chapter 6 on trial lens fitting covers three approaches which are empirical, trial lens and corneal response data. There is a fourth approach which is the lens bank which combines the last two with final dispensing from an in-practice inventory. This is the CRT system from Paragon which is discussed in the chapter although not distinguished from the other trial lens systems. The empirical system is discussed at length and the final paragraph states: “Empirical fitting is potentially inefficient, time-consuming and expensive when compared to trial lens fitting with standard spherical RGP fitting (Bennett 1989). It is even less efficient when applied to reverse geometry fitting”. I was told recently that practitioners achieved a 60% first fit with trial lenses but an 80% first fit when the lenses were calculated empirically using a specific design. This lab was not encouraging trial lens fitting. I think the difference in attitude is due to the accuracy of modern topographers. If the lens design is matched to a particular topographer then the results will be good. Trial lens fitting covers almost 30 pages, emphasising its importance in present-day orthokeratology fitting, and gives details of most of the fitting sets available with instructions in their use, topography and fluorescein photographs. You start to see the typical bull's-eye pattern and the differences in small changes in parameters. The importance of post trial topography is emphasised with full-colour photographs of the various results that one is likely to see. One fitting tip that is not present, which I find extremely useful, is that a lens with insufficient sag, a ‘flat’ lens, will ride high after a blink. I have just realised that my main complaint with this textbook is the use of ‘steep’ and ‘flat’ when referring to the orthokeratology fits. With the vast majority of lens designs one cannot alter the sag without changing other parameters such as the BOZR. We have therefore fallen into the habit into describing lenses as a flat or steep fitting when we should be describing them in terms of the sag i.e. either excessive or insufficient. A lens with insufficient sag will touch the central cornea and pivot upwards on a blink, this causes the traditional ”Smiley Face” pattern topography. Chapter 9 is the third one the potential Orthokeratologist should read as it covers the lens delivery, aftercare routine and problem solving. The only thing that is missing is information on how to organise your patient record cards. I have found over the years that specific recording sheets had to be made up so that interpretation of the many fitting and aftercare visits could be easily achieved. Corneal and refractive changes due to orthokeratology are covered in chapter 7 in great detail where the authors have bought together a lot of the information previously published in separate articles. This I think is essential reading for the experienced practitioner and recent research into histological changes caused by orthokeratology confirm the preliminary findings. Chapters 8 and 10 are for the hardcore only. They cover computerised modelling and a model of forces in orthokeratology. This is fascinating stuff but I have to admit that I have not yet finished chapter 10 after three attempts. The last brief chapter is entitled the future, and the progress in orthokeratology is so fast that in the year it has taken for this book to be published, two or even three advances have been made which are not mentioned. The first are designs for hyperopia which can achieve changes up to +3.00D, the second are designs for presbyopia which induce a centre near, blending to a distance periphery and the third, which was briefly discussed and dismissed, are designs for high myopic correction up to -10.00D. So, the first question is “Would I buy this book?” Well, I already have; I was the first in line when it went on sale at the BCLA in May. The second question is ”Should you buy this book?” If you are interested in fitting orthokeratology lenses or are already an experienced orthokeratology practitioner, I think it is essential reading. And I am not alone, it was a fast seller at BCLA, it sold out at the 2nd Global Orthokeratology Symposium in Toronto in July and I understand that the first print run has sold out and it is being reprinted. The following is a quote from an experienced
orthokeratology practitioner in America who does not have any personal contact
with the authors. “I think that anyone who is fitting or considering
fitting, orthokeratology lenses would find this text extremely valuable. Not
only from a "How To" point of view, but from the when, where, how, and why
perspective. The in depth evaluations of history, topography, and lens
materials show that the authors have considered every aspect of this exciting
field within the realm of contact lenses. I concur. Copies can be obtained from
Andrew McNeil
Basil Bloom |
Copyright © 2005
The British Orthokeratology Society
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